Study of Correlation and Causal Relations Quantitative Traits in Maize (Zea mays L.) in Normal and Heat Stress Conditions

In order to identify the most important traits affecting yield in maize inbred lines and hybrids, an experiment was conducted in Shushtar City in 2009 and 2010 years. Fifteen inbred lines in 2009 and 28 hybrids in 2010 studied in two planting dates, 6 July (to coincide heat stress with pollination time and grain filling) and 27 July (normal condition) using a randomized complete block design with three replications. Stepwise regression results indicated that in inbred lines in heat stress condition grain number in ear, tassel branching out number and grain protein percent traits and in hybrids grain dry matter weight, grain depth and pedunkel length leaf inner in model were input. In normal condition in inbred lines grain filling period and grain row number traits and in hybrids only grain filling period in model were input. In stress condition in inbred lines grain number in ear, in hybrids grain dry matter weigth and grain depth and in normal condition in inbred lines and hybrids grain filling period trait highest direct effect and positive on grain yield indicated. In general, it seems that traits highest direct effect on genotypes in either condition, is a suitable criterion for evaluationg the productivity of maize genotypes and in breeding programs should to consider for production grain yield.