Genetic Transformation

Abstract

The large-seeded legume crops, including the common bean (Phaseolus vulgaris L.), are second to cereals with regard to their role in human and animal nutrition, and they are a cheap source of dietary protein, calories, fiber, vitamins, and minerals. This nutritional value is particularly important for the poorer parts of populations in developing countries in Africa, Asia, and Latin America. In the common bean, conventional breeding methods have achieved remarkable progress using sexual recombination (including successful wide crosses, Mejia-Jimenez et al., 1994). However, the lack of genetic variation for certain resistance traits and the difficulties with further interspecific hybridizations, especially with species in the quaternary gene pools and beyond (see Chapter 2 by Debouck), still make breeding a rather slow process, even when marker-assisted breeding is being used (as discussed in Chapter 4 by Kelly & Miklas). In the past, plant geneticists tried to make use of radiation- or chemically-induced mutations, but the respective low frequencies and occurrence of many recessive and loss-of-function mutations failed to convince breeders of the value of these techniques. In addition, in the era of mutation breeding, major emphasis was on yield-related parameters and not on resistance to biotic and abiotic production constraints.