BRS Mandobi: a new forage peanut cultivar propagated by seeds for the tropics

Forage peanut (Arachis pintoi) is a forage legume of relatively recent use in beef and dairy cattle feeding. Although it is native exclusively to Brazil, the first cultivar, Amarillo, was released in Australia in 1987. Forage peanut has a great number of favorable attributes for establishing grass-legume mixtures, which guarantee the persistence and high yields of high quality forage in cultivated pastures. Therefore, studies with this species have intensified in many tropical regions of the world (Assis and Valentim 2009). In the state of Acre, western Brazilian Amazon, 137,000 ha are cultivated with forage peanut, cv. Belmonte, benefiting thousands of producers, with an annual economic impact of USD 46M (Embrapa 2012). Social and environmental impacts resulting from the use of this legume are also highly positive. However, despite the success achieved in mixed pastures with forage peanut, expansion of the area sown has been relatively slow because vegetative propagation using stolons is labor-intensive and requires large quantities of limited vegetative material. In Brazil, Embrapa has coordinated the development of new forage peanut cultivars and their evaluation in different biomes. The objective of this work is to present a new cultivar of forage peanut propagated by seeds, developed by Embrapa for use in tropical regions, in partnership with Unipasto (Association for Promotion of Forage Breeding Research).


Introduction
Forage peanut (Arachis pintoi) is a forage legume of relatively recent use in beef and dairy cattle feeding. Although it is native exclusively to Brazil, the first cultivar, Amarillo, was released in Australia in 1987. Forage peanut has a great number of favourable attributes for establishing grass-legume mixtures, which guarantee the persistence and high yields of high quality forage in cultivated pastures. Therefore, studies with this species have intensified in many tropical regions of the world ). In the state of Acre, western Brazilian Amazon, 137,000 ha are cultivated with forage peanut, cv. Belmonte, benefiting thousands of producers, with annual economic impact of USD $46 M (Embrapa 2012). Social and environmental impacts resulting from the use of this legume are also highly positive. However, despite the success achieved in mixed pastures with forage peanut, expansion of the area sown has been relatively slow because vegetative propagation using stolons is labour intensive and requires large quantities of limited vegetative material. In Brazil, Embrapa has co-ordinated the development of new forage peanut cultivars and their evaluation in different biomes.
The objective of this paper is to present a new cultivar of seed propagated forage peanut, developed for use in tropical regions, by Embrapa in partnership with Unipasto (Association for Promotion of Breeding Research in Tropical Forage).

Methods
The Brazilian Forage Peanut Evaluation Network started in 1999 and included experiments in the states of Acre, Bahia and Distrito Federal. Development of the new cultivar was based on mass selection over 5 years, followed by evaluation of environmental adaptation in pure stands and in mixed pastures in the western Brazilian Amazon. During the evaluation process, selection was performed to improve speed of establishment, dry matter yield, nutritive value and seed production. Evaluations also occurred under rotational grazing in mixed pastures with Cynodon nlemfuensis, Brachiaria brizantha and B. humidicola, in intensive systems. The new cultivar was registered with the Ministry of Agriculture, Livestock and Food Supply of Brazil in 2008 and its protection process was finalised in 2011, after conducting tests for distinctness, homogeneity and stability. While developing the cultivar, the semi-mechanised seed production system of forage peanut was also established ).

Results and discussion
The new forage peanut cultivar, named BRS Mandobi, presents long and wide leaflets, with high intensity of bristles on the abaxial face of basal leaflets. The basal leaflet apex is acute, whereas the predominant form of the apical leaflet apex is obtuse and its format is obovate. Flowers are yellow and the hypanthium is long. Mandobi presents large stipules in its free portion, not welded to the petiole. Its fruits are also large, compared with cvv. Amarillo and Alqueire 1 .
Mandobi is adapted to tropical and equatorial regions over a rainfall range of 1,200 to 3,500 mm/year. It has high vigour, good leaf:stem ratio and a high degree of tolerance to soil waterlogging. The new cultivar shows good establishment, high dry matter yield and high seed yield (Table 1). It is estimated that in one kilogram there are 6,500 seeds. In the environmental conditions of Acre, a mixed pasture with marandugrass (B. brizantha cv. Marandu), Pueraria phaseoloides and Mandobi reached an annual carrying capacity of 2.5 AU/ha without irrigation or nitrogen fertilisation. Mandobi has persisted for more than 10 years in mixed pastures with Cynodon nlemfuensis, Brachiaria brizantha and Brachiaria humidicola under intensive rotational grazing. Its use in regions with prolonged drought (above 4 months) is the subject of further research.
In Brazil, Amarillo is the only cultivar whose seeds are available in the market, imported from Bolivia and Peru. Amarillo seeds are sold at a very high price, which prevents wide adoption of forage peanut in mixed pastures (Embrapa 2012). In January 2013, the price was around USD $45/kg. Moreover, the cost of local production of Mandobi seeds, based on the production system developed by Embrapa, was around USD $8/kg in 2011  showing that national production of seeds using appropriate technologies can significantly reduce the price of seed, enabling its wider adoption by producers.

Conclusion
The development of cv. Mandobi, combined with an efficient seed production and distribution system, should increase the supply of forage peanut seeds at reduced cost. This presents a new option for producers wishing to introduce a persistent, high-yielding forage legume of high quality into their production systems in the tropics by planting seeds. Mandobi is also an excellent option for recovery of degraded pastures in the Amazon, especially in regions with impermeable soils, where marandu grass is dying.