Breeding Progress and Future Challenges: Abiotic Stresses

Abstract

Mungbean is a short-season tropical grain legume grown on some six million hectares each year. Though predominantly a crop of smallholder farmers and subsistence agriculture mungbean is increasingly seen as a high value crop for international markets with broad acre production under modern farming systems established in Australia, South America, West Asia and Africa. Key benefits of mungbean are its nutritional and monetary value. It provides a short duration, flexible disease break when fit into intensive wheat, rice and summer cereal rotations and its self-sufficiency for nitrogen. The short growing season of 55–100 days places a ceiling on productivity which is further impacted by the traditional low-input farming systems where mungbean is most frequently produced; global yield averages are 0.5 tonnes per hectare though 3 tonnes per hectare is considered achievable under favourable conditions. Increased reliability of mungbean in subsistence systems has been achieved by developing shorter duration, more determinate ideotypes and by the manipulation of sowing time. The strategy of reducing exposure to risk was very successful in transforming mungbean rather than identifying and breeding inherent resilience. The major abiotic stresses of mungbean presented here are drought, heat, waterlogging, low temperatures and salinity. Sources of tolerance identified for all of these stresses have been identified in the germplasm collections of cultivated mungbean as well as wild relatives. Future research efforts must combine known sources of genetic variation with the investigation into the biochemical and physiological processes in order to understand and breed for tolerance to abiotic stress in mungbean.