Study of Chilling Tolerance in Rice Cultivars at Seedling Stage Using Morphological and Physiological Characteristics

Cold stress is one of the most important environmental stresses for rice especially in temperate and high elevation areas. In present study, the effect of different temperatures, as the main plot, including 25 (control), 10 and 5°C on 12 rice cultivars (including Champa Yasouj, Gerde, Lenjan Askari, Kaamfirouz, Kohsar, Shafagh, Domsiya Mamassani, Dular, Gharib, Hasan saraei, Mosa Tarom and 304) as the sub plot, was investigated using a split plot experiment based on a completely randomized design with 3 replications. According to the results of ANOVA, the effects of temperature, cultivar and their interaction were significant for all measured traits, indicating that there was high genetic diversity among the studied cultivars. Means of all studied morphological traits decreased in cold stress condition relative to non-stress condition. Genotypic and phenotypic correlation coefficients showed that shoot (seedling) related traits such as shoot fresh and dry weights and shoot length could be used for indirect selection for chilling tolerance in cold stress conditions at seedling stage. Based on cultivar grouping using the 3-dimensional plot of STI, YS and YP, Gharib and Champa Yasouj cultivars were identified as the most suitable cultivars in both cold stress and non stress conditions. Most of the studied cultivars including Gerde, Lenjan Askari, Kaamfirouz, Kohsar, Domsiya Mamassani, 304, Mosa Tarom and Hasan Saraei were found to be chilling sensitive cultivars at the seedling stage. Therefore, crosses between chilling resistant (Gharib and Champa Yasouj) and chilling sensitive cultivars will be useful for detecting transgressive segregation and improving cold stress tolerance in rice breeding programs.