fresh leaves ranged from 2.4 µmol/g ( Chrysopogon) to

cluster analysis, where the fold change values of all

11.8 µmol/g ( Digitaria and Thysanolaena) and increased

parameters were taken into consideration (Figures 3a‒3f).

Table 6. Electrolyte leakage (%) of grasses under treatments of 0, 100 and 200 mM NaCl solutions for 3, 6 and 9 days.

Grass

Concentration of NaCl (mM/L) and duration of treatment

3 days1

6 days2

9 days3

0

100

200

0

100

200

0

100

200

Arundo

14.1 ±0.5 21.2 ±0.1 25.4 ±0.5

14.1 ±0.6 23.1 ±0.3 24.9 ±0.2

14.3 ±0.2 22.9 ±0.4 26.7 ±0.3

Axonopus

10.1 ±0.7 12.2 ±0.3 14.3 ±0.3

10.3 ±0.3 13.4 ±0.2 15.6 ±0.3

10.6 ±0.3 14.3 ±0.6 17.2 ±0.3

Capillipedium

8.7 ±0.1

14.3 ±0.5 16.7 ±0.6

9.1 ±0.3

15.1 ±0.3 17.8 ±0.3

8.8 ±0.3

16.2 ±0.6 18.6 ±0.3

Chrysopogon

5.2 ±0.5

6.7 ±0.3

8.1 ±0.3

6.1 ±0.5

8.2 ±0.4

9.7 ±0.3

5.5 ±0.3

7.8 ±0.3

10.6 ±0.2

Cynodon

11.9 ±0.9 12.1 ±0.4 13.2 ±0.5

12.2 ±0.4 13.2 ±0.5 13.9 ±0.3

10.8 ±0.4 12.9 ±0.4 14.3 ±0.4

Digitaria

11.2 ±0.8 13.4 ±0.3 14.5 ±0.3

10.7 ±0.7 14.5 ±0.5 15.6 ±0.3

11.1 ±0.4 15.2 ±0.2 17.2 ±0.3

Arundinella

5.2 ±0.6

6.2 ±0.2

6.5 ±0.2

5.1 ±0.2

6.1 ±0.3

6.7 ±0.1

4.9 ±0.3

5.5 ±0.3

7.1 ±0.3

Eragrostis

10.1 ±0.9 13.1 ±0.2 14.5 ±0.3

10.4 ±0.3 14.2 ±0.4 15.4 ±0.2

10.6 ±0.3 14.5 ±0.2 16.7 ±0.4

Imperata

14.3 ±1.1 16.1 ±0.3 16.5 ±0.3

14.5 ±0.4 15.8 ±0.3 17.2 ±0.3

14.9 ±0.4 18.8 ±0.3 19.7 ±0.3

Oplismenus

13.4 ±0.7 16.1 ±0.4 17.2 ±0.4

13.1 ±0.3 16.8 ±0.2 18.1 ±0.4

13.4 ±0.2 17.5 ±0.2 19.2 ±0.6

Setaria

15.1 ±0.8 17.2 ±0.2 19.3 ±0.4

15.4 ±0.2 18.9 ±0.4 21.3 ±0.4

16.1 ±0.3 24.3 ±0.3 26.7 ±0.5

Thysanolaena

7.6 ±0.6

8.1 ±0.1

9.7 ±0.5

7.3 ±0.3

9.5 ±0.3

11.2 ±0.3

7.8 ±0.4

10.1 ±0.4 13.4 ±0.4

1LSD (P≤0.05) Species = 2.6; Treatment = 1.3. 2LSD (P≤0.05) Species = 2.53; Treatment = 1.27. 3LSD (P≤0.05) Species = 2.82;

Treatment = 1.41. Values represent Mean ± SD, where n = 3.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

138 S. Roy and U. Chakraborty

Table 7. H2O2 concentration (µmol/g fwt) in grasses under treatment with 0, 100 and 200 mM NaCl solutions for 3, 6 and 9 days.

Grass

Concentration of NaCl (mM/L) and duration of treatment

3 days1

6 days2

9 days3

0

100

200

0

100

200

0

100

200

Arundo

6.5 ±0.1

11.2 ±0.2 13.1 ±0.3

6.6 ±0.4

12.3 ±0.2 15.6 ±0.1

6.7 ±0.3

15.4 ±0.3 18.7 ±0.5

Axonopus

7.2 ±0.3

10.2 ±0.3 14.5 ±0.2

8.1 ±0.1

14.3 ±0.2 17.8 ±0.2

8.3 ±0.1

16.7 ±0.1 21.3 ±0.3

Capillipedium

4.5 ±0.2

5.4 ±0.4

8.7 ±0.2

4.1 ±0.2

6.7 ±0.1

10.9 ±0.3

4.8 ±0.3

8.8 ±0.1

15.4 ±0.5

Chrysopogon

2.5 ±0.8

4.1 ±0.2

7.2 ±0.4

2.1 ±0.3

5.3 ±0.2

9.3 ±0.4

2.7 ±0.1

7.4 ±0.5

11.2 ±0.2

Cynodon

10.1 ±0.7 11.2 ±0.2 13.2 ±0.5

9.7 ±0.4

14.5 ±0.3 17.6 ±0.3 10.3 ±0.4 13.2 ±0.5 18.1 ±0.3

Digitaria

12.1 ±0.8 15.4 ±0.3 17.8 ±0.3 11.7 ±0.5 17.1 ±0.4 23.1 ±0.5 11.9 ±0.1 20.1 ±0.4 24.3 ±0.2

Arundinella

6.8 ±0.5

7.6 ±0.5

8.9 ±0.2

6.6 ±0.6

9.9 ±0.4

11.7 ±0.4

6.5 ±0.4

11.7 ±0.4 15.3 ±0.5

Eragrostis

4.5 ±0.4

4.7 ±0.2

6.7 ±0.2

4.1 ±0.3

6.2 ±0.5

8.4 ±0.1

4.3 ±0.2

7.6 ±0.3

10.9 ±0.2

Imperata

8.7 ±0.3

9.1 ±0.7

10.3 ±0.3

8.2 ±0.3

10.3 ±0.3 13.4 ±0.3

8.6 ±0.4

12.9 ±0.5 15.2 ±0.3

Oplismenus

11.3 ±0.4 14.3 ±0.2 18.7 ±0.3 10.9 ±0.2 16.5 ±0.2 21.8 ±0.1 11.1 ±0.1 17.6 ±0.3 20.1 ±0.5

Setaria

8.5 ±0.5

9.1 ±0.3

9.8 ±0.2

8.1 ±0.3

14.3 ±0.2 17.6 ±0.2

7.9 ±0.8

15.1 ±0.2 18.9 ±0.3

Thysanolaena

11.1 ±0.9 14.5 ±0.2 17.6 ±0.1 12.2 ±0.6 15.2 ±0.3 18.1 ±0.3 12.1 ±0.7 21.5 ±0.3 23.8 ±0.1

1LSD (P≤0.05) Species = 2.1; Treatment = 1.05. 2LSD (P≤0.05) Species = 2.19; Treatment = 1.09. 3LSD (P≤0.05) Species =

2.42; Treatment = 1.21. Values represent Mean ± SD, where n = 3.

Figure 4. Hierarchical cluster analysis of the grasses using the fold change values of relative water content (RWC); proline concentration (PRO); soluble sugar concentration (SUG); membrane lipid peroxidation (malondialdehyde, MDA); electrolyte

leakage (EL); and H2O2 concentration after NaCl treatments (100 mM and 200 mM) for 3, 6 and 9 days. Resulting tree figure was

displayed using Java Treeview after hierarchical cluster analysis through CLUSTER 3.0. The color grids in the cluster analysis represent the relative fold change values (-3 to +3 shown by different colors) of the specific biochemical markers for each of the

individual grasses. For the analysis of salt tolerance, the greenness of the grids for biomarkers like MDA, EL and H2O2 and redness

for RWC, PRO and SUG was considered; which means a species for which the grids are more reddish for RWC, PRO and SUG and

less greenish for MDA, EL and H2O2 could be considered the most tolerant of all. However, this was easily recognized in the cluster

analysis due to grouping of the studied species on the basis of their responses to biochemical markers.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Salinity tolerance of some forage grasses in India 139

The ranges of fold change values in the clusters are

technique to screen out the potential salt-tolerant forage

represented by the colored bars. Results suggested the

grasses.

probable interrelations among biochemical parameters

The 6 biomarkers we selected to analyze the salt-

subjected to NaCl stress and variable salt tolerance

tolerance potential of the forage grasses, namely relative

between all grass genera.

water content (RWC), proline and soluble sugar

Based on their salt sensitivities, the grasses formed 2

concentrations, membrane lipid peroxidation, electrolyte

distinct groups (Figure 4). One group was comprised of

leakage and H2O2 concentration, proved useful in

Axonopus, Chrysopogon, Oplismenus and Thysanolaena.

indicating differences between species in ability to

The remaining grasses with varying response patterns to

tolerate saline conditions both simply and rapidly.

