Evolution of Grain Legumes. VI. The Future – the Exploitation of Evolutionary Knowledge

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Abstract
SUMMARY: The future evolutionary potential of pulses is determined by the nature and extent of the genetic variability in the primary gene pool. This is extensive in the major grain legumes, notably the groundnut, soyabean, Phaseolus and faba beans, and in the cowpea. It is less extensive in the cultivated lupins and this appears to be a serious limitation to their development as useful crops. The considerable development of isolating mechanisms between related species of legumes has restricted the development of the secondary gene pool. This is most developed in the genus Arachis, where section Arachis provides an extensive secondary gene pool for the groundnut. Tertiary gene pools are potentially quite extensive for many grain legumes but since most interspecific hybrids are inviable this resource would be difficult to exploit with present techniques. The development of sophisticated gene transfer techniques for grain legumes is inhibited by their lack of amenability to in vitro culture. The suggestion is made that genetic resources profiles could be constructed on the basis of an expansion of Harlan and de Wet's gene pool system. These could serve as a guide to the present state of germplasm collections, indicating their strengths and weaknesses, which would be useful in formulating future collection and evaluation strategies.The potential for more intensive exploitation of such legumes as the winged bean and lupins undoubtedly exists. The reasons for past under-exploitation of the winged bean need to be determined.Grain legumes have an assured future for good economic and nutritional reasons. More attention probably should be devoted to exploiting the legume-Rhizobium symbiosis, fundamental to the development of efficient and economic farming systems in the developing world.