MajidVakil Asadolaei, BahramMajd Nassiri, Maryam Yousefifard
Faculty of Agriculture, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran
Isfahan Agricultural and Natural Resource Research Center. Isfahan, Iran
Department of Environment and Natural Resources, Payame Noor University, PO BOX 19395-3697, Tehran, Iran
Key words: Sunflower, Drought tolerance, Genetic improvement, Path analysis, Selection indices.
Randomized complete block design with four replications in two drought and non-drought environments was used for this study. Drought resistance indices were calculated based on seed yield in stress and non-stress conditions. The results showed that GMP and STI were the best drought resistance indices so had the positive and significant correlation with Yp and Ys. Three dimensional graph showed that RFG5*AF80, G-543 and Farokh were the drought resistant hybrids. These hybrids had the highest amount of Yp, Ys, GMP and STI that revealed the highest yield potential as well as drought tolerance in these genotypes. Because of that these hybrids have promised potential to cultivate in drought prone environments. Regression analysis revealed that the traits grain filling rate, grain filling duration and water use efficiency accounted for 97.0% of total variation exist in seed yield. Path coefficient analysis demonstrated the highest and positive direct effect of grain filling rate and grain filling duration on seed yield in sunflower hybrids. Water use efficiency had low direct effect while high indirect effects via grain filling duration on seed yield. Therefore, the study revealed the importance of total grain filling rate and grain filling duration as indirect selection criteria for genetic improvement of seed yield in sunflower breeding programs especially in early generations. On the other hand, indirect effects of water use efficiency through grain filling duration on seed yield have promising result in selection programs.
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