NaCl solutions formed the second group and were

While RWC of any plant always decreases with the

classified into 3 subgroups: Arundo and Capillipedium;

increase in NaCl concentration, a lower decrease in RWC

Arundinella and Setaria; and Digitaria, Cynodon,

is a valuable marker in the selection of salt-tolerant

Eragrostis and Imperata.

species (Ziaf et al. 2009). In our study, lowest decreases

in RWC were observed in Cynodon, Eragrostis and

Discussion

Imperata across all concentrations and durations of NaCl

treatments, identifying them as salt-tolerant species. In

This rapid screening for salinity tolerance in the forage

contrast, accumulation of proline and soluble sugars is

grasses has been attempted as a simple method of

considered to be positively correlated with salinity

identifying the most salt-tolerant grasses for introduction

tolerance (Karsensky and Jonak 2012; Hayat et al. 2012).

into areas with increasing soil salinity and decreasing

Accumulation of higher levels of proline has been

productivity. Previously, Zulkaliph et al. (2013) in their

reported

in

the

halophytes,

Mesembryanthemum

studies with turfgrasses ranked the different species of

crystallinum and Sporobolus virginicus when compared

grasses for salinity tolerance on the basis of shoot and root

with the glycophytes carrot and rice (Thomas et al. 1992;

growth, leaf firing, i.e. yellowing of leaves resulting from

Tada et al. 2014). In the present study, apart from

cell death due to osmotic imbalances, turf color and turf

Axonopus, Chrysopogon and Oplismenus, proline accu-

quality. We estimated salinity tolerance of the grasses

mulation increased in all grasses subjected to NaCl

primarily by a salt sensitivity index (SSI), determined by

treatment. We also observed that soluble sugar accumu-

evaluating the effects of NaCl solutions on leaf discs over

lation decreased in Arundo, Axonopus, Capillipedium,

96 hours. This type of bioassay has been used previously

Oplismenus, Setaria and Thysanolaena across all

in several transgenesis experiments to evaluate the

concentrations of NaCl and durations of exposure. In

tolerances of transgenic plants relative to the wild type

contrast, accumulation of soluble sugars increased in

plants from which they were bioengineered (Bhaskaran

Digitaria, Imperata and Arundinella subjected to NaCl

and Savithramma 2011; Yadav et al. 2012).

treatments for 3, 6 and 9 days. Nedjimi (2011) also

The amount of chlorophyll leached out from the leaf

correlated the accumulation of greater amounts of soluble

discs into the NaCl solution was used as an indicator of

sugars in the forage grass Lygeum spartum with osmotic

the effect of NaCl on leaf tissues. The decrease in

adjustment and protection of membrane stability that

chlorophyll concentration in plants subjected to NaCl

conferred salinity tolerance.

treatment has been inversely correlated with salinity

Increase in malondialdehyde (MDA) concentration,

tolerance. For instance, the decrease in Chlorophyll a:

an indication of lipid peroxidation, is considered

Chlorophyll b ratio in salt-tolerant Najas graminea was

unfavorable for plant health, and plants, which show

lower than in Hydrilla verticillata and Najas indica (Rout

little increase in MDA concentration when exposed to

et al. 1997). In the present study, we quantified the

NaCl, are considered to be salt-tolerant (Miller et al.

amount of chlorophyll in the leaf discs in both control and

2010). Marked increases in MDA concentration were

treatment sets and the values were used to reciprocate the

observed in Axonopus, Capillipedium, Chrysopogon and

sensitivity of grasses towards NaCl treatment. Greater salt

Thysanolaena, following exposure to salt. However,

sentivity index values denoted greater susceptibility of the

minimal increase was observed in Cynodon and

grasses towards NaCl. Overall, the results of the bioassay

Eragrostis across all concentrations and durations of

indicated that among the grasses tested, Imperata,

treatment.

Cynodon and Digitaria could be considered as less

Similarly, low electrolyte leakage (EL) and limited

sensitive or resistant on the basis of SSI values at 100 and

increase in H2O2 concentration in response to NaCl

200 mM NaCl. SSI therefore presents an easy and rapid

treatment are also considered as markers of the salt

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

140 S. Roy and U. Chakraborty

tolerance of plants (Mostafa and Tammam 2012).

Eragrostis could be considered salt-tolerant. Thus, while

Accumulation of H2O2 in plants interferes with the normal

individual biochemical markers provide good indications

biochemical processes inside plants. In the present study,

of the degree of salt tolerance of a species, cluster

EL in all grasses increased with the increase in NaCl

analysis, which incorporates the results with several

concentration and duration of treatment. Least EL was

biomarkers, provides a much more reliable indication.

observed in Cynodon, Imperata and Arundinella, which

However, SSI values can provide an easy and rapid tool

could be considered salt-tolerant species in comparison

for the screening of salt tolerance. Based on our screening

with the other grasses. The high increases in H

results, we consider that the selective propagation of the

2O2

concentration

observed

in

Arundo,

Axonopus,

most salt-tolerant species could be utilized for the

Capillipedium and Chrysopogon indicate that these

rejuvenation of native grasslands and also for the

species can be considered susceptible to salination on the

reclamation of salinity infested wastelands.

basis of this trait. Comparatively, low increases in H

2O2

concentration observed in Imperata, Setaria and Cynodon

Acknowledgments

indicate that they can be considered salt-tolerant.

The authors are grateful to CSIR, New Delhi (Award No.

Finally, hierarchical cluster analysis using the software

09/285(0046)/2008-EMR-I) and UGC, ERO, Kolkata

CLUSTER 3.0 was used to represent the inter-relations

(Minor Research Project No. PSW-80/12-13) for the

among the physiological parameters and to align the

financial support which enabled the carrying out of this

grasses on the basis of their salinity tolerance as a similar

work.

type of hierarchical cluster analysis has been performed

to evaluate the natural variation in drought tolerance in

bermuda grass (Shi et al. 2012) and the variation in salt

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(Received for publication 25 August 2016; accepted 3 June 2017; published 30 September 2017)

© 2017

Tropical Grasslands-Forrajes Tropicales is an open-access journal published by Centro Internacional de Agricultura

Tropical (CIAT). This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0

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Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Tropical Grasslands-Forrajes Tropicales (2017) Vol. 5(3):143–152 143

DOI: 10.17138/TGFT(5)143-152

Research Paper

Reduction of sward height in the fall and winter as a strategy to

improve the structure of marandu palisadegrass ( Urochloa

brizantha syn. Brachiaria brizantha cv. Marandu)

Reducción de la altura del pasto en otoño e invierno como estrategia para

mejorar la estructura de una pastura de Urochloa (sin. Brachiaria ) brizantha

cv. Marandu

MANOEL E.R. SANTOS1, MIRIÃ G. SIMPLÍCIO1, GUILHERME P. SILVA2, HERON A. DE OLIVEIRA1,

LUDIÊMILEM K.P. DA COSTA1 AND DIOGO O.C. DE SOUSA1

1 Faculty of Veterinary Medicine, Federal University of Uberlândia, Uberlândia, MG, Brazil. www.ufu.br

2 Animal Science Department, ESALQ, University of São Paulo, Piracicaba, SP, Brazil. www.esalq.usp.br

Abstract

The objective of this study was to identify defoliation strategies that might improve the structure of Urochloa brizantha

(syn. Brachiaria brizantha) cv. Marandu (marandu palisadegrass). The following 3 defoliation strategies were compared

in a plot study: sward kept at 15 cm in fall and winter (W) and 30 cm in spring (Sp) and summer (Su) (15W-30Sp-30Su);

sward kept at 30 cm during the entire experimental period (30W-30Sp-30Su); and sward kept at 45 cm in fall and winter

and 30 cm in spring and summer (45W-30Sp-30Su). The experimental design was completely randomized, with 4

replicates. Plots were cut with shears to the appropriate height weekly in winter and twice weekly in spring, summer and

fall. Tiller density, mean tiller weight, leaf area index, forage mass, percentage of live leaf blades and percentage of

stems were measured every 28 days. Forage mass in winter was directly related to pasture height (P<0.05) but differences

had disappeared by summer (P>0.05). Mean tiller density was independent of cutting height but was higher in spring

and summer than in winter (P<0.05). Mean tiller weight in winter was directly related to cutting height (P<0.05) but

differences had disappeared by summer. The percentage of live leaf blades in the swards was affected by season with

spring>summer>winter and by cutting height in fall/winter with leaf percentage inversely related to cutting height. Stem

percentage in the swards in winter was directly related to cutting height. Grazing studies seem warranted to determine if

these plot results are reflected under grazing conditions and what the impacts are on animal performance.

