الفهرس 
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Abstract
This investigation was carried out at the experimental farm of Sakha and Sids Agricultural Research Station, ARC, Egypt. during the two successive growing seasons 2011 and 2012. In 2011 season, 16 new yellow maize inbred lines were top-crossed with three testers according to line x tester mating design to produce 48 F1 hybrids. Two yield traits conducted at both locations in a disease nursery under artificial soil inoculation by the pathogen Cephalosporium maydis which causes late wilt disease in 2012 season.
The 48 top-crosses a long with two checks hybrids SC-168 and TWC-353 were evaluated under two locations in a RCBD with 4 replications. Line x tester analysis as proposed by Kempthorme (1957) was used for partitioning the genetic variation of the top-crosses and estimate general and specific combining abilities of the parents and crosses.
The following data were recorded: days to 50% silking, plant height (cm), ear position%, resistance to late wilt disease, number of ears per 100 plant, ear length (cm), ear diameter (cm), number of rows per ear, number of kernels per row, weight of 100 kernels (g) and grain yield (ardabs/fed).
The obtained results could be summarized as follows:-
1- Days to 50% silking:
• The mean squares of locations (Loc.), (G), (C), (Ch.) and (C vs. Ch.) were highly significant under the two locations and their combined data except for C vs. Ch. at Sids location was not significant. Mean squares due to lines (L), testers (T) and their interaction (L x T) were significant to highly significant under the two locations and their combined data.
• The combined data for days to 50% silking showed that 12 single crosses decreased significantly than the check SC-168 toward earliness.
• The additive variance played a major role than the non-additive genetic variance in the inheritance of these traits. Additive type of gene action was more influence by environment than non-additive gene action.
• Inbred lines (Sk 5011/14) and (Sk 5021/19) had desirable significant toward earliness for two locations and their combined data. The crosses (Sk 5003/6 x comp-9), (Sk 5022/20 x Sk-11) and (Sk 5009/11 x Sk-11 and Sk 5019/16 x Sc-162) had desirable values (negative) at Sakha, Sids and their combined, respectively.
• The results showed that 15 single crosses, 12 single crosses and 13 single crosses at Sakha location, Sids location and the combined data were negative significant superiority toward earliness.
2- Plant height (cm):
• The mean squares due to locations (Loc.), (G), (C) and (Ch.) were highly significant under the two locations and their combined data except for Ch. at the two locations was not significant. Mean squares due to lines (L), testers (T) and their interaction (L x T) were significant to highly significant under the two locations and their combined data. The results revealed that the interaction among L, T and L x T with locations (Loc.) were not significant except for L x Loc.
• One single cross (Sk 5002/4 x Sk-11) shorter significantly than the check SC-168, in addition to seven single cross shorted but not significantly while, five three way crosses (Sk 5002/1 x SC-162, Sk 5002/4 x SC-162, Sk 5018/15 x SC-162, Sk 5021/18 SC-162 and Sk 5021/19 x SC-162) shorter significantly than the check TWC-353.
• The additive genetic effects played a major role in the genetic expression of this trait. The additive gene action was more affected by environmental conditions than the non-additive gene action.
• Two inbred lines (Sk 5002/1) and (Sk 5018/15) had desirable (negative) significant to highly significant GCA effects at two locations and their combined data. The crosses (Sk 5018/15 x Sc-162 and Sk 5019/16 x Sc-162) and (Sk 5009/11 x Sk-11 and Sk 5018/15 x Sc-162) had desirable (negative) SCA effects at Sakha and the combined data.
• One single cross (Sk 5002/4 x Sk-11) and four three way crosses (Sk 5002/1 x SC-162, Sk 5002/4 x SC-162, Sk 5018/15 x SC-162 and Sk 5021/18 x SC-162) were negative significant superiority.
3- Ear position %:
• Mean squares of locations (Loc.), (G), (C) and (C vs. Ch.) were highly significant under the two locations and their combined data except for C vs. Ch. at Sakha location. Differences among lines (L), testers (T) and L x T were significant to highly significant at the two locations and their combined data except for L x T at Sakha and Sids locations.
• 11 single crosses characterized as better ear position significantly than the check Sc-168 while. Three TWC (Sk 5011/14 x SC-162, Sk 5019/17 x Sc-162 and Sk 5022/20 x SC-162) characterized as better ear position significantly than the check TWC-353.
• The additive variance played a major role than the non-additive genetic variance in the inheritance of this trait. Additive type of gene action was more influence by environment than non-additive gene action.
• Inbred lines Sk 5011/14, Sk 5019/17 and Sk 5020/20 had desirable estimate SCA effects toward best ear position for the two locations and their combined data. The cross (Sk 5003/6 x Sk-11) showed significant negative SCA effects at Sids and the combined data.
