![]() While T 2 was good combiner for grain yield and some of attributes. In addition, the T 1 as a tester was a GCA effects good combiner for earliness, shorter plants and lower ear placement traits. ![]() The L 1 and L 3 had the best general combiners for GY ard fed ⁻¹. The mean squares among two locations were highly significant for all studied traits except KR ⁻¹. During 2020 season, the resulted 30 crosses along with check hybrid SC-168 were evaluated in a yield trial at two locations: Gemmeiza and Sids Agric. Fifteen yellow maize inbred lines derived from different sources were crossed with two lines as tester i.e., Gm-1001 and Gm-1002 in 2019 summer season. This study was designed to estimate the magnitude of genetic parameters and heritability of traits in line × tester mating design. Understanding the genetic parameters and heritability of traits in every population is an essential precondition for selection program. The improvement of maize hybrids relies on significant genetic variability among the inbred lines used and the degree to which it is transferred to progeny. These crosses are valuable and could be used in maize breeding programs for high yielding ability Nine top crosses L2 ×T2, L2×T3, 元×T1, L4×T2, L5×T1, L6×T2, L8×T3, L9×T1and L10×T3 exhibited desirable SCA effects for grain yield and some of its components' traits. The inbred lines L1, 元, L6 and L10 exhibited positive and significant GCA effects for grain yield (ard/fed) and most of the other yield component traits. The inbred lines L8, 元 and L1 possessed the highest negative and significant GCA effects towards earliness, dwarfness and lower ear placement, respectively. While, only the top cross 元×T1 was significantly superior to the highest yielding check hybrid SC128. Four top crosses 元×T1, L6×T2, L1×T1 and L9×T1 were significantly out yielded the check hybrid TWC324. Moreover, the non-additive gene action was more affected by nitrogen levels than the additive gene action for all the studied traits except days to 50% silking. The non-additive genetic variance was greater than the additive genetic variance in governing the inheritance of all studied traits except number of rows/ear and grain yield (ard/fed). Significant interaction mean squares for C, L, T and L×T with nitrogen levels were detected for the most studied traits. Mean squares of crosses (C) and their partitioning lines (L), testers (T) and line × tester (L × T) interaction were highly significant for all the studied traits under the two nitrogen levels as well as for the combined data. ![]() Significant differences were noticed between the two nitrogen fertilizer levels for all the studied traits except ear diameter, indicating these traits were affected by nitrogen fertilizer levels. Thirty top crosses plus the two checks SC128 and TWC324 were evaluated in a randomized complete block design with three replications under two nitrogen fertilizer levels 80 and 120 kg N/fed in 2013 season. Ten white maize inbred lines and three testers SC10, SC122 and TWC310 were crossed in line × tester scheme in 2012 season. This study was conducted to estimate general (GCA) and specific (SCA) combining ability effects of some maize inbred lines for grain yield and other agronomic traits by using line × tester analysis under two nitrogen fertilizer levels.
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