Keywords: Herbage mass, leaf area index, morphological composition, tillering.

Resumen

El objetivo del estudio, conducido en Uberlândia, Minas Gerais, Brasil, fue identificar estrategias de defoliación con el

fin de mejorar la estructura de una pastura de Urochloa brizantha (sin. Brachiaria brizantha) cv. Marandu. Se compararon 3 estrategias: (1) mantener el pasto a una altura de 15 cm en otoño e invierno (W) y de 30 cm en primavera

(Sp) y verano (Su) (15W-30Sp-30Su); (2) mantener el pasto a una altura de 30 cm durante todo el período experimental

(30W-30Sp-30Su); y (3) mantener el pasto a una altura de 45 cm en otoño e invierno y de 30 cm en primavera y verano

(45W-30Sp-30Su). El diseño experimental fue completamente al azar, con 4 repeticiones. Las parcelas se cortaron con

tijeras a la altura respectiva semanalmente en invierno y 2 veces por semana en primavera, verano y otoño. Cada 28 días

___________

Correspondence: D.O.C. de Sousa, Faculty of Veterinary Medicine,

Federal University of Uberlândia, Campus Umuarama, Av. Pará

1720, Uberlândia CEP 38400-902, MG, Brazil.

Email: diogoolimpio@hotmail.com

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

144 M.E.R. Santos, M.G. Simplício, G.P. Silva, H.A. de Oliveira, L.K.P. da Costa and D.O.C. de Sousa

se midieron la densidad de brotes, el peso medio de los brotes, el índice de área foliar, la masa de forraje, el porcentaje

de hojas vivas y el porcentaje de tallos. La masa forrajera en invierno se relacionó directamente con la altura del pasto

(P<0.05), pero las diferencias desaparecieron en verano (P>0.05). La densidad media de los brotes fue independiente de

la altura de corte, pero fue mayor en primavera y verano que en invierno (P<0.05). El peso medio de los brotes en invierno estuvo directamente relacionado con la altura de corte (P <0.05), pero las diferencias desaparecieron en verano.

El porcentaje de hojas vivas en la pastura se vio afectado por la estación del año, con primavera>verano>invierno y por

la altura de corte en otoño/invierno cuando el porcentaje de hojas estuvo inversamente relacionado con la altura de corte.

El porcentaje de tallos en invierno estuvo directamente relacionado con la altura de corte. Estudios de pastoreo parecen

justificados para determinar si estos resultados, obtenidos a nivel de parcela de corte, se reflejan bajo condiciones de

pastoreo, y cuáles son los impactos en la producción animal.

Palabras clave: Composición morfológica, índice de área foliar, masa forrajera, rebrotes.

Introduction

could result in lower maintenance respiration by the

plants, which would provide greater energy and carbon

Pasture structure is a function of how the organs of the

balance in the sward (Taiz and Zeiger 2012). In contrast,

aerial parts of forage plants are distributed in the pasture,

keeping pasture tall in winter would increase the energy

both vertically (Zanini et al. 2012) and horizontally

needs for survival of individual plants, precisely when

(Barthram et al. 2005). Some parameters used to describe

photosynthesis is at its lowest point.

pasture structure are: sward height, forage mass, volume

Moreover, Santana et al. (2014) suggested that the

and density (Carvalho et al. 2009).

greater shading at the plant base, inherent in taller

Pasture height is highly correlated with forage mass

pastures, would lead to greater leaf senescence at the

and morphological composition (Paula et al. 2012; Nantes

lower canopy stratum, which might inhibit tillering in

et al. 2013), in addition to being a cheap, easy and quick

early spring. On the other hand, pasture grazed short in

measurement. For this reason, average pasture height has

winter would permit greater incidence of light at the base

been recommended as a management criterion for when

of the sward in spring, which should stimulate the

to commence and cease grazing (Silva and Nascimento

appearance of young tillers (Paiva et al. 2012) with better

Júnior 2007). Studies on grazing management strategies,

structural traits (Barbosa et al. 2012).

based on pasture height, enable the understanding of

We therefore hypothesize that, by varying sward

variations in pasture structure, as well as the responses of

height during fall and winter, it may be possible to modify

animals and plants to these variations (Trindade et al.

physiological processes such as photosynthesis and

2007; Fonseca et al. 2012, 2013).

respiration as well as plant development, e.g. tillering and

Sbrissia et al. (2010) suggested that the optimal height

leaf senescence. All these processes, in turn, may change

range for management of marandu palisadegrass

sward structure not only in fall and winter, the seasons in

( Urochloa brizantha syn. Brachiaria brizantha cv.

which plant height is changed, but also in subsequent

Marandu) under continuous grazing during the rainy

ones.

season was 20‒40 cm. However, Santos et al. (2013)

This study was conducted to characterize the structural

suggested that pasture height should be adjusted

changes of a marandu palisadegrass sward maintained at

according to the season of the year to optimize the

various sward heights in fall and winter, and kept at a

productivity of the pasture. Other studies, e.g. Sbrissia

constant height in spring and summer. This knowledge

and Silva (2008) and Giacomini et al. (2009), indicated

should prove beneficial in formulating recommendations

that plant development is often affected by interactions

regarding defoliation strategies for this forage plant

between defoliation management strategies and season of

throughout the year.

the year, which suggests that the success of a particular

management strategy might differ between seasons. On

Materials and Methods

the basis of these findings, we conclude that grazing

management strategies should be flexible over the year

The experiment was conducted from March 2013 to

and vary with seasonal conditions.

March 2014, on the Capim Branco farm, belonging to the

Maintaining the sward shorter during winter, the

Faculty of Veterinary Medicine of the Federal University

season with adverse climate and in which the plant has the

of Uberlândia, in Uberlândia, MG, Brazil (18º53’19” S,

lowest rate of photosynthesis (Lara and Pedreira 2011a),

48°20’57” W; 776 masl). The climate in the region of

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Sward height and yield of palisadegrass 145

Uberlândia, according to the Köppen (1948) classifi-

Before the experiment commenced, soil samples from

cation, is a Cwa altitude tropical type, with mild and dry

the 0‒10 cm layer were collected and analyzed, revealing

winters and well defined dry and rainy seasons. The aver-

the following chemical properties: pH in H2O - 6.1; P -

age annual temperature is 22.3 ºC, with mean maximum

9.4 mg/dm3 (Mehlich-1); K+ - 156 mg/dm3; Ca2+ - 5.5

and minimum values of 23.9 and 19.3 ºC, respectively.

cmolc/dm3; Mg2+ - 1.7 cmolc/dm3; Al3+ - 0.0 cmolc/

Average annual precipitation is 1,584 mm.

dm3 (KCl 1 mol/L); effective CEC - 7.6; CEC at pH 7.0 -

The experiment was developed on a pasture of

10.3; and base saturation - 74%. Based on these results,

Urochloa brizantha syn. Brachiaria brizantha cv.

