Özet:

Maydis leaf blight MLB , caused by Bipolaris maydis, is one of the most important diseases in maize. The objectives of this study were to quantify the progress for maydis leaf blight resistance improvement by estimating selection differential, expected and observed responses to selection after two cycles of S1 line recurrent selection, and to estimate heritability for various morphological and yield traits in "Azam" composite maize population. This study was conducted at the research farm of Agricultural University, Peshawar, Pakistan during summer 2006 and 2007. In cycle3 about one hundred S1 lines while in cycle-4 196 S1 lines of maize population Azam were evaluated under epiphytotic conditions along with their progenies in lattice square design with two replications. Highly significant variations were observed among the S1 lines for grain yield, MLB, plant height, ear height, ear length, kernel rows cob-1, and maturity traits in two cycles. In cycle-3 the expected and observed responses for grain yield 432, 2144 kg ha-1 , MLB -0.53, - 0.65 , plant height 1.65, 28cm , ear height -0.43, 10 cm , ear length 0.78, 5 cm , kernel rows cob-1 -0.29, 2 , pollen shedding -0.21, -5 days and silking -0.09, -4 days were observed, while in cycle-4 expected and observed responses were 715, 2762 kg ha-1 , -0.01, -0.13 , 1.15, 41 cm , 0.44, 23 cm , 1.17, 3 cm , 0.07, 1 , -1.23, -2 days and -1.39, -1 days for the above traits, respectively. In both cycles the heritability values were estimated for grain yield 0.50, 0.64 , MLB 0.84, 0.52 , plant height 0.62, 0.79 , ear height 0.63, 0.47 , ear length 0.58, 0.55 , kernel rows cob-1 0.63, 0.62 , pollen shedding 0.83, 0.83 and silking 0.72, 0.82 . The increased performance of the progenies of selected S1 lines manifests the efficiency of breeding program and suggests that S1 line recurrent selection would be the most efficient method for improving MLB resistance and grain yield simultaneously in maize population Azam.

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