Preliminarley yield trail of late and medium maturing maize hybrids

75 different hybrids were eval uated in three trails (A , B and C) of each 25 hybrids. Each of these three trails,was conducted under two density (Normal= 65000 and high = 100000 ptants/ha) seperatety using randomized complet block design in three replications. In trail A,under normal density,early flowering hybrid 24 and late flowering hybrid 23 produced 13.940 and 13.900 ton/ha,respectively.The earliest hybrid 10,p roduced the highest yield (14.980 ton/ha). Under high density in trail A,againg,hybrids 10 and 24 by 14.100 and 12.450 tons/ha, respectively, produced the highest grain yield,which shws the stability of these hybrids for grain yield under both densities. Under normal density of trail B,hybrids 18,3 and 17 produced the highest yield by 12.230,13.110 and 13.100 tons/ha,respectively.Hybrids 3 and 17 also under high-density produced high yield,but,hybrid-18 in this condition had -low yield-¬which showed stability of hybrids3 and 17 and unstability of hybrid 18. The high yielding hybrid 3,had high number of rows/ear.Comparing the means showed showed that very high and very low 1000 kernel weight may decreas the grain yield,but decreasing the number of rows/ear and number of kernels/row evantually will decreas the grain yield. in trail C,under both densities.hybrio 18 produced the high:yieid(13.060 and 13.440(tonS/ha ,respectively)wnich shows the stability of grain yield in this hybrid.This hybrid has low days to flowering and maturity and also,its plant and ear height are low. Genetical analysis of trail A using Line X Tester analysis showed the main role of dominant variance for grain yield and number of rows/ear. Testers A and C showed good general combining ability(GCA) for increasing and tesr B for decreasing the number kernels/row. Tester B showed good GCA for increasing the number of kernels/row and tester C for increasing the grain yield and row number/ear.ln trail C,lines 5 and 7 under both densities show neqatlve GCA for days to flowering 'which can be used to decreasing this character.ln opposite, lines 3 and 4 with positive GCA are good sources to increasing this period.Additive variances for this trait were significant under both densities. Tester A has negative and tester 8 has positive GCA for number of rows/ear under both densities.But fornumber of kemels/row,tester A and B have positive and negative GCA,respectively.