35.5 kg P/ha as single superphosphate, 50 kg N/ha as urea

Marandu (palisadegrass), established in the year 2000,

and 41.5 kg K/ha as KCl were broadcast on the plots in

and well managed with cattle. Twelve plots (experimental

February 2013. These same amounts were applied again

units) with an area of 12 m2 each were used. A border area

in January 2014.

of 0.25 m wide was discarded leaving a usable area of

Three defoliation strategies were evaluated, charac-

8.75 m2 on each plot for data collection.

terized by the heights at which the marandu palisadegrass

Climatic conditions during the experimental period

sward was maintained during fall and winter (15, 30 and

were monitored at the meteorological station, located

45 cm), with a standard height of 30 cm during spring and

approximately 200 m from the experimental area (Figures

summer. To maintain the grass at these heights, the

1 and 2).

swards were cut with pruning shears once a week in

winter and twice a week during spring, summer and fall.

This approach aimed to ensure that the actual heights of

the canopies remained within 100‒110% of the desired

values. The first strategy, with marandu palisadegrass

maintained at 15 cm in fall and winter and 30 cm in spring

and summer, equated with heavy defoliation during

winter and moderate defoliation subsequently. For the

second strategy the pasture was maintained at 30 cm

during the entire experimental period, according to the

recommendations of Sbrissia and Silva (2008), i.e.

moderate defoliation throughout. The third strategy

consisted of maintaining the grass at 45 cm in fall and

winter, i.e. only light defoliation, and at 30 cm in spring

and summer.

Figure 1. Monthly mean minimum and maximum temperatures

The experimental period during which pasture

and precipitation from March 2013 to March 2014. The seasons

measurements occurred was divided into winter (July‒

are: winter, July‒September 2013; spring, October‒December

September 2013), spring (October‒December 2013) and

2013; and summer, January‒March 2014.

summer (January‒March 2014). The experimental design

was completely randomized, with 4 replicates.

The fall (March‒June 2013) was considered the period

of acclimation of the plants to the particular sward heights.

From June 2013, at 28-day intervals, tiller density was

evaluated by counting the live tillers within two 50 × 25 cm

metal frames randomly located in each experimental unit.

The data were grouped according to season.

Monthly, in each season of the year and on each plot,

a sample of 50 tillers with average length similar to the

sward height was chosen. These tillers were harvested at

ground level and divided into live leaf blade, dead leaf

blade and live stem (stem + leaf sheath). Parts of the leaf

Figure 2. Summary of the water balance in the soil from

blade that did not show signs of senescence (green

January 2013 to April 2014. Arrows indicate the time when

organ) were incorporated into the live leaf blade

fertilizer was applied. The seasons are: winter, July‒September

fraction. Any part of the leaf blade with a yellowish tone

2013; spring, October‒December 2013; and summer, January‒

and or necrosis was considered dead leaf blade. Each

March 2014. DEF (-1) = Deficit; EXC = Excess.

sub-sample (live leaf blade, dead leaf blade and live

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

146 M.E.R. Santos, M.G. Simplício, G.P. Silva, H.A. de Oliveira, L.K.P. da Costa and D.O.C. de Sousa

stem) from the 50 tillers was collected in a single paper

bag, dried in an oven at 65 ºC for 72 h and then weighed

together, in order to obtain the masses of the morpho-

logical components, and the mean weight of tillers was

calculated. The masses of the sward morphological

components were obtained by the following formula:

FM = NT × TM, in which FM is the forage mass or the

mass of the plant morphological component (kg DM/ha);

NT is the number of tillers/10,000 m2; and TM is the

mass of the morphological component of the tiller (kg

DM/tiller). The masses of the plant morphological

components were expressed as percentages of the total

forage mass.

After harvesting the tillers in each plot, 50 live leaf

Figure 3. Effects of time of year on mean tiller density in

blades were also collected at random and placed in plastic

palisadegrass swards.

bags. A small portion of the extremities of the leaf blades

Means followed by the same letter do not differ (P>0.05).

(apex and base) was cut and discarded, so as to generate

an approximately rectangular leaf blade segment. The

Mean tiller weight was influenced by defoliation

width and length of each segment were measured, and the

strategy (P = 0.016) and by the interaction between this

leaf area of the leaf blade segments was calculated as the

factor and season of the year (P = 0.024). In winter, tiller

product of these dimensions. These segments were placed

weight was greater in the sward maintained at 45 cm in

in a forced-ventilation oven at 65 ºC for 72 h and then

fall/winter than in that at 15 cm, while in spring, the sward

weighed. With these data, the specific leaf area (cm² leaf

kept at 45 cm in fall/winter produced heavier tillers than

blade/g dry leaf blade) was calculated. The leaf area index

that at 30 cm in fall/winter. However, by summer, mean

of each tiller was calculated as the product of the specific

tiller weight was similar for all defoliation strategies in

leaf area and the live leaf blade mass of the tiller. The

fall/winter (Figure 4). The sward maintained at 45 cm in

pasture leaf area index, however, was obtained by

fall/winter produced similar sized tillers throughout

multiplying the leaf area of the tiller by the number of

(P>0.05), while the 30 cm sward in winter produced its

tillers per ha.

smallest tillers in spring (P<0.05) and the 15 cm sward in

For the data analysis, the results were grouped

winter produced progressively bigger tillers from winter

according to the season of the year (winter, spring and

to summer (P<0.05).

summer). Initially, the dataset was analyzed to check if it

Forage mass in the marandu palisadegrass was

met the assumptions of the analysis of variance (normality

influenced by season of the year (P = 0.013) and by the

and homogeneity). The data were then analyzed using the

interaction between this factor and defoliation strategy (P

MIXED procedure (mixed models) of the SAS®

= 0.009). In winter, forage mass was greatest in the sward

(Statistical Analysis System) statistical package, version

maintained at 45 cm, intermediate in the sward

9.2. The variance and covariance matrix was chosen using

maintained at 30 cm, and lowest in the sward maintained

Akaike’s Information Criterion (Wolfinger 1993). The

at 15 cm in fall/winter. In spring, forage mass in the sward

treatment means were estimated using the “LSMEANS”

maintained at 45 cm in fall/winter was greater than in that

option, and compared with each other by Student’s t test

kept at 30 cm in fall/winter. However, forage mass in

at 5% probability.

summer was independent of defoliation strategy in

fall/winter (Figure 5).

Results

The percentage of live leaf blades (PLLB) in the forage

mass was influenced by both season of the year (P<0.0001)

Tiller density in the palisadegrass was influenced only by

and defoliation strategy (P = 0.010). Overall PLLB

season of the year (P = 0.035), with fewer tillers in winter

followed the order: spring>summer>winter (Figure 6A),

than in spring and summer (Figure 3).

and was inversely related to height in winter (Figure 6B).

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Sward height and yield of palisadegrass 147

Figure 4. Effects of time of year and defoliation management on mean tiller weight in palisadegrass swards.

45W-30Sp-30Su: sward kept at 45 cm in winter and 30 cm in spring and summer; 30W-30Sp-30Su: sward kept at 30 cm in winter,

spring and summer; and 15W-30Sp-30Su: sward kept at 15 cm in winter and 30 cm in spring and summer. Lowercase letters compare

defoliation strategies within seasons of the year, and uppercase letters compare seasons of the year within each defoliation strategy.

Means followed by the same letter do not differ (P>0.05).

Figure 5. Effects of time of year and defoliation strategy on forage mass in palisadegrass swards.

45W-30Sp-30Su: sward kept at 45 cm in winter and 30 cm in spring and summer; 30W-30Sp-30Su: sward kept at 30 cm in winter,

spring and summer; 15W-30Sp-30Su: sward kept at 15 cm in winter and 30 cm in spring and summer. Lowercase letters compare

defoliation strategies within each season of the year, and uppercase letters compare seasons of the year within each defoliation strategy. Means followed by the same letter do not differ (P>0.05).

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

148 M.E.R. Santos, M.G. Simplício, G.P. Silva, H.A. de Oliveira, L.K.P. da Costa and D.O.C. de Sousa

Figure 6. Percentage of live leaf blades in the forage mass of palisadegrass according to season of the year (A) and defoliation management strategy (B).

45W-30Sp-30Su: sward kept at 45 cm in winter and 30 cm in spring and summer; 30W-30Sp-30Su: sward kept at 30 cm in winter,

spring and summer; and 15W-30Sp-30Su: sward kept at 15 cm in winter and 30 cm in spring and summer. In each graph, means

followed by the same letter do not differ (P>0.05).

