Improving maize (Zea mays L.) genotypes for higher productivity and tolerance to drought stress depends mainly on physiological and molecular markers. Therefore, this study aims at breeding maize for drought tolerance and high potentiality by selection based on molecular markers, photosynthetic parameters; and easy graphic methods that help in selecting elite genotypes across diverse environments. An 8 × 8 half diallel analysis was used at two locations involving drought and normal irrigation treatments to study parental genetic diversity (GD) and combining ability (general combing ability [GCA] and specific combining ability [SCA]) in F1 of maize. Fingerprinting of parents was made using simple sequence repeat (SSR) markers. Fiftyeight alleles were ranged from two to five alleles per locus with an average of 0.63 alleles per locus. The average of polymorphic information content (PIC) was 0.63. Cuvette temperature (oc) was lowest by the cross L14 × L36. The cross L8 × L34 expresses the highest value for Quantum sensor (μmol m -2 s -1 ), net CO 2 assimilation rate and chlorophyll content. As for leaf diffusive resistance (LDR) four crosses exhibited significant desirable LDR values. Concerning rate of leaf transpiration (LTR) (μg cm −2 S −1 ) the cross (L5 × L104) gave the lowest value. Most hybrids exhibited desirable values for drought susceptibility index. For grain yield plant -1 , five F 1 crosses, that is, L5 × L34, L8 × L14, L8 × L14, L30 × L104, and L36 × L104 expressed the most desirable SCA effects. These crosses are promising in maize breeding programs. Based on GGE biplot analysis, genotype nos. 8 and 10 exhibited the highest grain yield plant −1 and ranked the first across all environments.

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The field experiments were carried out in two successive summer seasons of 2014 and 2015 at the experimental farm of the Faculty of Agriculture, Menoufia University, in El-Raheb, Egypt to evaluate yellow inbreed lines of maize through line x tester analysis. Top crosses were made each of the twenty-five S4 lines and the two testers by hand to give a total of 50 top crosses in 2014season. In the second season (2015) two adjacent experiments were conducted under two plant densities. The first experimental represented a normal plant density (ND) of 24000 plant/fad., (hills spaced 25 cm apart and one plant/ hill). The second experimental represented plant density (HD) of 30000 plants/fad. (hills spaced 20 cm a part and one plant hill). In each experiment the 50 top crosses as well as the two checks hybrids Giza 168 and Giza 176 were grown in a Randomized Complete Block Design with three replications. Performance of inbred lines varied with plant densities. Parental lines L3, L4, L5, L14 and L23 were the best in mean performance and general combining ability effects under this study. Results indicated that σ² SCA was more important than σ² GCA for all studied traits, plant height at the combined analysis. Non-additive gene action was more affected by the interaction with environments than the additive effects. The top crosses L12 x T2 and L17 x T2 showed desirable significant SCA effects for shortness and the low ear placement under low plant density. Thirteen top crosses showed significant positive SCA effects for grain yield (ard/fad) under HD, LD and combined analysis. Also, the top crosses L1 x T2 and L11 x T2 were significant under high plant density. The top crosses (L3 x T1 and L14 x T2) and (L3 x T2) showed significant number of ears per plot and 100-kernel weight relative to two check varieties for the top cross L3 x T1 gave the higher value of heterosis relative to the two checks for ear weight and grain yield.

Generation mean analysis was used for study the natural of gene action for yield and its attributes in three hybrids of bread wheat. Six parameters model was used in three wheat hybrids under optimum sown (25 th Nov.) and late sown (25 th Des.). The results cleared that the (P1, P2, F1, F2, Bc1 and Bc2) mean values in late sown were less than the optimum sown for all the studied characters in all hybrids. Heterosis relative to midparent and better parent was found to be positive significant for most characters under optimum and late sowing dates. The relative consequence of additive and dominance effects differed for characters in all hybrids under two different sowing dates. Dominance effects were generally more important than additive for most the characters in all the studied hybrids under two different sowing dates. Indicating, dominant genes played a part in the inheritance of these characters. Dominance × dominance gene interaction was higher in extent than additive × additive and additive × dominance in most the studied traits under two different sowing dates. Indicating, these traits are greatly influenced by dominance and dominance x dominance interactions. Therefore, it is approved to lateness selection to late segregating generations to raise homozygosity. Heritability values in narrow sense were moderate to high for all the studied characters in all hybrids under two different sowing dates. Genetic advance was ranged from low to high for all characters in all hybrids under two different sowing dates.