• 11 single crosses and 3 three way crosses were significant superiority toward best ear position.
4- Resistance to late wilt %:
• The mean squares of locations (Loc.), (G), (C) and (C vs. Ch.) were highly significant under the two locations and their combined data except for C vs. Ch. at Sids location and the combined data. The mean squares due to lines (L), testers (T) and their interaction (L x T) were highly significant under the two location and their combined data.
• Three single crosses Sk 5003/6 x Sk-11, Sk 5007/9 x Sk-11 and Sk 5009/12 x Sk-11 exhibited high resistance to this disease over 95% while, two three way crosses Sk 5002/4 x SC-162 and Sk 5019/16 x SC-162 resistance 100%. Four top crosses exhibited high resistance (over 95%).
• The additive variance played a major role than the non-additive genetic variance in the inheritance of this trait. Non-additive type of gene action was more influence by environment that additive gene action.
• Four inbred lines (Sk 5007/9, Sk 5003/6, Sk 5019/16 and Sk 5009/12) had favorable allels and significant estimate of gi effects toward resistance to late wilt disease. The crosses (Sk 5009/12 x Sk-11), (Sk 5011/14 x Sc-162) and (Sk 5007/9 x Sk-11 and Sk 5009/12 x Sk-11) were had positive significant SCA effects at Sakha, Sids and their combined, respectively.
5- Number of ears per 100 plant:
• Differences among locations were highly significant. The mean squares of genotypes (G), (C) and (Ch.) were significant to highly significant under the two locations and their combined data except for Ch. at Sakha and the combined data. The mean squares due to lines (L), testers (T) and their interaction (L x T) were highly significant under the two locations and their combined data except for L x T at Sids location was not significant.
• Two single crosses increased significantly than the check Sc-168 i.e. (Sk 5004/8 x Sk-11) and (Sk 5018/15 x Sk-11) while, seven three way crosses increased but not significantly than the check TWC-353.
• The non-additive genetic variance played an important role in the inheritance these traits. Non-additive type of gene action was more influence by environment that additive gene action.
• One parental line (Sk 5004/8) that had desirable highly significant GCA effects, as well as the inbred line (Sk 5004/7) under Sids location and the combined data. The crosses (Sk 5004/8 x Sk-11 and Sk 5009/11 x Sc-162), (Sk 5018/15 x Sk-11 and Sk 5021/18 x Sc-162) and (Sk 5004/8 x Sk-11, Sk 5009/11 x Sc-162 and Sk 5018/15 x Sk-11) had positive significant effects at Sakha, Sids and their combined, respectively.
• The results illustrated that at Sids location one three way cross (Sk 5021/18 x SC-162) and two single crosses Sk 5004/8 x Sk-11 and Sk 5018/15 x Sk-11for the combined data had significant superiority.
6- Ear length (cm):
• The mean squares among locations (Loc.) were highly significant. The mean squares due to (G), (C), (Ch.) and (C vs. Ch.) were significant to highly significant under the two locations and their combined data except for C vs. Ch. at Sids location and the combined. Differences among lines (L), testers (L) and L x T interaction were significant to highly significant at the two locations and their combined data except for L x T at Sakha location.
• Two single crosses decreased but not significantly than the check Sc-168 while, 14 three way crosses increased significantly than the check TWC-353.
• The additive variance played a major role than the non-additive genetic variance in the inheritance of these traits. These results indicating that non-additive type of gene action was more influence by environment that additive gene action.
• The three parental lines (Sk 5003/6), (Sk 5008/10) and (Sk 5009/11) had desirable significant to highly significant GCA effects under the two locations and their combined data. Crosses (Sk 5004/7 x Sc-162, Sk 5011/14 x Sc-162 and Sk 5021/18 x Sk-11) and (Sk 5004/7 x Sc-162 and Sk 5021/18 x Sk-11) had positive significant SCA effects at Sids and the combined.
• The results cleared that 11 three way crosses, 12 three way crosses and 13 three way crosses for Sakha location, Sids location and the combined data, respectively had positive significant superiority.
7- Ear diameter (cm):
• Mean squares of locations (Loc.) were highly significant, while the man squares among genotypes (G), (C) and (C vs. Ch.) were significant to highly significant under the two locations and their combined. Partitioning of crosses, mean squares i.e. lines (L), testers (T) and lines x testers (L x T) analysis indicated that, the difference due to L, T and L x T were highly significant at the two locations and their combined data except for L x T was not significant.
• Three way crosses (Sk 5007/9 x SC-162, Sk 5009/12 x SC-162 and Sk 5019/17 x SC-162) increased but not significantly than the check TWC-353.
• Additive variance played an important role in the inheritance of these traits.
