Brachiaria hybrids : potential , forage use and seed yield

A brachiaria breeding program initiated in 1988 at CIAT (Centro Internacional de Agricultura Tropical, Cali, Colombia) combined desirable attributes found in accessions of Brachiaria brizantha and B. decumbens. Three apomictic hybrids have been released (cvv. Mulato, Mulato II and Cayman). Mulato showed agronomic potential but seed yields were low. Trials in Central America demonstrated the superiority of Mulato II, a vigorous grass with deep and branched roots, giving it excellent drought tolerance in the Brazilian Cerrado and Mexico, plus outstanding nutritional value. Following trials in Mexico and Thailand, evaluating 155 new hybrids for 7 years, cv. Cayman was released due to strong waterlogging tolerance. Research on production, quality and seed yields of brachiaria hybrids in Asia, the Americas and Africa from 2003 to 2013 is summarized in this paper.


Introduction
The registration of Mulato hybrid brachiaria (Brachiaria ruziziensis x B. brizantha) by Grupo Papalotla in 2004 (Miles et al. 2004) and the granting of Plant Variety Rights (PVR) in 2002, marked a significant breakthrough for tropical perennial forage cultivars.Until 2001, Brachiaria spp.cultivars used commercially were derived without genetic modification directly from natural germplasm collected in Africa or selected fromgermplasm collections in Australia and tropical America.The development in Belgium of a tetra-__________ Correspondence: Esteban A. Pizarro, Grupo Papalotla, Semillas Papalotla SA de CV., Orizaba #195,Col. Roma,C.P. 06700,México D.F.,Mexico. Email: eapizarro@gmail.comploidized sexual ruzi grass (B.ruziziensis) (Swenne et al. 1981) and further studies by Ndikumana (1985) and Valle et al. (1994), led to Embrapa (Empresa Brasileira de Pesquisa Agropecuária) providing tetraploid, sexual ruzi grass to CIAT in 1988.The breeding program at CIAT combined desirable attributes found in accessions of B. brizantha and B. decumbens.
In 2001, Grupo Papalotla, a Mexican seed company, was granted the exclusive rights worldwide, to produce, research and commercialize the first generation of brachiaria hybrids developed by CIAT from 2001 to 2010.Mulato showed considerable agronomic potential but seed yields were low (Hare et al. 2007a).Fortunately, trials in tropical America found Mulato II had excellent drought tolerance in the Brazilian Cerrado and Mexico and its seed yields in Thailand were between 60 and 100% higher than the highest seed yields of Mulato (Hare et al. 2007b;2007c) This paper summarizes research on production, quality and seed yields of brachiaria hybrids in Asia, the Americas and Africa from 2003 to 2013.

Asia
Field studies at Ubon Ratchathani University, Thailand (15 N), between 2003 and 2007, showed that Toledo palisade grass (Brachiaria brizantha), Mulato and Mulato II produced more total DM and leaf DM, particu-larly during the dry season, than other brachiaria grasses (Hare et al. 2009), Mulato II also producing significantly more leaf than Toledo palisade grass and Mulato.It is the production of green leaves that makes Mulato II a particularly attractive forage for livestock (Mutimura and Everson 2012).
Further trials conducted in Thailand by DLD showed that leaf DM digestibility of Mulato II and 3 hybrid brachiaria lines averaged 75% and stem DM digestibility averaged 60%.
Research during 2005−2007 at the Tropical Pasture Research Center, Chinese Academy of Tropical Agricultural Sciences (CATAS) in Hainan, China (19 N), on acid soils (pH 4.9−5.5),with annual rainfall of 1600 mm, found that Mulato and B. brizantha cv.Reyan 6 produced significantly more DM than Mulato II, B. decumbens and B. humidicola, even though Mulato II had a higher leaf:stem ratio.In Guangxi, China (25 N), Mulato II was found to be very susceptible to winter cold, with only 5% plant survival in May, following 2 days below 0 C in December.This was similar to results from Florida, USA, where Mulato II pastures are considerably weakened by winter temperatures below 0 C and recover slowly in spring (Vendramini et al. 2012).

