Genotypic variation for cellular thermotolerance in Aegilops tauschii Coss., the D genome progenitor of wheat

Heat stress is a major productivity lowering factor in wheat. Wild progenitor species offer a wide spectrum of adaptation traits and can serve as valuable donors of stress tolerance. In the present study, genetic variation in 129 accessions of Aegilops tauschii Coss., the D genome donor of wheat, was evaluated for two heat tolerance related traits viz., cell membrane stability (CMS) and TTC (2,3,5-Triphenyl tetrazolium chloride) based cell viability. Cell membrane stability in the Ae. tauschii accessions at vegetative stage ranged from 15.24 to 80.39%. Nineteen Ae. tauschii accessions were superior to the tolerant bread wheat control (C 273). At anthesis stage a similar spectrum of variation was observed with twenty three accessions showing higher cell membrane stability than C 273. The average CMS level of entire germplasm set at anthesis (47.61%) was lower than at vegetative stage (58.89%). Clear genotypic differences were also observed for TTC based cell viability test. Ae. tauschii accessions displayed a range from 18.73 to 84.39% with eight genotypes excelling over tolerant bread wheat. Correlation of CMS values recorded at two stages was significant but of low predictive value (r(2) = 0.137). Similarly significant but moderate correlation was obtained between CMS and TTC test (r(2) = 0.325). Consequently all the three parameters were used to derive a cell thermotolerance index which was in turn used to identify ten tolerant Ae. tauschii genotypes. The identified accessions were re- evaluated for 1 more year and the three parameters viz., CMS at vegetative (r(2) = 0.954) and anthesis stage (r(2) = 0.932) and TTC cell viability at vegetative stage (r(2) = 0.888) showed high correlation Strategy for use of identified accessions as donors is discussed.