Genetic Analysis for Desirable Attributes in Popcorn

Abstract

Quantification of genetic attributes including gene action, heterotic behavior, heritability estimates, phenotypic and genotypic associations are important statistical tools in progressive breeding programs. The genetic material includes eight diverse popcorn inbred lines in which four were selected on the basis of phenotypic variation. Two of the four parents were developed from indigenous popcorn material, while the other two were of exotic (Bangladesh). Parental inbred lines were crossed to get four F1 crosses. These F1 crosses were selfed to generate F2 and back crossed with their female and male parents to obtained, BC1 and BC2, respectively. In such way total genetic material synthesized in this study include four each of parents, F1s, F2s, BC1s and BC2s. These generations were evaluated at two locations i.e. Cereal Crops Research Institute (CCRI), Pirsabak, Nowshehra and The University of Agriculture (UOA), Peshawar. At both locations the experimental material was replicated thrice in randomized complete block design. Data recorded were analyzed using combined analysis of variance. Combined analysis of variance in all four crosses, revealed non-significant genotype × location interactions in days to tasseling, silking, anthesis, ear length, fresh ear weight, kernel rows ear-1, grains row-1, grains ear-1 and % unpopped grains, while rest traits exhibited significant genotype × location interactions in some crosses. Significant genotype × location interactions were observed for ear diameter in all crosses. Generation mean analysis indicated that in all crosses dominant gene action was predominantly important in the inheritance of both days to tasseling, anthesis and silking. The additive gene effect was found to be negative in these crosses but significant except PS-Pop-29-2-1 x BD- Pop-2-1-2 for anthesis. The digenic non-allelic epistasis of additive x dominance and dominance x dominance was considered the major contributing factor in the inheritance of days to anthesis in cross PS-1 x BD-2 and PS-2 x BD-2. Duplicate type of epistasis was observed in cross PS-1 × BD-1 for days to anthesis and silking, while complementary epistasis was observed in cross PS-1 x BD-2. Similarly, dominant gene actions were positive and significant in all crosses except, PS-2 × BD-1 (-9.16) for plant and ear height. Duplicate type of epistasis was observed for ear height in both cross PS-1 × BD-1 and PS-1 × BD-2, while in cross PS-2 × BD-1 and PS-2 × BD-2 complementary epistasis was found. On the basis of these results, it can be concluded that crosses in which additive gene effects were high, could be improved effectively in subsequent generations. For grain yield and related traits dominant gene action was positively significant in all crosses, indicating that the parental populations could be effectively utilized in hybrid development programs. Broad sense heritability estimates for all the studied characters varied from moderate to high level, while narrow sense heritability ranged from low to high in all crosses. Maximum broad sense heritability estimates for days to tasseling (0.76 and 0.76) and anthesis (0.84 and 0.83) were observed in crosses PS-1 × BD-2 and PS-2 × BD-2, respectively. Maximum narrow sense heritability estimates for days to anthesis (0.67 and 0.57) and silking (0.67 and 0.58) were observed in cross PS-1 × BD-2 and PS-2 × BD-2, respectively. High broad sense (0.82) and narrow sense (0.62) heritability estimates calculated for grain yield were observed in cross PS-2 × BD-1 and Cross PS-1 × BD-1, respectively. Grain yield related attributes exhibited high broad sense heritability, while narrow sense heritability estimates for these traits varied from moderate to high levels, which indicate greater contribution of the genetic portion in the inheritance. Quality parameter, expansion volume revealed maximum broad sense heritability of 0.76 and narrow sense heritability of 0.50 for cross PS-1 × BD-1 and PS-2 × BD-1, respectively. Heterotic levels both, mid parent and better parent were negative for flowering characters in all crosses. Maximum negative mid- and better parent heterosis of -7.15 and -3.77 for days to tasseling was observed in cross PS-1 × BD-1 and PS-2 × BD-1, respectively. In cross PS-2 × BD-1, maximum negative mid- and better parent heterosis were observed for days to anthesis (-6.74 and -3.65) and silking (-6.48 and -3.40). Heterotic levels both, mid parent and better parent were positive and high in magnitude for grain yield and all related attributes. Cross PS-1 × BD-2, exhibited maximum mid- (80.73) and better (62.74) heterotic values for grain yield. Maximum mid- and better parent heterotic values are indication of dominance gene actions in all four crosses. Genetic and phenotypic association of flowering characteristics with grain yield were negative in nature, while yield related attributes were positively correlated with grain yield. Grain yield was positively correlated with plant height, while negatively correlated with ear height in two crosses. Quality trait of expansion volume was negatively associated with grain yield. Based on our results, it would be wise to use those parents in hybrid crosses which exhibited both additive and dominant gene actions coupled with high narrow sense heritability estimates and having strong relationship along with high heterotic levels for most of the grain yield related traits. Although all the F1 hybrids were superior but the PS-2 x BD-2 was outstanding for grain yield. Therefore, this cross can be recommended for commercial cultivation. Both popping expansion and percent of unpopped grains was positively and significantly controlled by dominant genes in two of the four crosses, while in the other two crosses dominant gene actions were negative in nature.