• Two inbred lines (Sk 5009/12) and (Sk 5019/17) had desirable significant to highly significant GCA effects at Sids location and the combined data, as well as the inbred line (Sk 5007/9) under Sakha location and the combined data.
8- Number of rows per ear:
• The mean squares due to locations (Loc.) were not significant. The mean squares among genotypes (G), (C), (Ch.) and, (C, vs. Ch.) were highly significant under the two locations and their combined. Differences among lines (L), testers (T) and lines x testers (L x T) were highly significant at the two locations and their combined data except for L x T was not significant.
• Three single crosses Sk 5002/4 x Sk-11, Sk 5007/9 x Sk-11 and Sk 5022/20 x Sk-11 increased but not significantly than the check SC-168.
• The additive variance played a major role than the non-additive genetic variance in the inheritance of these traits. Additive type of gene action was more influence by environment than non-additive gene action.
• With two parental lines (Sk 5002/4) and (Sk 5009/12) had desirable positive highly significant GCA effects for the two locations and their combined.
9- Number of kernels per row:
• Differences between the two locations (Loc.) were significant. Mean squares of genotypes (G), (C), (Ch.) and (C vs. Ch.) were significant to highly significant under the two locations and their combined data except for Ch. at the two locations. The mean squares due to lines (L), testers (T) and their interaction (L x T) were significant to highly significant under the two locations and their combined data.
• 14 three way crosses decreased but not significantly than the check TWC-353.
• The non-additive genetic variance played an important role in the inheritance these traits. Non-additive type of gene action was more influence by environment that additive gene action.
• The results revealed that the GCA effects had desirable positive and significant to highly significant values for the inbred lines (Sk 5008/10) toward higher number of kernels per row under the two location and their combined data, as well as the inbred line (Sk 5003/6) under Sids location and the combined data. The results cleared that the cross (Sk 5002/4 x Sc-162) had desirable significant SCA effects at Sakha and the combined.
10- Weight of 100 kernels (g):
• Mean squares due to locations (Loc.) were highly significant. The mean squares of genotypes (G) and (C) were highly significant. The mean squares due to lines (L), testers (T) and their interaction (L x T) were significant to highly significant under the two locations and their combined data.
• The combined data for weight of 100 kernels showed that one single cross Sk 5019/16 x Sk-11 increased significantly than the check SC-168.Also, three way cross (Sk 5018/15 x SC-162) increased significantly than the check TWC-353.
• The mean squares due to lines (L), testers (T) were highly significant under the two locations and their combined data except (T) at Sids location was not significant.
• The additive variance played a major role than the non-additive genetic variance in the inheritance of these traits. On another side, the magnitude of the K2GCA x Loc. interaction was higher than K2SCA x Loc.
• The results showed that three inbred lines (Sk 5009/12), (Sk 5018/15) and (Sk 5019/16) had desirable positive significant to highly significant GCA effects at the two locations and their combined data. Two crosses (Sk 5004/8 x comp-9 and Sk 5009/11 x Sk-11) had positive significant SCA effects at Sids location.
• (Sk 5019/16 x Sk-11), (Sk 5018/15 x Sk-11 and Sk 5018/15 x SC-162) and (Sk 5019/16 x Sk-11 and Sk 5018/15 x SC-162) at Sakha location, Sids location and combined data, respectively had significant superiority.
11- Grain yield (Ardabs/fed.):
• Mean squares due to genotypes (G), (C) and (C vs. Ch.) were highly significant. Differences among lines (L), testers (T) and lines x testers (L x T) were highly significant at the two locations and their combined data except (T) at sids location.
• The combined data for grain yield showed that one single cross (Sk 5009/12 x Sk-11) decreased but not significantly than the check SC-168. While, one three way cross (Sk 5004/7 x SC-162) increased but not significantly than the check TWC-353 in addition to, seven three way crosses decreased but not significantly than the check TWC-353.
• These results indicated that, the non-additive genetic variance played an important role in the inheritance this trait. The magnitude of the K2GCA x Loc. interaction was higher than K2SCA x Loc.
• Inbred line (Sk 5004/7) had desirable highly significant GCA effects at two locations and their combined data, while the inbred lines (Sk 5003/6) and (Sk 5007/9) had desirable significant to highly significant GCA effects at Sakha and the combined data. crosses (Sk 5002/4 x Sc-162 and Sk 5007/9 x Sc-162) (Sk 5009/11 x Comp-9, Sk 5009/12 x Sk-11 and Sk 5011/14 x Sc-162) and (Sk 5002/4 x Sc-162, Sk 5009/11 x Sk-11, Sk 5009/11 x comp-9 and Sk 5009/12 x Sk-11) had desirable significant SCA effects at Sakha, Sids and their combined, respectively.
• One three way cross (Sk 5003/6 x SC-162) at Sids location had significant superiority.