Recent advances in the development of salinity and waterlogging tolerant bread wheats

Although there has been a great deal of work on the development of salt-tolerant wheat over the years, there has been little success in carrying the advances in understanding the mechanisms of salt tolerance through to improved yields for poor farmers in saline lands. This may be due to neglect of the interactions between salinity and waterlogging where such stresses occur to : ether, a common occurrence in Pakistan and northern India.Use of the relationship between leaf production and senescence is evaluated as a technique for the simultaneous screening of wheat for salinity and waterlogging tolerance, and found unsuitable. However, the inverse relationship between the numbers of live and of dead leaves allowed the identification of genotypes with higher than expected leaf production, which would be likely to have better aerenchyma production, as well as good root growth. Two genotypes (V 95022 and V 94195) were identified with all these traits, and one (SARC 4) with the leaf traits, and these are being crossed with existing tolerant genotypes to provide improved material. The development of early maturing genotypes of the salt-tolerant but late maturing genotype KTDH 19 through induced mutation is described: of three improved lines showing early maturity and high yield at 150 mol m(-3) NaCl one is also awned. We identify a possible linkage between early maturity and high sodium and chloride uptake and low yields under saline conditions in a mapping population of Chinese Spring X SQ1, a low ABA line. This is a potentially serious constraint on the development of new salt-tolerant wheat for India, Pakistan and other regions where temperatures rise sharply before harvest, although further work will be needed to see if the linkage exists in other genotypes.