Abstract
Four experiments were conducted during August, 2004 to April, 2008 to evaluate the QPM inbreds for yield, yield contributing and quality traits, to assess the variability, selection of prospective inbreds, estimate heterosis, nature of combining ability, gene action and identification of high productive desirable stable hybrids. The field experiments were conducted at Jamalpur, Jessore, Hathazari and Burirhat. Estimation of protein, lysine and tryptophan has been done in the laboratory of CIMMYT, Mexico. Twenty diverse inbreds were evaluated for the study. Six prospective and diversified inbreds were identified through selection and they were CML-162, CML-164, CML-170, CML-188, CML-191 and CML-193. High genotypic and phenotypic coefficients of variation were observed for plant height, ear height, cob length, cob girth, no. row/cob, no. seed/row, 100 seed weight, yield/plant, % poor husk cover, % protein, % tryptophan, % lysine and quality index. The maximum variation was estimated for % poor husk cover, plant height, ear height and grain yield/plant. Grain yield was positively correlated with all the traits except % poor husk cover, % protein, % lysine and % tryptophan. Using the selected inbreds as parents, crossing was made in a full diallel fashion. General combining ability variances were found lower than specific combining ability variances for plant height, ear height, days to pollen shedding, no. seeds/row, 100 seed weight and grain yield/plant indicating non-additive gene effects were more important for the inheritance of these traits. General combining ability effects revealed that the inbred CML-162, CML-170 and CML-193 were good general combiner for grain yield/plant. CML-188, CML-191 and CML-193 showed significant negative GCA effects for days to pollen shedding and days to silking which is desirable. CML-164, CML-170, CML-188 and CML-193 also showed significant positive GCA effects for cob length. Among the crosses CML- 162 x CML-191, CML-162 x CML-170, CML-164 x CML-191, CML-170 x CML-188, CML-170 x CML-193 and CML-191 x CML-193 showed maximum positive SCA effects for grain yield/plant,no.seeds/row,100 seed weight and no. rows/cob. The crosses CML-170 XCML-164, CML-193 XCML-162 and CML-191 xCML-162 exhibited significant and positive reciprocal effect for grain yield/plant. The crosses CML-162 x CML-191, CML-164 x CML-191 and CML- 191 x CML-162 revealed high heterosis over standard check variety and better parent for grain yield/plant. Twelve crosses were used to assess gene action. Scaling and joint scaling tests indicated the presence of non-allelic gene interaction for most of the traits in 12 crosses. Plant height, ear height and grain yield/plant were controlled by additive, dominance and additive x additive, additive x dominance types of digenic epistasis. The crosses CML-162 x CML-170, CML-162 x CML-191, CML-164 x CML-191, CML-170 x CML-188, CML-170 x CML-193, CML-191 x CML-162, CML-191 x CML-164 and CML-193 x CML-170 expressed complementary type of epistasis for yield and yield contributing characters and they could be used for development of hybrid variety. The hybrids CML-162 x CML-170, CML-162 x CML-191, CML-170 x CML-193, CML-193 x CML-162 and CML-193 x CML-170 were found to be stable for grain yield over different location. All the hybrids were stable for protein, lysine, and tryptophan content and quality index over environments. CML-162 x CML-191, CML-162 x CML-170 and CML-193 x CML-162 were high yielder but comparatively taller, while CML-193 x CML-170, CML-191 x CML-193 and CML-170 x CML-193 were dwarf and stout and grain yield was more than 9.0 ton/ha. The % poor husk cover was also observed minimum. Therefore, the hybrids CML-162 x CML-191, CML-162 x CML-170 and CML-193 x CML-162 are recommended for cultivation at early Rabi season in Bangladesh so that the crop may be harvested before strong wind of April-May. Based on the study, the hybrids CML-193 x CML-170, CML- 191 x CML-193 and CML-170 x CML-193 may be recommended for cultivation in the entire Rabi season in Bangladesh, because they were short and stout with stand against the environmental hazards.