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)
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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Journal of Crop Science 7:1571–1581. https://goo.gl/c2iVJX
(Received for publication 25 August 2016; accepted 3 June 2017; published 30 September 2017)
© 2017
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Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
Tropical Grasslands-Forrajes Tropicales (2017) Vol. 5(3):143–152 143
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 (ISSN: 2346-3775)
Tropical Grasslands-Forrajes Tropicales (2017) Vol. 5(3):153–162 153
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