Analysis of grain yield and its attributes in bread wheat and their associations with coleoptile length under water deficit conditions

Introduction To investigate water stress tolerance indexes, estimation of genetic diversity for coleoptile length and other agricultural variables such as grain yield and its components and also investigating of the role of coleoptile length in response to water stress and its relation to yield and its components in wheat cultivars in arid and semi-arid regions of Iran. Materials and methods This study was performed in a randomized complete block design with 3 replications and 50 wheat genotypes under stress and non-stress water conditions. In this evaluation, the STI index was calculated based on grain yield of genotypes under stress conditions. For investigating the association of traits and drought tolerance index with coleoptile length the coefficient of correlation was calculated Analysis of variance of genotypes was performed using SAS software (ver. 9.1) for all traits. Results and discussion Analysis of variance showed that there was a significant difference between genotypes for plant height, days to heading, grain yield, spike weight, awn length, grain per spike, 1000-grian weight, and spike length in both stress and non-stress water conditions, however this was not significant for number of spike per unit. The results showed that except for awn length and spike weight, mean values of all traits in non-stress conditions were more than stress condition. The coleoptile length of genotypes was variable from 2.41 cm to 4.91 cm. The range for all traits in both stress and non-stress conditions was relatively high which indicated a high diversity between the studied cultivars. Among the nine studied traits, six of them suffered a decline in growth due to drought stress and so that reduction in number of spike with 4.38%, grain yield with 13% and spike weight with 14% were more obvious. In this evaluation, the STI index was calculated based on grain yield of genotypes under stress conditions. Six cultivars including Shirudi, Orum, Pasteur, S-90-5, Ofogh, and Sistan were the most tolerant and cultivar Star had the least amount of STI index. The highest positive correlation of coleoptile length.in both environmental conditions was occurred about plant height and number of spike. Correlation coefficients of plant height with coleoptile length under stress and non-stress conditions were was 0.56 and 0.43, respectively, and its correlations with number of spike were 0.16 and 0.165, too. A negative correlation between coleoptile length and STI index was observed in both stress and non-stress conditions. The correlation coefficient of coleoptile length with some agronomic changed in terms of size and direction over stress than non-stress conditions, therefore this could be inferred to effective role of coleoptile in the balance of plant and moisture conditions. Conclusions In general, the results of this study showed that the cultivars had a significant difference between sowing date and spike appearance, plant height, spike length, spike weight, 1000-grian weight, awn length, grain per spike and grain yield.