EVALUATION OF SOME WHITE MAIZE INBRED LINES FOR COMBINING ABILITY BASED ON TOP-CROSSES

Abstract

Nine white maize inbred lines i.e., Gm 305, Gm 309, Gm 310, Gm 315, Gm 316, Gm 317, Gm 318, Gm 319 and Gm 320 were developed at Gemmeiza (Gm) Agricultural Research Station and top-crossed with three inbred line testers i.e., Gm 30, Sd 7 and Sd 63 during 2006 summer season at Gemmeiza Station. Twenty seven top crosses and three commercial checks single crosses 10, 122 and 129 were evaluated in replicated field trials at Gemmeiza and Sakha Agricultural Research Station, Agriculture Research Center (ARC), Egypt during 2007 summer season. Mean performance, General (GCA) and Specific (SCA) combining abilities as well as proportion association of all inbred lines and testers lines and their interaction were estimated for, days to 50% silking, plant and ear heights, ear kernels number of per, 100-kernel weight and grain yield characters. The obtained results showed; highly significant differences among lines, testers and lines x testers for most of the studied traits. Highly significant differences were found between locations, locations x lines and locations x testers. Some of promising lines showed significantly positive GCA effects under both locations. Tester inbred line Sd 7 was found to be the best general combiner for high yielding ability followed by Gm 30 inbred line. However, the tested inbred lines Gm 319, Gm 305, Gm 309 and Gm 320 were significantly and respectively better general combiner for grain yield ability. The top cross Gm 320 x Sd 7 was significantly better than the commercial S.C.10 by (4.27 ard/fed). However, seven top crosses i.e., Gm 318 x Sd 7, Gm 309 x Sd 7, Gm 318 x Gm 30, Gm 310 x Sd 7, Gm 310 x Sd 63, Gm 316 x Sd 7 and Gm 305 x Sd 63 were significantly better than the control single crosses 122 (30.02 ard/fed), 129 (29.26 ard/fed) with productivity of 37.08, 36.90, 36.83, 36.28, 35.88 and 34.40 ard/faddan, respectively with significant positive SCA effects for grain yield. Therefore, these eight crosses should be going to advanced testing steps for releasing as new white single crosses.