The percentage of stems (PS) was influenced by

The percentage of dead material was not influenced by

season of the year (P<0.0001), defoliation strategy (P =

season of the year (P = 0.191), defoliation strategy

0.0002) and the interaction of these factors (P = 0.007). In

(P = 0.575) or by the interaction of these factors

winter, the sward kept at 15 cm in fall and winter dis-

(P = 0.305), averaging 23%.

played a lower PS than those kept at 45 and 30 cm. During

Season of the year affected leaf area index (LAI)

spring and summer, PS was independent of the sward

(P<0.0001), with a lower value in winter than in spring

height during the fall/winter period (Figure 7).

and summer (Figure 8).

Figure 7. Percentage of live stems in the forage mass of palisadegrass according to time of year and defoliation strategy.

45W-30Sp-30Su: sward kept at 45 cm in winter and 30 cm in spring and summer; 30W-30Sp-30Su: sward kept at 30 cm in winter,

spring and summer; 15W-30Sp-30Su: sward kept at 15 cm in winter and 30 cm in spring and summer. Lowercase letters compare

defoliation strategies within each season of the year, and uppercase letters compare seasons of the year within each defoliation strategy. Means followed by the same letter do not differ (P>0.05).

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Sward height and yield of palisadegrass 149

The adverse climatic conditions for plant growth in

winter (Figure 1) might also have resulted in a lower

percentage of live leaf in the forage mass in this season as

compared with spring and summer (Figure 6A). Low

temperatures and water deficit, typical of winter conditions,

decrease leaf appearance and elongation rates (Lara and

Pedreira 2011b), which would reduce the percentage of live

leaves in the forage mass. A similar lower percentage of live

leaves during winter was observed by Paula et al. (2012) in

palisadegrass pastures continuously grazed at 15, 30 and 45

cm throughout the year.

The low tiller density in winter (Figure 3) was partially

responsible for the low forage mass in swards maintained

at 15 and 30 cm in fall/winter (Figure 5), as well as for the

lower leaf area index (LAI) in all swards (Figure 8) in

winter. Three structural traits could potentially change the

Figure 8. Leaf area index of palisadegrass according to

sward LAI: tiller density, number of leaves per tiller and

season of the year.

leaf blade size. Of these, tiller density has the greatest

Means followed by the same letter do not differ (P>0.05).

potential to change the LAI (Matthew et al. 2000).

According to Fagundes et al. (2005), the low LAI of the

Discussion

pastures in winter would be a result of the lower number

of live leaves per tiller and the shorter final length of the

This study has provided further valuable information on

leaves at that time.

how the height, at which a marandu palisadegrass pasture

On the other hand, in spring and summer, the increase

is maintained in winter, spring and summer, affects the

in temperature and occurrence of rainfall (Figure 1)

structure and composition of the pasture. This will be of

provided favorable conditions for tillering, resulting in

use in explaining why pastures behave differently and

increased numbers of tillers (Figure 3), a typical response

have different levels of production under differing

pattern observed in other research studies with forage

grazing strategies, especially in winter.

grasses of the genus Brachiaria (Sbrissia and Silva 2008;

We hypothesized that keeping pasture short in winter

Calvano et al. 2011). Lara and Pedreira (2011b) recorded

would allow greater light penetration to the base of the

twice as many tillers in summer as in winter in cvv.

sward, which might stimulate greater tiller development

Marandu, Xaraés, Arapoty and Capiporã of Urochloa

brizantha (syn. Brachiaria brizantha) and cv. Basilisk of

in spring as reported by Matthew et al. (2000) and Sbrissia

U. decumbens (syn. B. decumbens).

et al. (2010). However, the defoliation strategy in

The greater number of tillers in spring and summer

fall/winter did not influence the number of tillers in the

(Figure 3) resulted in a higher LAI of the swards in these

sward in spring and summer, which demonstrates the

seasons (Figure 8). Since increased LAI increases

flexibility of marandu palisadegrass to variations in

interception of light by the sward (Pedreira et al. 2007),

height in the fall and winter. During fall/winter tiller

which is a premise for the occurrence of photosynthesis

density was similar on all pastures regardless of sward

(Taiz and Zeiger 2012), this results in increased growth

height and increased following the onset of better

rate of the pasture.

conditions for growth in spring. Climatic conditions

As a consequence of the accumulated effects of

seemed to be the overriding factor. There was very little

rainfall, temperature and solar radiation as the seasons

precipitation in June and no rain in July and August, with

progressed, a larger number of tillers was expected in

mean minimum temperature below 15 ºC (Figure 1).

summer than in spring. This response pattern did not

When the temperature is below 15 ºC, the lower threshold

occur, possibly due to the lower than normal rainfall

temperature for marandu palisadegrass (Mendonça and

experienced in January and February 2014 (Figure 2).

Rassini 2006), the rate of photosynthesis is impaired,

Additionally, the similar LAI in spring and summer

which compromises tillering in the pasture. Sbrissia and

(Figure 8) might also have contributed to tiller density

Silva (2008), in a study with marandu palisadegrass under

remaining stable in these seasons (Figure 3). The LAI

continuous stocking, also observed lower tiller density in

controls, in part, the amount of solar radiation that reaches

winter than in spring and summer.

the soil surface, such that a larger LAI is associated with

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

150 M.E.R. Santos, M.G. Simplício, G.P. Silva, H.A. de Oliveira, L.K.P. da Costa and D.O.C. de Sousa

higher light interception by the sward (Giacomini et al.

greater stem elongation and consequently a greater tiller

2009) and in fact, with lower penetration of light to the

weight (Figure 4), as well as a higher percentage of live

soil. Since the amount of light received at the base of

stems in the forage mass (Figure 7). This high relative

plants has a significant influence on degree of tillering

contribution of live stem in winter resulted in a reduction

(Martuscello et al. 2009), the constancy of LAI in spring

in the percentage of live leaves during the entire

and summer might have provided similar levels of

experimental period in the sward kept at 45 cm in

luminosity close to the soil surface, resulting in similar

fall/winter as compared with that kept at 15 cm (Figure

numbers of basal buds developing into new tillers. The

6B). Nevertheless, in spring, when all swards were kept

maintenance of marandu palisadegrass at a constant

at the same height (30 cm), the highest one (45 cm) in fall

height in spring and summer also resulted in similar tiller

and winter continued to present a greater tiller weight.

weight in these seasons to the swards managed at 15 and

Thus, a residual effect of the management employed in

45 cm in fall/winter (Figure 4).

fall and winter was detected in the subsequent season.

On swards maintained at 15 and 30 cm in fall/winter,

Contrastingly, maintaining the sward lower (15 cm) in fall

the greater forage mass in summer than in the other

and winter resulted in lower tiller weight in winter (Figure

seasons of the year (Figure 5) might have been a

4), as well as a lower percentage of live stems in the

consequence of the onset of flowering of the palisadegrass

forage mass during winter (Figure 7). These results allow

in this season (Calvano et al. 2011). With flowering, the

us to infer that the structure of the marandu palisadegrass

leaf:stem ratio in the plant is reduced (Santos et al. 2009),

kept shorter in winter would be more favorable for forage

which explains the lower percentage of live leaves in the

intake by grazing animals.

forage mass in summer as compared with spring (Figure

The effect of a particular defoliation strategy in a

6A). Since stem is a denser organ than leaf (Pereira et al.

particular season of the year on tiller growth in the

2010), its greater proportion in the sward should result in

following season is partially due to the phenotypic

a larger forage mass. Furthermore, with flowering,

plasticity of the forage plant, i.e. to the change in the

compounds from root reserves are translocated to the

morphogenetic and structural traits of the plant in

aerial parts of the forage plant (Silva et al. 2015), which

response to environmental variations, including the

also contributes to increasing the sward forage mass.

defoliation environment (Silva and Nascimento Júnior

It should be noted that we might have overestimated

2007). This is a gradual process, and, therefore, does not

the forage mass values (Figure 5) in this study. To obtain

occur in the short term; when the defoliation manage-

this response variable, we multiplied average tiller weight

ment in a sward is changed, there is a carry-over effect

by the number of tillers. It is possible that some young

and effects of the previous management are displayed in

tillers, shorter than the average sward height, were

counted along with the taller ones. However, to determine

the subsequent periods.

mean tiller weight, we harvested only those with height

similar to the sward height, so the average tiller weight

Conclusions

would have been overestimated, with an equal effect on

forage mass.

