مطالعه همبستگي صفات و تجزيه عليت عملكرد دانه در هيبريدهاي ذرت در شرايط آبياري و كم آبياري

Evaluating causal relations in grain yield of corn hybrids under normal soil moisture and drought stress condition

In order to evaluate responses of different corn hybrids to drought stress and to detect relations and correlations between different traits in studied genotypes, a study was conducted in northern west of Qom province, near to Shokohieh suburb during 2007. Twenty corn hybrids were evaluated using a complete randomized block design with four replications and in two distinct experiments under normal soil moisture and drought stress (irrigation after depletion of 30 and 60 percent of soil moisture, respectively). Analysis of variance of studied traits in normal and drought conditions denoted existence of appreciable diversity in these traits among corn hybrids. The highest variation between two environments was belong to anthesis-silking interval (ASI) (-51.62%), and yield variation was 31.72%. In both conditions, heritability of kernel weight, hectoliter and grain yield were higher than other traits. Assessing correlations between traits in normal condition showed there is a positive, significant correlation between yield with hectoliter weight, kernel weight, kernel rows in ear, and kernels in row. Under drought stress, there was a high negative correlation between yield and ASI (-0.83), and also days to silking and tasseling, whereas grain yield showed positive correlation with kernels in row (0.82), kernel rows in ear (0.75), and also kernel depth and weight. Studying direct and indirect effects of traits effective in normal condition indicated that the highest direct effect on grain yield was related to kernels rows (0.868). In stress condition, however, direct effects of kernels in row (0.778) and kernels in ear were positive and higher than others, and direct effect of tassel peduncle length in inverse proportion on yield was more than other traits. ASI had a strong effect on yield reduction in stress condition, indirectly by reducing kernel number. According to results, the best way to selection toward yield enhancement is the direct selection in order to increase yield components, and in screening drought tolerant crops, a special attention should be paid to reducing ASI duration, and also days to silk and tassel appearance.