study of genetic variation on response to spring cold stress in iranian bread wheat cultivars using multivariate statistical methods

genetic diversity is necessary for breeding program and increasing genetic gain of selection in crop plants. with the onset of spring growth, spring cold stress is a problem for wheat crops at heading and also may be damaged some other parts of this plant. the aim of this study is the investigation of genetic diversity duo to artificial cold stress on the physiological traits, chlorophyll a, chlorophyll b, total chlorophyll, carotenoid and cytoplasmic membrane stability at the reproductive stage. for this purpose an experiment with 20 cultivars of bread wheat and four levels of cold stress, (8 (control), +2, 0 and -2 celsius) was performed in factorial arrangement in a completely randomized design. results of variance analysis showed the effects of interaction between cultivars and cold stress levels is significant at the 5% level which showed the existence of genetic diversity between studied cultivars.. there were significant correlations between chlorophyll a, b, total and carotenoid. in order to determination of genetic relation between cultivars, cluster analysis using was performed ward method and cultivars were divided into 5 groups at -2 °c and 4 groups at +8 °c. discriminate function and principal component analysis confirmed the results of cluster analysis. the third group of -2 °c including of ghods, tajan and pishtaz had the lower level of ion leakage and higher level of plant pigments.