الفهرس 
Sowing dates effect on wheat traitsOnly 14 pages are availabe for public view
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Abstract
This study was coducted at El-Gemmeiza research station farm, El-Gmeaiza, Gharbiah Governorate, Egypt, during the two successive growing seasons 2015/2016 and 2016/2017. Eight common wheat cultivars, Triticum aestivum L. em Thell, were choosen for this study were in a half dilele crosses to estaimates heterosis and combining abilty assosited with grain yield and its component under the three sowing dates of 30th October (1st sowing date), 15th November (2nd sowing date, 1st December (3rd sowing date) and their combined analysis to determined the most stable perants and crosses with high grain yield. Also, to determined the pest method of selection will be used in the segregation generation The obtained results of this study could be summarized as the follows:
1- Analysis of variance 1) Mean squares due to sowing dates were highly significant for all traits studied indicating as expected that the differences between the three sowing dates were markedly differed 2) Mean squares due to genotypes were found to be highly significant for all studied traits at the three sowing dates as well as their combined analysis, except for spike length in 2nd and 3rd sowing date and number of spikelets/spike and grain weight/spike in the combined analysis. The genotypes interaction with sowing date was also found to be highly significant for all studies traits 3) Mean squares of parents were highly significant for all traits studied at the three sowing dates as well as their combined analysis except for spike length in 1st sowing date, 2nd sowing date and combined analysis, number of spike/plant, number of spikelets/spike, grain weight/spike and 1000-grains weight in the combined analysis. In the same line mean squares due to interactions between parents and sowing dates were highly significant for all studied traits 4) The result showed that the crosses mean squares were highly significant for all traits studied at the three sowing dates as well as their combined analysis except for spike length in 2nd, 3rd sowing dates and the combined analysis and grains weight/spike in the combined analysis. In the same way significant mean squares due to interaction between crosses and sowing dates found to be highly for all studied traits 2- Mean performances:
1) It was clear for the earliness (heading and maturity date (days)) the parental variety Sakha 61 followed by Sakha 94 and Gemmeza 12 showed the earliest desirable mean values at the three sowing dates and their combined data 2) The results showed that that the three parents Giza 171, Sakha 94 and Misr 1 were the best because it score a desirable mean performance in yield (straw and grain) and most yield components at the three sowing dates and the combined data 3) For harvest index, the highest harvest index scored by the parent Sids 13 in 1st sowing dates, Shandweel 1 in the 2nd sowing date and combined data and Gemmeza 12 in the 3rd sowing date 4) The most desirable and/or highest mean performances for all crosses in all traits studied the three sowing dates and their combined data were defined. It was identified for the earliness (Heading and maturity date (days)) the cross combinations between Sakha 61 and all other parental genotypes showed the earliest desirable mean values the three sowing dates and their combined data 5) It could be concluded that the cross combinations of Sakha 94 with the three parents Misr 1, Sakha 61 and Gemmeza 12 were the best because it score a desirable mean performance in grain yield and some of its components and in most others traits in the three sowing dates and the combined data 6) For harvest index, the highest mean values scored by the crosses Gemmeza 12 * Shandaweel 1, Gemmeza 12 * Sakha 94 and Sakha 94 * Misr 1 in the combined analysis and one or more of the three sowing dates 3- heterotic effects:
1) parents vs. crosses mean squares were found to be highly significant for all traits studied at the three sowing dates and their combined data except for maturity date (days) in the 1st sowing date, number of tillers /plant in the combined analysis, spike length in the three sowing dates and their combined analysis, number of spike /plant in the 3rd sowing date and combined analysis, number of spikelets/spike in 2nd, 3rd sowing dates and combined analysis, grain weight/spike in 2nd, 3rd sowing dates and combined analysis, 1000-grains weight in 2nd sowing date and biological, straw, grain yield/plant and harvest index in the combined analysis 2) The mean square of the interaction of average heterosis x sowing dates (parent x F1 x sowing dates) was found to be significant for all studied traits except for spike length 3) Respect to heading date (days), the most desirable significant negative heterosis were obtained by the cross Sakha 94 * Misr 1 followed by the cross Sids 13 * Sids 1and Misr 1* Sids 13 4) The most desirable significant of heterosis relative to bettet-parent obtained for maturity date (days), by the cross Shandaweel 1 * Giza 171 gave significant negative desirable heterosis relative to better-parent in the three sowing dates and the combined analysis
5) The three crosses, Gemmeza 12 * Sakha 61, Shandaweel 1 * Sids 13 and Sakha 61 * Misr 1 gave highly positive desirable values of heterosis relative to better-parent for For grain yield /plant (g) and som of its components in the combined analysis and one or more sowing date. 4- Combining abilities:
4.1- Analysis of variance for combining ability:
1) The mean squares due to general combining ability were highly significant and/or significant at the three sowing dates and their combined analysis for all studied traits except for spike length in the 1st, 3rd sowing date and the combined analysis, number of spikelets/spike in 3rd sowing date and the combined analysis and 1000-grain weight in the combined analysis 2) The mean squares due to specific combining ability were highly significant and/or significant for all traits at the three sowing dates and their combined analysis except for spike length in the three sowing dates and their combined analysis, number of spikelets/spike in the combined analysis and grain weight /spike in the combined analysis 3) The ratios of GCA / SCA exceeded the unity were detected for all traits at the three sowing dates and their combined analysis, except spike length in the 3rd sowing date and the combined analysis, number of spike/plant in the 3rd sowing date, number of spikelets/spike in the three sowing dates, biological yield/plant in the 3rd sowing date and number of grains/spike and 1000-grain weight in the three sowing dates and their combined analysis. The ratio of GCA / SCA which largely exceeded the unity may indicate that the largest part of the total genetic variability associated with these traits a result of additive and additive x additive gene action. While the excepted traits the non-additive gene effects seamed to be responsible to inheritance of the trait in question 4.2- General combining ability effects:
It could be detected that the breeder can be used the four parents Misr 1, Sakha 94, Sakha 61 and Gemmeza 12 to improve yield and earliness by releasing it in crossing programs 4.3 - Specific combining ability effects:
The breeder could be relasing the five crosses Gemmeza 12 * Giza 171, Sakha 94 * Sids 1, Gemmeza 12 * Shandaweel 1, Sakha 94 * Misr 1 and Sakha 61 * Sakha 94 grain yield/ plant in breeding program to segregate early lines with high grain and straw yield, where it gave significant positive (Ŝij) values for grain and straw yield and some of its components in the three sowing dates and their combined analysis FAINALLY: pidgree method of selection will be an excellent method for breeders to select good lines with high yield and stability to a wide range of sowing dates in baised of yield and yield components traits.