Mungbean germplasm comprising 262 accessions was evaluated for agro-morphological traits at National Agricultural Research Centre (NARC), Islamabad. Eighty selected accessions were included in biochemical (SDS-P AGE) analysis. In addition, genetic studies were conducted on eight mungbean genotypes in an 8x8 diallel cross.
High variance was observed for days to maturity, branches per plant, pods per plant, seeds per pod, grain yield per plant, biological yield per plant and harvest index. Grain yield per plant showed significantly positive correlation with branches per plant, pods per plant, biological yield per plant and harvest index. Negative association of biological yield with harvest index showed physiological inefficiency for appropriate partitioning of total dry matter towards economic yield, consequently the accessions with low grain yield attained low harvest index. The germplasm accessions were grouped into six clusters on average linkage basis. First three principal components (PCs) with eigenvalues>1 contributed 71.47% of the variability amongst the accessions. The populations with greater PC1 values were high yielding, late maturing and were characterized by high number of branches with more pods. The second component was strongly associated with earliness, more number of seeds and high harvest index. Green seed coat colour and shiny seed lustre proved their importance in selection for improving most of the yield contributing traits.
The SDS-PAGE conducted in various combinations revealed that 15% acrylamide gel concentration and 8 μl of sample quantity gave the best resolution. Out of 18 SDS-PAGE markers, 9 were polymorphic. The Protein peptide, 10a alone, revealed importance for detection of six important yield contributing characters, followed by bands, 2a and 7, each of which indicated its significance for four yield components. The association of biochemical variation with QTLs can be used for germplasm screening and further exploitation for mungbean improvement.
For gene action studies, data were analyzed following techniques viz. analysis of variance, combining ability analysis, genetic component analysis and Wr, Vr graphic analysis. Estimates of variances due to general combining ability (GCA) and specific combining ability (SCA) suggested predominance of additive gene action for plant height, days to maturity, pod length and 100 seed weight. High SCA variance for pods per plant, seeds per pod and grain yield per plant revealed the importance of non-additive gene action for these characters. The genotype, NM 51, was the best general combiner for pods per plant and grain yield per plant. The cross combination, NM 121-25 x VC 4152, was at the top for high grain yield on the basis of SCA. For the improvement of grain yield in mungbean, crosses involving the parents, NM-121-25, NM-51, VC-3902 and VC-4152, must be given special consideration.
The estimates of components of genetic variation (Hayman's approach) showed that additive genetic effects appeared to be important for plant height, days to maturity, pod length and 100 seed weight. The non-additive effects were more pronounced in the genetic control of pods per plant, seeds per pod and grain yield per plant. Directional dominance was observed for plant height, pods per plant, seeds per pod and grain yield per plant. The parents contained equal number of dominant genes for all the characters except 100 seed weight for which the genes were distributed asymmetrically among the parental lines. The graphic analysis revealed partial dominance for all the characters studied. Plant height, days to maturity, pod length and 100 seed weight being controlled by additive genetic effects with partial dominance will certainly provide the basis for selection in early segregating generations for improvement in these parameters.