Molecular Characterization of Bread Wheat (Triticum Aestivum L.) Genotypes Under Salinity Stress Using Ssr Markers

Abstract

Thesis title: "Molecular Characterization of Bread Wheat (Triticum aestivum L.) Genotypes under Salinity Stress using SSR Markers" Globally, wheat (Triticum aestivum L.) is the most important cereal crop. It contributes to 21 % of the food calories and 20 % of protei.n to more than 4.5 billion people in developing countries. Wheat is one of the world's most important food grains which provide staple food for over 40 countries, accounting for 35 percent of the world's population. The world population is increasing rapidly and may reach 6 to 9.3 billion by the year 2050, whereas the crop production is decreasing rapidly because of the negative impact of various environment.al stresses; therefore, it is now very important to develop stress tolerant varieties to cope with upcoming problem of food security. Among stresses, abiotic stress is the principle cause of decreasing the average yield of major crops by more than 50% which cause losses worth hundreds of million dollars each year. Among the abiotic stresses, high salinity stress is the most severe environmental stress, impairing crop production on at least 20% of irrigated land worldwide. In addition, the increased salinity of arable land is expected to have devastating global effects, resulting in up to 50% land loss by the middle of the twenty-first century. The amount of salt affected land is already more than 9 x I 09 ha, which is threat to agriculture. Present study was carried out to evaluate thirty wheat genotypes under control and two salinity stress levels, saline water (ECiw=IO.O dSm"1 ) imposed at 21 days after sowing (Sl) and saline water (ECiw=IO.O dSm"1 ) imposed at the time of sowing (S2). Present study revealed that sufficient genetic variation for salt tolerance existed in selected wheat genotypes tested. The genotypes responded differently to the different salinity levels. Cluster analysis based on ward minimum variance, twelve genotypes K.harchia65, KRLI-4, KRL19, KRL210, KRL213, VL802, AKA W4627, K9423 and HS490 were found most tolerant among genotypes studied. These tolerant genotypes therefore, could be used as a new source of salinity tolerance in wheat breeding programme. In this study selected 24 cultivars were subjected to SSR analysis, we found four SSR markers among the SSR markers used those belong to A, B and D genome significantly correlated with morpho-physiological and biochemical trait. Out of four, two SSR markers, Xgwm135-land Xgwm249-2, were found highly regressed with K:Na. Therefore, could be used as a new marker for association and mapping of salinity tolerant genes. These SSR markers can therefore, be used to ev luate wheat genotypes for salinity tolerance.