Weeds are severely competition with wheat crop and it highly reduces crop yield. So, the present study was conducted on wheat cultivations during two seasons 2013/2014 and 2014/2015 to evaluated phytotoxicity effects of some herbicides on wheat (Triticum aestivum). Effectiveness of these herbicides on weed control in wheat crop and yield evaluation and quality of wheat was evaluated as well after treatment by herbicides. The field experiment was carried out in agricultural experimental station of Etay El-barod, El-Beheira Governorate, using randomized complete block design (RCBD) with four replicates for each treatment and unweeded check, having two rates of both herbicide recommended and double recommended rates (R, 2R). Treatments comprised of post-emergence application of pyroxsulam, flumetsulam+ florasulam, tribenuron-methyl, diclofop-methyl and tralkoxydim. The results indicated an increase in wheat plant height with all herbicides used compared to unweeded check. Tribenuron-methyl and flumetsulam + florasulam treatments did not cause any visible phytotoxicity, while pyroxsulam, diclofop-methyl and tralkoxydim treatments recorded a low indexes of phytotoxicity on wheat plants which disappeared completely after 8 weeks from post application, compared to unweeded check. Results also, indicated that all herbicide treatments decreased weed density. Herbicide treatments achieved the highest weed control expressed in lowest fresh weight after 56 days from application for broadleaved, grassy and  total weeds. Herbicide treatments caused an excellent increase in yield attributes (spike length, biological and grain yield) and yield quality (weight of 1000 grains, total carbohydrates and crude protein) compared to unweeded check in both seasons. The maximum grain yield was recorded at two trials by pyroxsulam compared to unweeded check.

Twenty one wheat hybrids and their seven parental genotypes were evaluated in the research farm of the Faculty of Agriculture, Ain shams University, Shoubra El-khema, Cairo, Egypt, in 2016/2017 growing season. The genetic analysis was conducted using Griffing (1956), Method 2, model 1).                 Significant differences among parent genotypes and their 21 crosses for all the studied traits (days to 50% heading, days to maturity, flag leaf area, plant height, number of spikes/ plant, spike length, number of spikelets/ spike, number of kernels/ spike, 1000-kernel weight and grain yield/ plant) were detected. This indicated that, variability exists among these populations may increase the chance appearance of good new combination that can be isolated in the succeeding generations. Parents versus crosses mean squares as an indication for average heterosis over all crosses were significant for all studied traits.                 Mean squares of general (GCA) and specific (SCA) combining abilities were significant for all studied traits except spike length trait for SCA which was insignificant. GCA/SCA ratios were more than unity for all studied traits, which indicating that the additive type of gene action is of great importance in the inheritance of these traits. Heterosis over the better parents showed that, the best hybrids were Gemmiza 9xGiza 168, Sakha 93x Giza, 168, Sakha 94x Jawahir-14, Sakha 94x Bob white, Giza 168xAcsad 925 and Jawahir-14x Bob white for grain yield/ plant trait and some of the other studied traits. The best general combiner parents were Sakha 94, Jawahir-14 and Bob white for grain yield/ plant trait and some of the other studied traits. The best SCA hybrids were Gemmiza 9x Sakha 93, Gemmiza 9x Giza 168, Sakha 93x Jawahir-14, Sakha 94xJawahir-14, Sakha 94x Acsad 925, Sakha 94xBob white, Giza 168x Jawahir-14, Giza 168x Acsad 925, Jawahir-14x Bob white and Acsad 925x Bob white for grain yield/ plant trait and some of the other studied traits. These result could be used in wheat breeding programs.

A 7x7 half diallel cross along with their parental wheat cultivars were evaluated under two sowing dates (19th Nov. and 17th Dec.).The results revealed that mean squares due to sowing dates, genotypes and genotypes x sowing dates interaction were significant for most of the studied traits. Delaying sowing date to Dec. reduced all studied characters compared to the normal sowing date except electrolyte leakage which increased by delaying sowing date. Heterosis over better parents showed that, the best hybrids under stress condition were Misr 2 X Giza 168 and Sids 1 X Giza 168   for grain yield / plant and some of other studied traits.  General and specific combining ability mean squares indicated the importance of both additive and non-additive gene effects in the inheritance of the studied traits with few exceptions. However, the additive effect was more important than the non-additive effects in the inheritance of days to 50% heading, plant height, No. of spikes/ plant,No. of kernels / spike and 1000-kernel weight while, the non-additive effects were more important than the additive effects in the inheritance of electrolyte leakage and flag leaf area. The best general combiner parents for grain yield / plant and some of other studied traits were Gemmeiza 11 and Giza 168under stress condition. The best hybrids for SCA effects were Sakha 93 X Sids 1, Gemmeiza 11 X Giza 168, Misr 2 X Giza 168 and Sids 1 X Giza 168 under stress condition for grain yield / plant and some of other studied traits. The crosses Gemmeiza 11 X Giza 168   (HSI 0.36), Gemmeiza 7 X Giza 168   (HSI 0.58) and Sakha 93 X Giza 168   (HSI 0.60) have recorded the lowest values of heat susceptibility index (HSI), indicating their tolerance to heat stress (late sowing date).