Breeding for better brassicas: A review

To stablize the yield, it is essential to breed the varieties of rapeseed-mustard having resistance to biotic and abiotic stresses. The breeding problems in the improvement of oil brassicas fall into three categories viz., production breeding, resistance breeding and breeding for special agronomic requirements. A population of allogamous plants exhibits continuous variations. In this it differs from that of autogamous plants which exhibits discontinuous type of variation. Thus, two types of situations can exist, the plants although highly cross pollinated could effect a certain degree as selfing or the plants could be obligatory cross pollination where selfing is excluded. Both types of situations exist in the brassica. Yellow sarson and rai are self compatible while toria and brown sarson are self incompatible. In the former case, depending on the degree of selfing; the population finds itself in a certain equillibrium with reference to the frequency of homozygous and heterozygotes. In these cases selection offers good scope for obtaining types which are constants with regard to a large number of characters. Breeder can alter the pattern of variations bringing the plus variations to the fore discarding the minus ones. There are several approaches that are being utilized in developing commercial hybrids, such as genetic male sterility cytoplasmic male sterility and self incompatibility. The availability of transgenic plants with male sterility and fertility restoration gene facilitated that production of hybrid seed without manual emasculation and controlled pollinations. Genetic engineering for salinity tolerance in brassica has also been takenup.