COMBINING ABILITY FOR GRAIN YIELD AND SOME RELATED TRAITS OF NEWLY YELLOW MAIZE (Zea mays L.) INBRED LINES

Nine S 5 newly yellow maize inbred lines were developed from segregated generation of different Hungarian sources were topcrossed with two testers i.e., inbred line Giza (Gz)-656 and single cross SC-166 at Ismailia Agricultural Research Station during 2009 growing season. In 2010 summer season, the 18 topcrosses and two yellow commercial check hybrids; SC-162 and TWC-352 were evaluated on two locations; Sakha and Ismailia Agricultural Research Stations. The studied traits were grain yield (GY ard/fed), ear length (EL cm), ear diameter (ED cm), No. of rows ear -1 (RE -1 ), days to 50% silking (SD day) and plant height (PH cm). Results showed that the differences between two locations were significant for all studied traits, indicating that environmental conditions were different at both locations. The crosses and their partionining to lines were significant for all studied traits except RE -1 trait for lines. Mean squares due to (L x Loc) were significant for RE -1 , SD and PH traits. On the other hand, the interaction of (T x Loc) and (L x T x Loc) were insignificant for all studied traits except GY and PH traits for (L x T x Loc) interaction which were significant. The topcrosses (L 1 x T 1 ) (36.37 ard/fed), (L 2 x T 1 ) (36.80 ard/fed) were significantly out yielded the check hybrid SC-162 (32.40 ard/fed). Meanwhile, the topcrosses L 1 x T 1 (36.37 a ard/fed), L 2 x T 1 (36.80 ard/fed), L 7 x T 1 (35.53 ard/fed), L 2 x T 2 (34.32 ard/fed) and L 7 x T 2 (33.50 ard/fed) were highly significant compared with the check hybrid TWC-352 (30.20 ard/fed). The inbred lines L 1 , L 2 and L 7 have desirable GCA effects for GY and some yield components. Also, the inbred lines L 3 and L 8 exhibited desirable negative GCA effects for earliness and shorter plants. The relative relationship between GY GCA effects and the yield component traits (YCTs) GCA effects suggested that the direction of grain yield GCA effects (i.e., positive or negative) was largely determined by the number of YCTs GCA effects in the same direction. That is, if a line had significantly positive GY GCA effects, it usually had more YCTs with significantly positive GCA effects, and if as line had significantly negative GY GCA effect, it generally had a greater number of YCT significantly negative GCA effects. The additive genetic effects ( σ 2 GCA) seemed to have played an important role than non additive genetic effects ( σ 2 SCA) in the expression of grain yield, ear length, ear diameter and silking date traits, while the σ 2 SCA played the major role in the inheritance of No. of rows ear -1 and plant height traits. most of these traits. The contribution values were (80.58%) for GY, (63.04%) for EL, (87.62%) for ED, (84.38%) for RE -1 , (88.49%) for SD and (66.90%) for PH. The contribution of testers and (L x T) was low for all studied traits. These results are in agreement with those obtained by Aly (2004) and Aly and Mousa (2008). The additive genetic effects ( σ 2 GCA) seemed to have played an important role than non additive genetic effects ( σ 2 SCA) in the expression of GY, EL, ED and SD traits, while the σ 2 SCA played the major role in the inheritance of RE - 1 and PH traits. This result supports the finding of Nawar and El-Hosary (1984) for ED and RE -1 , El-Shenawy (2005) for GY and Mosa (2010) for EL, ED and RE -1 . From the same table, results revealed that the variance interaction of σ 2 GCA L x Loc was higher than σ 2 GCA T x Loc for GY, RE -1 , SD and PH, indicating that the σ 2 GCA for lines was affected more by environmental than by testers for these traits. Results showed that the σ 2 SCA x Loc were more than those of σ 2 GCA x Loc for all studied traits except RE -1 trait. Similar results were reported by Mosa (2010) for GY, ED and SD traits.