Selection of Old and New Varieties of Bread Wheat Tolerant to Drought Stress after the Flowering Stage

In semi-arid areas such as a large part of Iran, due to rainfall unfavorable distribution and temperature sudden increase in time of grain filling, soil moisture decrease is considered as one of the most important factors in the reduction of wheat growth and development, Therefore, by evaluating the effects of drought stress on the studied cultivars, it is possible to identify the most favorable cultivars and use them for future breeding purposes. Therefore, the purpose of this research was to identify drought tolerant cultivars and their characteristics with the help of drought tolerant indices that cause higher yield in dry climatic conditions.

The present experiment was designed and implemented in the educational-research farm of Payame Noor University, Asadabad center, in the form of a randomized complete block design with three replications in two conditions of moisture treatment in the crop year 2015-2016. Moisture treatment was carried out in the conditions of drought stress in the form of interruption of irrigation after flowering and in conditions without drought stress. Were used in this research number 14 cultivar of old and new varieties of bread wheat. Drought tolerance indices were used in this research.

The results of mean comparing of this experiment showed that the highest mean yield in the conditions without drought stress and drought stress condition was cultivar No. 10 and 2, respectively. Cultivar No, 10, 2 and 6 had the highest Stress Tolerance Index, Mean Productivity, Geometric Mean Productivity, Harmonic Index, Abiotic-Stress Tolerance Index, Modified Stress Tolerance index in without Drought Stress, Modified Stress Tolerance Index in Drought Stress and Stress Tolerance Score Indices. The results of the correlation analysis between the indices and the mean yield in the non-drought stress conditions and drought stress condition showed that the most suitable indices for screening cultivars in two environmental conditions were STI, ATI, K1STI, K2STI, STS, MP, HAM and GMP.Also, Principal Components Analysis showed that 69.3% of the changes of the examined variables in the of non-drought stress conditions and drought stress conditions can be explained by the first component and 99.4% of the said changes can be explained by the first and second components.

In this study, STI, ATI, K1STI, K2STI, STS, MP, HAM and GMP indexes were found to be favorable. Therefore, these indices were able to identify drought tolerant cultivars with optimal performance in both environmental conditions under investigation (non-drought stress conditions and drought stress conditions). The cultivars that were able to be selected in both environmental conditions by the mentioned indices included cultivars No. 10, 2 and 6, respectively.