The Americas
Seed production trials were conducted at Warnes, Bolivia (19 S; 423 m asl), from 2007 to 2010 on hybrid brachiaria lines BRO5, MXO2 and BRO4.Over 4 years, only 1 new line, MXO2/2552, produced more seed than Mulato II, due to a high seed yield in 2010.In 2009, seed yields were low overall, due to dry conditions during anthesis and seed set.Further trials from 2008 to 2010 at the same location, found that none of the BRO6 lines produced significantly more seed than Mulato II.
In Mexico, evaluations on the hybrid brachiaria collections commenced in 2005 at Santa Elena, Oaxaca (16 N; 4−8 m asl; 800−1200 mm annual rainfall; 6−8 months dry season) on very sandy soils, with low organic matter, N and P and a pH of 5.6.To date, studies have been conducted on 15 BRO2 lines, 38 BRO5 lines, 28 BRO6 lines and 74 BRO9 lines.
Within the BRO2 lines, 4 lines (1718, 0465, 1752 and 1794) were selected from the Mexico and Thailand studies and granted PVR.Further trials with BRO2/1752 showed that it displayed superior waterlogging tolerance compared with Mulato II and 38 BRO6 lines.It was subsequently released as cultivar Cayman.
In the USA, forage production and nutritive value of Mulato II and Cayman under grazing were studied at the University of Florida, Beef Research Unit (29 N; 45 m asl) from 2010 to 2011 (João Vendramini pers.comm.).Under intensive grazing every 2 weeks, both hybrids had significantly higher percentage of leaf (70−80%), crude protein (19−21% in leaves, 10−12% in stems) and in vitro organic matter digestibility (73−75% leaf, 59−61% stem) than under grazing every 4 and 6 weeks, similar to the high quality achieved under cutting in Thailand.

Africa
Improved hybrid brachiaria grasses were evaluated in Rwanda (2 S) at a lower rainfall site (1400 mm/year) and a higher rainfall site (1800 mm/year) that had high soil Al levels (47 meq/100g of soil), against local signal grass (B.decumbens) and a naturalized buffel grass (Cenchrus ciliaris).At the lower rainfall site, BRO2/1485 and the local signal grass produced more DM than buffel grass and the brachiaria hybrids BRO2/0465 and BRO2/1452.When asked to rank the grasses, farmers selected Mulato II as the preferred cultivar at both sites, because of its year-round production of green forage without any input of fertilizer, high DM production, palatability, drought tolerance, quick regrowth, persistence, perenniality, and being easy to cut and carry (Mutimura and Everson 2012).

Commercial pasture development
In Vietnam, Mulato II is used as cut-and-carry forage by dairy farmers because of its high protein levels, palatability and digestibility (Raf Somers pers.comm.).In Thailand, Laos and Malaysia, expansion of planting of Mulato II has been slow, due to the strong competition from far cheaper ruzi grass seed produced in Thailand.
In the Pacific region, since 2007 over 10,000 hectares of Mulato II pastures have been established in Vanuatu, where it is primarily used for beef cattle grazing.In Africa, Mulato II pastures have been established on nearly 1000 smallholder farms in Kenya, Tanzania and Ethiopia and on larger farms in Congo and Uganda.In Rwanda, 50 hectares of Mulato II have been planted to provide vegetative planting material for famers.In Burundi, Mulato II is currently being evaluated on research stations.
In the Americas, nearly 200,000 hectares of Mulato II pastures have been established since 2005 for both dairy and beef cattle grazing.

Commercial seed production
Mulato II and Cayman seed produced in Thailand and Laos is harvested by hand.In Thailand, the seed is ground-swept and in Laos it is harvested by knocking the seed from seedheads.The seed is hand-cleaned by the farmers and then acid-scarified in Thailand to reach 98% purity, 90% viability and 80% germination.
In tropical America, seed is produced only in Mexico (Mulato II and Cayman) and Brazil (Mulato II), with all seed being ground-swept using machinery (Pizarro et al. 2010).The seeds are cleaned and acid-scarified at a central location in each country.

Conclusion
In many trials in Asia, Africa and the Americas, the hybrid brachiaria cultivars have consistently produced significantly more dry-season forage than other tropical grasses and other brachiaria grasses.Because of its excellent drought tolerance, year-round production of green forage, leafiness, high digestibility and higher crude protein levels than most other tropical grasses, cv.Mulato II is a valuable grass for improved beef and dairy production.Cultivar Cayman also exhibits many of the qualities of Mulato II, and its outstanding waterlogging tolerance adds a new dimension to the hybrid brachiaria collection.Research is now continuing to evaluate the new BRO9 collection to select lines with high seed yields and high forage quality, as well as persistence and tolerance to grazing, or outstanding drought tolerance, or upright form with high DM yields for cut-and-carry forage systems, or good shade tolerance.
. From 2003 to 2008, further detailed studies were conducted in Mexico and Thailand on 155 new hybrid brachiaria lines resulting in 4 lines, BRO2/1718, BRO2/1752, BRO2/1794 and BRO2/0465 being granted PVR.BRO2/1752 produced similar dry matter (DM) yields to Mulato II, and in trials in Mexico demonstrated good waterlogging tolerance.

Table 1 .
Average wet season (May−October) and dry season (November−April) dry matter yields, leaf percentage and pure seed yields of hybrid brachiaria lines from 2005 to 2008 in Ubon Ratchathani, Thailand. www.tropicalgrasslands.info