الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
Fourteen bread wheat varieties were crossed in a line x testers analysis (10 lines and four testers) to obtain 40 F1’s hybrids to evaluate combining ability and genetic components in F1 hybrids under normal (80 kg N/fed) and low (40 kg N/fed) levels of nitrogen fertilization. Results cleared that genotypes, parents and crosses mean squares were found to be highly significant for all traits studied and also, their interactions with the two levels of nitrogen fertilization. Parent vs. crosses mean squares were found to be highly significant for all traits studied except, number of grains per spike under low-N. Lines, testers and line x testers mean squares and their interaction with nitrogen levels were highly significant for all traits studied. The parental line Gemmeiza 11 (L3) was a good combiner under low-N for all traits studied except, 1000-grain weight. The parental line Misr 1 (L6) for 1000-grain weight and grain yield per plant. The parental line Gemmeiza 12 (L10) for number of spikes per plant, 1000-grain weight and grain yield per plant. The tester Sids 12 (T2) was a good combiner number of grains per spike, 1000-grain weight and grain yield per plant and the tester Giza 168 (T4) for number of spikes per plant, 1000-grain weight and grain yield per plant under low-N. The desirable SCA effects were detected by twelve hybrids. The GCA/SCA ratio were less than unity at both levels of fertilization for all traits studied, indicating that non-additive gene effects in controlling the inheritance of all the traits studied.