This experiment was carried out on the basis of complete randomized block design with three replications and 15 foreign hybrids new hybrids of corn in addition 3 commercial hybrid (as control) under normal sowing date and delayed sowing date condition in the Khorasan Razavi Agricultural Research Centre, Iran in the year 2008. This study showed that among all hybrids, EXP1 (18.61 ton/ha) and SIMON (17.91 ton/ha) had the highest yields in early planting (5 th June) and EXP1 (14.01 ton/ha) and

more »

... ON (13.06 ton/ha) produced the highest yields in late planting (20 th June). According to principal component analysis, four principal components (PC) had Eigen values >1 which accounted for 67% of the total variance in the data on early planting date and 73% of the total variance in the data on delayed planting date. The results obtained from the factor analysis identified 12 factors out of which only four were extracted which together explained 67.8% of the variance among the entries on the first planting date, and five factor in total 73.33% of the changes were justified on the second planting date. Based on cluster analysis, the 18 corn hybrids were separated into four and five major groups with each having two or more subgroups on early and delayed sowing dates respectively. Based on the present results, it was recommended to make crosses among genotypes in Clus1, Clus2 and Clus4, while Clus5 was made on both planting dates in breeding programs.