This study has shown that: 1) Urochloa brizantha (syn.

Considering that the tiller is the basic growth unit of

Brachiaria brizantha) cv. Marandu (marandu palisade-

forage grasses (Hodgson 1990), the stability of tiller

grass) shows limiting structural traits in winter as compared

density in the swards subjected to variable defoliation

with spring and summer; 2) both pasture height and season

regimes in fall and winter indicates that their perenniality

affect pasture structure of Marandu; and 3) managing

was not compromised and that the growth potential of the

Marandu at 15 cm in fall and winter and 30 cm in spring

pasture was probably not impaired.

and summer will result in a leafier pasture with lower

In winter, variations in mean weight of tillers (Figure

percentage stems than keeping it at 30 or 45 cm in winter.

4) and forage mass (Figure 5) were a consequence of the

Grazing studies seem warranted to determine whether

modification of the sward height in this season. When the

the effects demonstrated in this experiment hold under

sward heights were similar (30 cm) in all swards,

grazing and how varying pasture height in different

differences in tiller weight and forage mass between the

seasons compares with maintaining a fixed grazing

swards declined and had disappeared by summer (Figure

height. Furthermore, how the sward height variation

4). Moreover, in the sward kept at 45 cm in fall and

affects pasture yield and quality and translates into animal

winter, there might have been more competition for light

performance should be monitored before recommen-

among the tillers (Sbrissia et al. 2010), which can lead to

dations should be made.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Sward height and yield of palisadegrass 151

Acknowledgments

Köppen W. 1948. Climatologia. Gráfica Panamericana, Buenos

Aires, Argentina.

We thank Fundação de Amparo à Pesquisa do Estado de

Lara MAS; Pedreira CGS. 2011a. Estimativa da assimilação

Minas Gerais for financial support, and the interns of

potencial de carbono em dosséis de espécies de braquiária.

Grupo de Estudo e Pesquisa em Forragicultura of the

Pesquisa Agropecuária Brasileira 46:743‒750. DOI:

Federal University of Uberlândia for their endeavors in

10.1590/s0100-204x2011000700010

Lara MAS; Pedreira CGS. 2011b. Respostas morfogênicas e

conducting the activities of this project.

estruturais de dosséis de espécies de Braquiária à

intensidade de desfolhação. Pesquisa Agropecuária

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(Received for publication 30 September 2016; accepted 11 June 2017; published 30 September 2017)

© 2017

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Tropical Grasslands-Forrajes Tropicales (2017) Vol. 5(3):153–162 153

DOI: 10.17138/TGFT(5)153-162

Research Paper

Evaluation and strategies of tolerance to water stress in Paspalum

germplasm

Evaluación y estrategias de tolerancia a estrés hídrico en germoplasma de

Paspalum

CRISTIANA DE G. PEZZOPANE1, ARTHUR G. LIMA2, PEDRO G. DA CRUZ3, TATIANE BELONI4,

ALESSANDRA P. FÁVERO5 AND PATRÍCIA M. SANTOS5

1 Centro Universitário Central Paulista - UNICEP, São Carlos, SP, Brazil www.unicep.edu.br

2 Universidade Estadual Paulista (UNESP), Rio Claro, SP, Brazil www.unesp.br

3 Embrapa Rondônia, Porto Velho, RO, Brazil www.embrapa.br/rondonia

4 Universidade Federal de São Carlos, Araras, SP, Brazil www.ufscar.br

5 Embrapa Pecuária Sudeste, São Carlos, SP, Brazil www.embrapa.br/pecuaria-sudeste

Abstract

The evaluation of genetic resources in germplasm banks of Paspalum can contribute to their use in breeding programs

and for advanced research in biotechnology. This study evaluated the tolerance of 11 Paspalum accessions to abiotic

stress caused by soil water deficit in a greenhouse experiment at Embrapa Pecuária Sudeste, São Carlos, state of São

Paulo, Brazil. The variables analyzed were: dry biomass of green matter, dead matter and roots; leaf area; leaf water

potential; number of days to lose leaf turgor (wilting); soil moisture at wilting; and number of tillers per pot. The results

showed high genetic variability for all traits, not only among species but also within species, and also reflected the existence of different strategies of response and potential adaptation to water deficit events. For breeding programs, when the aim is to produce materials better adapted to the occurrence of prolonged drought, 5 accessions from this group

seem to have good potential: P. malacophyllum BGP 289, P. quarinii BGP 229, P. regnellii BGP 112, P. conspersum BGP 402 and P. urvillei x P. dilatatum BGP 238. Conversely, when the goal is to select materials for short-term water stress conditions, 6 accessions stand out: P. atratum BGP 308, P. regnellii BGP 215, 248 and 397, P. dilatatum BGP

234 and P. malacophyllum BGP 293.

Keywords : Abiotic stress, genotypes, germplasm bank, water deficit.

Resumen

La evaluación de recursos genéticos en bancos de germoplasma de Paspalum constituye una gran ayuda en programas de

mejoramiento genético y de investigación avanzada en biotecnología. En un experimento en macetas en Embrapa Pecuária

Sudeste, São Carlos, estado de São Paulo, Brasil, se evaluó la tolerancia de 11 accesiones de varias especies de Paspalum

al estrés abiótico causado por el déficit hídrico en el suelo. Las variables analizadas fueron: biomasa seca de la materia

verde, materia muerta y raíces; área foliar; potencial hídrico foliar; número de días hasta la pérdida de la turgencia foliar

(marchitamiento); humedad del suelo al momento del marchitamiento de las plantas; y número de brotes por planta. Los

resultados mostraron tanto una alta variabilidad genética para todos los parámetros, no solo entre las especies, sino también

dentro de las especies, como la existencia de diferentes estrategias de respuesta y potencial adaptación a eventos de déficit

hídrico. Para los programas de fitomejoramiento, cuando el objetivo es producir materiales mejor adaptados a la sequía

___________

Correspondence: P.M. Santos, Embrapa Pecuária Sudeste, Rodovia

Washington Luiz, km 234 s/nº, Fazenda Canchim, São Carlos CEP

13560-970, SP, Brazil.

Email: patricia.santos@embrapa.br

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

154 C.G . Pezzopane, A.G. Lima, P.G. Cruz, T. Beloni, A.P. Fávero and P.M. Santos

prolongada, las accesiones con mayor potencial fueron: P. malacophyllum BGP 289, P. quarinii BGP 229, P. regnellii BGP 112, P. conspersum BGP 402 y P. urvillei x P. dilatatum BGP 238. Por el contrario, cuando el objetivo es seleccionar materiales para condiciones de estrés hídrico de corta duración, se destacan las accesiones: P. atratum BGP 308, P. regnellii BGP 215, 248 y 397, P. dilatatum BGP 234 y P. malacophyllum BGP 293.

Palabras clave : Banco de germoplasma, déficit hídrico, estrés abiótico, genotipos.

Introduction

P. dilatatum, P. plicatulum and P. guenoarum, are used

successfully as forages (Acuña et al. 2011). The number

According to predictions from the fifth assessment report

of accessions and species conserved has been growing in

(AR5) of the Intergovernmental Panel on Climate Change

recent years, and the Germplasm Bank (GB) of Embrapa

(IPCC 2013) global temperature may increase by up to

Pecuária Sudeste contains more than 340 accessions of 49

4.8 °C by 2100, with increased variability and occurrence

different species of Paspalum, most belonging to the

of extreme events. In Brazil, a regionalized projection

informal group Plicatula.

suggests trends for increasing maximum and minimum

Batista and Godoy (2000) evaluated the dry matter

extremes of temperature and high spatial variability for

(DM) production of 217 accessions of Paspalum from the

precipitation when analyzing different emission scenarios

Paspalum GB of Embrapa Pecuária Sudeste, using

(Marengo et al. 2009). The challenges presented by the

B. decumbens and Andropogon gayanus cv. Baetí as

effects of climate change scenarios on agriculture are

controls. While 58 accessions (27%) showed DM

adaptation of production systems and mitigation of

production equal to or higher than the cultivars used as

greenhouse gas emissions.

controls, the selection and development of new cultivars

Plant breeding programs are designed to incorporate

should also take into account the plasticity in the response

relevant traits, such as high dry matter yield, high

of the genotype to specific conditions.

