Principal Component Analysis of Morphometric Traits in Induced Mutants of Mungbean [Vigna radiata (L.) Wilczek]
Deepshikha Saikia *
Department of Plant Breeding & Genetics, Assam Agricultural University, Jorhat-13, India.
Akashi Sarma
Department of Plant Breeding & Genetics, Assam Agricultural University, Jorhat-13, India.
Saibal Ray
Department of Plant Breeding & Genetics, Assam Agricultural University, Jorhat-13, India.
*Author to whom correspondence should be addressed.
Abstract
Aims: To characterise morphometric variation among mungbean mutants and other genotypes in two successive mutant generations (M4 and M5) using principal component analysis (PCA).
Study Design: A randomised block design with three replications.
Place and Duration of Study: Instructional-cum-Research Farm, College of Agriculture, Assam Agricultural University, Jorhat, Assam, India, during the kharif season of 2018 and the summer season of 2019.
Methodology: Thirteen genotypes were evaluated: six mutant lines (three synchronous-maturity, one dense-clustered, one long-podded and one brown-podded) selected from the cultivar Pratap (SG-1) treated with gamma rays and ethyl methanesulphonate, five Bhabha Atomic Research Centre (BARC) genotypes and two controls. Twelve traits were recorded: days to 50% flowering, days to pod initiation and days to maturity, plant height, branches per plant, clusters per plant, pods per cluster, seeds per pod, disease infection, pod length, 100-seed weight and seed yield. PCA was performed on genotype means for M4, M5 and the pooled generations, retaining principal components (PCs) with eigenvalues above 1.
Results: Four PCs explained 80.49% of the variation in M4 and five PCs explained 80.09% in M5. In M4, PC1 (42.57%) was a yield and pod axis (seed yield 0.94, seeds per pod 0.91, pod length 0.88). In M5, PC1 (24.90%) was a maturity and seed-size axis (days to maturity 0.83, 100-seed weight 0.78). In the pooled analysis, PC1 (35.46%) separated the two generations, whereas PC2 (18.90%), defined by seed yield, pod length and 100-seed weight, was shared across both generations. The long-podded and brown-podded mutants had the highest PC1 scores in both generations (M4: 3.88 and 3.94; M5: 3.76 and 2.18).
Conclusion: Trait associations depended on the generation. The long-podded and brown-podded mutants were the most consistent genotypes for pod and seed traits and merit evaluation over more seasons and locations, as generation and season were confounded.
Keywords: Mungbean, induced mutants, principal component analysis, morphometric traits, gamma rays, EMS