Mutation breeding by gama irradiation for improvement of assimilate remobilization and production in wheat

Under drought stress condition as one of the most important limiting factor of seed yield in wheat at arid and semi arid regions, the remobilization of assimilates gain more value for filling the grains. The mutant genetic materials are invaluable tools to understand the physiology of remobilization and to help the introducing new drought tolerant cultivars. The aim of this study was to determine the reasons of variation in bread wheat genotypes in the process of remobilization and its relationship with grain yield in drought stress conditions and the role of mutation breeding in bread wheat breeding programs under drought stress.
Two advanced mutant lines of bread wheat (T-67-60 and T-65-7-1) having improved remobilization along with the wild type (cv. Tabasi) were planted at two moisture conditions (normal and 30-40% of field capacity) as a factorial experiment based on a completely randomized design with three replications. Drought treatment initiated at full heading stage (Zadoks 60) and for measuring remobilization and other related parameters, sampling from internodes of the main stem was conducted over 5 times at intervals of 7 days (0, 7, 14, 21, 28 days after anthesis).
Based on the results the capacity of genotypes to storage assimilates before terminal stress and high capability of the sink are main factors to determine the amounts of stem remobilization. Considering the senescence possibly induced by drought stress on the mutant lines (as a stimulating factor for remobilization), yield and maximum specific weight, remobilization and remobilization efficiency of the lines were in better situation than the wild type (cv. Tabasi). Also the using the full-length potential of stem had a key role in the mobilization of stem reserves. For better response to stress conditions, mutant line T-65-7-1 has utilized from potential of all parts of the stem (peduncle, penultimate and lower Internodes) for remobilization of assimilates.
Based on the results we can say that the reasons of variation in bread wheat genotypes in the process of remobilization are the difference in receiving signals of senescence phenomenon under drought stress, capability of the sink, the rate of the reserves assimilated before anthesis and the use of reserves capacity over stem (different stem internodes).