nutritional value and increased resistance to or tolerance

Some species of Paspalum, such as P. vaginatum

of biotic and abiotic factors into elite genetic resources,

(Shahba et al. 2014) and P. notatum (Acuña et al. 2010),

with the aim of releasing cultivars better suited to the

have characteristics of interest in relation to drought

conditions of use. Knowledge of these characteristics in

genotypes conserved in gene banks provides fundamental

tolerance. While some species have high forage value, no

information that allows the selection of appropriate

controlled experiments checking the tolerance to water stress

accessions for use both in breeding programs and in

of species like P. atratum, P. conspersum, P. dilatatum, P.

biotechnology research.

malacophyllum, P. quarinii and P. regnellii have been

The characterization of accessions conserved in

conducted. According to Zuloaga and Morrone (2003), P.

germplasm banks is essential to ensure their efficient use

malacophyllum is found from Mexico to northern Argentina,

for different purposes. For example, the study of

Paraguay, Brazil and Bolivia, at elevations from sea level to

responses of forage plants to stress caused by water deficit

3,000 m. It is found in agricultural fields, roadsides and

is of utmost importance, since moisture restriction can

woodlands. In turn, P. regnellii is distributed from the center

greatly reduce forage production and persistence of

to the south of Brazil, northeastern Argentina and eastern

pasture (Guenni et al. 2002; Melo et al. 2003; Araújo et

Paraguay. Both P. conspersum and P. regnellii are recorded

al. 2012; Volaire et al. 2014).

in forest edges or disturbed sites, in heavy clay soils which

The genus Paspalum belongs to the family Poaceae

are subject to waterlogging. Accession BGP 238 used in this

and includes several grasses with forage potential. More

study is a natural hybrid derived from a cross between

than 330 species have been identified (Zuloaga and

P. urvillei and P. dilatatum. Since P. urvillei has sexual

Morrone 2003), occurring widely in South America

reproductive behavior, it is common to observe hybrids in

(Quarín et al. 1997), including the Pampas, where the

populations where these species coexist.

grass is grazed by cattle, in particular. Nevertheless, its

This study evaluated the tolerance to soil moisture stress

use in cultivated pastures is still low in Brazil, while in

in some germplasm accessions of Paspalum, aiming at

other countries, like the USA, many species of Paspalum

identifying genes for drought-tolerance and transferring

that occur in Brazil, such as Paspalum notatum,

them to other plant families in future breeding programs.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Water stress tolerance in Paspalum 155

Materials and Methods

24 mmolc/dm3, Al 0 mmolc/dm3, CEC 66 mmolc/dm3,

base saturation 63%, sand 417 g/kg, silt 253 g/kg and clay

The experiment was conducted in a greenhouse, at

330 g/kg.

Embrapa Pecuária Sudeste, in São Carlos, state of São

Each pot was fertilized with 1.07 g N as urea, 1.4 g P

Paulo (21°57’ S, 47°50’ W; 860 m asl). We evaluated 11

as simple superphosphate, 0.53 g K as potassium chloride,

accessions of 7 distinct species of Paspalum belonging to

following the recommendations of Malavolta (1980) for

5 different informal groups. Seeds were obtained from the

experiments in pots.

germplasm bank of Embrapa Pecuária Sudeste (Table 1).

The experimental layout was an 11 (accessions) x 2

The accessions were chosen after a previous study

(water conditions) x 3 (replications) factorial in a

identified genotypes more suitable for forage production.

complete randomized block design. The 2 watering

Among these genotypes, 2 belonged to the informal

treatments were unwatered and irrigated regularly. When

botanical group Dilatata (BGP 234, Paspalum dilatatum

the plants had at least 3 tillers, irrigation of pots in the

Poir. biotype Uruguaiana and BGP 238, a natural hybrid

treatment with water stress was suspended, while

between P. urvillei Steud. and P. dilatatum), 2 to the

irrigation of pots in the control treatment continued with

group Malacophylla (BGP 289 and BGP 293, Paspalum

a daily amount of water equivalent to the air evaporative

malacophyllum Trin.), 1 to the group Plicatula (BGP 308,

demand as measured by several Piche evaporimeters

Paspalum atratum Swallen), 1 to the group Quadrifaria

located at random in the greenhouse.

(BGP 229, Paspalum quarinii Mez) and 5 to the group

Plants of particular accessions in the unwatered

Virgata (BGP 402, Paspalum conspersum Schrader and

treatment were harvested when the first leaf blade

BGP 112, 215, 248 and 397, Paspalum regnellii Mez).

displayed wilting in the predawn period, so different

Seedlings were grown on trays filled with organic

accessions

were

collected

on

different

days.

substrate Plantmax® and transplanted to pots at the 3-leaf

Concomitantly, in the same block, we collected a pot with

stage with 2 plants per pot. Pots with capacity of 8.5 L

2 plants of the same accession from the control treatment.

were filled with 7 kg sieved soil, with the following

Therefore, 2 pots were collected on each occasion for

chemical and physical characteristics: pHCaCl2 5.4, OM 25

each accession, 1 from the stressed treatment showing

g/dm3, Presin 6 mg/dm3, SO4-S 21 mg/dm3, K 1.3

symptoms of wilting and another with well-watered

mmolc/dm3, Ca 26 mmolc/dm3, Mg 14 mmolc/dm3, H+Al

plants from the control.

Table 1. Identification codes (BGP and collection), species names, collection sites and informal botanical groups of Paspalum accessions evaluated in this study.

Site code

Collection code

Species

Collection site

Botanical

(BGP)

group

112

VDBdSv 10073

P. regnellii Mez

Praia Grande - Santa Catarina - Brazil

Virgata

215

Lr 2

P. regnellii Mez

Itirapina - São Paulo - Brazil

Virgata

229

VTsDp 14220

P. quarinii Morrone &

São Miguel das Missões - Rio Grande do Sul - Quadrifaria

Zuloaga

Brazil

234

VTsDp 14251

P. dilatatum Poir.

Uruguaiana - Rio Grande do Sul - Brazil

Dilatata

biotipo Uruguaiana

238

VTsZi 14285

P. urvillei x P. dilatatum

Xangri-lá - Rio Grande do Sul - Brazil

Dilatata

248

VTsRcRm

P. regnellii Mez

Capão Alto - Santa Catarina - Brazil

Virgata

14424

289

VRcMmSv

P. malacophyllum Trin.

Aral Moreira - Mato Grosso do Sul - Brazil

Malacophylla

14582

293

VRcMmSv

P. malacophyllum Trin.

Japorã - Mato Grosso do Sul - Brazil

Malacophylla

14606

308

VRcMmSv

P. atratum Swallen

Terenos - Mato Grosso do Sul - Brazil

Plicatula

14525

397

-

P. regnellii Mez

unknown origin

Virgata

402

-

P. conspersum Schrader

unknown origin

Virgata

Collectors: Bd = I.I. Boldrini; D = M. DallÁgnol; Dp = Dario Palmieri; Lr = L.A.R. Batista; Mm = M.D. Moraes; Rc = Regina

Célia de Oliveira; Rm = R. Miz; Sv = Glocimar P. da Silva; Ts = T. Souza-Chies; V = José Francisco M. Valls; Zi = F. Zilio.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

156 C.G . Pezzopane, A.G. Lima, P.G. Cruz, T. Beloni, A.P. Fávero and P.M. Santos

When the plants were harvested, the following

P. regnellii BGP 215, with no significant differences

parameters were measured: leaf water potential (MPa),

among genotypes (P = 0.43).

determined in the last expanded leaf, in the pre-morning

Drying caused significant differences (P<0.0001) in leaf

period, with the aid of a psychrometer (Wescor micro-

water potential values in all accessions (Figure 1E), with no

meter Psypro model and sample chamber model C52),

significant differences among accessions (P = 0.33). In

where a microvoltmeter is connected to chambers where,

contrast, the number of tillers per pot (Figure 1F) was

after being calibrated with NaCl standard solution, 25 mm

affected differently by drying for different genotypes

diameter leaf discs are placed to be measured; green

(P<0.0001). Responses ranged from an increase in the

biomass; dead biomass; and root biomass determined after

number of tillers under water stress conditions of 19% for

each of the parts was packed in paper bags and dried in a

P. quarinii BGP 229 to a decrease of 34% in tiller numbers

circulation oven at 65 °C until reaching constant weight;

for P. malacophyllum BGP 293. There was considerable

total leaf area, measured using the LI-COR leaf area

variation among accessions in time to wilting following the

integrator, model LI-3100; days to turgor loss (wilting);

cessation of watering, with a range from 9 days for

soil moisture at wilting determined by weighing wet soil

P. regnellii BGP 215 to 22 days for P. malacophyllum BGP

and then drying to constant oven weight at 105 °C; and

289 (Figure 1G) (P<0.0001). However, most accessions

number of tillers per pot.

