Morphological Classification of Maize (Zea mays L.) Genotypes in Heat Stress Condition

This experiment was set up to understand genetic diversity in maize hybrids under heat stress condition. 30 morphological traits of 28 hybrids were studied in a randomized complete block design with three replications in 2010 at two planting dates, 6th July (to coincide heat stress with the pollination and grain filling periods) and 27th July (normal) in Shoushtar City in the southern part of Iran. The results showed that the traits of grain filling period, plant growth period, rows per ear and grains per ear in the both conditions had positive and significant correlation with grain yield. Under heat stress condition however, the highest coefficient of phenotypic variation was obtained for grain yield, grains per ear, grains per row and ASI, and in normal condition for grain abortion percentage and ASI. Cluster analysis by Ward’s minimum variance, clustered hybrids in to three groups for both conditions. Hybrids K18×K166B and K18×K47/2-2-1-21-2-1-1-1 in the second cluster from the heat stress condition and hybrids K18×K166B, K166A×K3640/5, K166A×K47/2-2-1-21-2-1-1-1 and K166A×K19 in second cluster from the normal condition were found to be the most suitable because they had higher values for grain yield and other desirable traits and lower grain abortion percentage, ASI and grain protein percentage. Therefore, in accordance with the cluster analysis these aforementioned hybrids would be the most suitable for cultivation under the studied conditions.