wilted between 17 and 22 days after watering ceased. At the

At the completion of the harvests, data were analyzed

point of wilting for all accessions, soil moisture levels were

using the PAST software (Hammer et al. 2001), using

about 12% (Figure 1H).

principal component analysis. This analysis is based on

Principal Component Analysis (PCA) was performed

grouping assessments to determine the genetic differences

to group accessions according to the variables that had

(Cruz 2006).

most influence on their responses. Figure 2A illustrates

the PCA comparing the accessions under both drought

Results

and well-watered conditions, and considering all the

variables recorded in this study. The cumulative variance

There were no significant interactions among genotypes

of the first 2 components was 73.9%. The x-axis was

and watering treatments for any of the variables. There

characterized by leaf area and the y-axis by the number of

was an increase (P<0.0001) in dry biomass of dead

tillers. Two distinct groups were formed, one consisting

material of shoots (Figure 1A) in all studied accessions

of accessions under water restriction (to the left) and the

under water restriction, especially for P. regnellii BGP

other composed of non-stressed accessions (to the right),

215, which showed 62% more dead material than the

indicating differences between the groups; water

control. There was no significant difference among

restriction was critical in changing

the main

genotypes (P = 0.09).

characteristics of plants.

Despite the lack of significant differences in green

The principal component analysis run only with

biomass between accessions (P = 0.066), there was wide

accessions under water stress, indicated that the variables

variation among accessions in response to drying

that explained best the distribution of genotypes were soil

(P<0.0001). Dry biomass of green matter of accessions

moisture on the x-axis, and dry biomass of roots on the y-

P. malacophyllum BGP 293 and P. regnellii BGP 248 was

axis (Figure 2B). The cumulative variance for the 2 axes

reduced by only 7 and 8%, respectively, as a result of

was 68.4%. In Figure 2B, accessions were grouped

moisture stress, while accessions P. regnellii BGP 215 and

BGP 112 showed decreases of 36 and 40% (Figure 1B).

according to certain characteristics in main number of

Root biomass varied among accessions (P = 0.0004) as

tillers, wilting days, leaf area, water potential and soil

did responses to drying (Figure 1C). Under irrigated

moisture. Accession P. regnellii BGP 215 stood out among

conditions, accessions P. urvillei x P. dilatatum BGP 238

other accessions by the higher dry biomass of roots,

and P. conspersum BGP 402 produced the highest root

P. malacophyllum BGP 293 by the larger leaf area,

yields, while P. malacophyllum BGP 289 and BGP 283

P. regnellii BGP 248 by the higher dry biomass of green

produced the lowest. Drying out under moisture stress

matter and soil moisture and accession P. urvillei x

produced quite variable responses in root biomass, with a

P. dilatatum BGP 238 by dry biomass of dead matter and

range from an increase of 34% in root biomass for

roots. The variable water potential grouped the accessions

P. regnellii BGP 215 to a decrease of 42% for accession

P. dilatatum BGP 234, P. regnellii BGP 397 and

P. conspersum BGP 402 . For this variable, there was no

P. atratum BGP 308, while number of tillers and days to

significant difference among treatments (P = 0.3099).

wilting determined the group formed by P. malacophyllum

Moisture stress caused a reduction (P<0.0001) in leaf

BGP 289, P. quarinii BGP 229, P. conspersum BGP 402

area (Figure 1D) in all accessions, reaching 85% in

and P. regnellii BGP 112.

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Water stress tolerance in Paspalum 157

Figure 1. Mean values of the measured variables for the Paspalum accessions used in this study. Black bars indicate non-stressed plants and grey bars indicate plants under water stress. A. Dead biomass (g DM/pot); B. Green biomass (g DM/pot); C. Root biomass (g DM/pot); D. Leaf area (cm2); E. Leaf water potential (MPa); F. Number of tillers; G. Days to wilting; H. Soil moisture at wilting (%).

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

158 C.G . Pezzopane, A.G. Lima, P.G. Cruz, T. Beloni, A.P. Fávero and P.M. Santos

Figure 2. A – Principal component analysis of accessions of Paspalum subjected (represented by letter D) or not (represented by letter T) to water stress. B ‒ Principal component analysis with only accessions of Paspalum subjected to water stress. Analyses were made considering all variables evaluated (dry biomass of: dead matter - DBDM, green matter - DBGM and roots - DBR; leaf

area; leaf water potential; number of tillers; soil moisture at wilting; and days to wilting).

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Water stress tolerance in Paspalum 159

Discussion

water deficit demonstrated a greater allocation of

photoassimilates to the root system enabling the

This study has provided interesting data on the

exploitation of a larger volume of soil for water

comparative tolerances of a range of Paspalum accessions

absorption, maintaining hydration levels in the tissue for

to low soil moisture situations. As such it provides

longer (Baruch 1994; Casola et al. 1998). The results of

indications of which accessions might be appropriate for

biomass partitioning showed that some accessions

inclusion in breeding programs with specific aims.

invested in root biomass to a greater extent than others.

However, more real differences between accessions

The decrease in leaf water potential with decreasing soil

might exist than appear from our results. The number of

moisture (Figure 1E) was observed previously by Mattos

significant differences obtained between accessions may

et al. (2005) in Urochloa species, where the leaf water

have been limited by the low numbers of plants examined

potential reduced by a factor of 8 in U. mutica and by a

for each treatment combination as large differences in

factor of 4 in the other species studied, U. humidicola,

treatment means in some cases proved to be non-

U. decumbens and U. brizantha. The reduction in leaf

significant (P>0.05). If larger numbers of plants had been

water potential is the consequence of losing water from

included per treatment, more differences might have been

stomata, which is not compensated for by water extraction

recorded as significant.

from the soil. Osmotic adjustment is considered as a

physiological mechanism to maintain turgor at low leaf

Mechanisms of tolerance to stress by water deficit in

water potentials. The decrease in the osmotic potential, due

Paspalum

to the accumulation of sugars, organic acids and ions in the

cytosol, allows the plant to continue to absorb and

Physiological responses of plants to drought conditions

translocate water to the shoot under conditions of lower

are considered primary characteristics because they are

water availability (Bray 1997).

rapidly triggered in the presence of stress (Sherrard et al.

In this experiment, the effect of water restriction on

2009). According to Garcez Neto and Gobbi (2013), all

number of tillers varied according to genotype (Figure

effects caused by water stress lead to production loss and

1F). This result suggests a variation among Paspalum

possible adjustments should be achieved for ecological

genotypes in relation to the capacity to protect

sustainability and productivity of forage grasses grown

meristematic tissues from dehydration during periods of

in environments with eventual or permanent water

water restriction. The reduction in the number of tillers is

restrictions.

related to lower activity of cell division in the

The increase in dry biomass of dead matter in

meristematic zone, responsible for leaf initiation (Skinner

unwatered treatments was not surprising as death of plant

and Nelson 1995), which also influences the activation of

parts as a result of moisture stress is well recognized

axillary buds in the formation of new tillers, prioritizing

(Figure 1A, 1B and 1D). Mattos et al. (2005) studied 4

existing tillers (Garcez Neto and Gobbi 2013).

species of Urochloa subjected to low water availability

The ability of accessions P. quarinii BGP 229,

and observed a decrease in leaf elongation rate and

P. regnellii BGP 112, P. urvillei x P. dilatatum BGP 238

increased senescence of leaf blades for all species.

and P. malacophyllum BGP 289 to delay dehydration

Some species lose leaves as drought is intensified,

longer than others would have been partially due to the

which is known as an avoidance mechanism. This

reduction in leaf area and water potential, which would

strategy allows water savings, because the smaller leaf

have led to energy savings.

area reduces transpiration of water by the plant, favoring

the maintenance of turgor, plus some photosynthetic