Genotypic and Phenotypic Correlation Analysis for Seed Yield and Its Component Traits among 100 Indigenous and Exotic Accessions of Pigeon Pea [Cajanus cajan (L.) Mill sp.]

Abstract

Pigeonpea [Cajanus cajan (L.) Millsp.] is the second most important grain legume in India, and improvement of seed yield remains the principal objective of most breeding programmes for the crop. Because yield is a complex, polygenically controlled character that is strongly modulated by the environment, an understanding of the magnitude and direction of its association with component traits is essential for framing an efficient, biologically meaningful selection index. In the present investigation, a genetically diverse panel of 100 indigenous and exotic pigeonpea accessions, assembled from the National Bureau of Plant Genetic Resources, New Delhi, and the All India Coordinated Research Project on Pigeonpea, was evaluated in 2023 at three locations in Chhattisgarh, India, namely Raipur, Bhatapara and Kawardha, representing red-yellow, laterite and black soil types, respectively. Genotypic (rg) and phenotypic (rp) correlation coefficients were computed for twelve quantitative traits, viz., plant height, primary branches per plant, pods per plant, pod length, seeds per pod, days to first flowering, days to 50% flowering, days to maturity, 100-seed weight, pods per cluster, seed yield per plot and seed yield per plant, following the standard biometrical procedure of Singh and Chaudhary (1979). Seed yield per plant exhibited strong, positive and highly significant associations at both genotypic and phenotypic levels with seed yield per plot (rg = 0.933), seeds per pod (rg = 0.862), pods per plant (rg = 0.802), 100-seed weight (rg = 0.766) and pods per cluster (rg = 0.763), whereas days to maturity (rg = -0.490) and days to 50% flowering (rg = -0.457) showed significant negative associations. Genotypic correlation coefficients exceeded their corresponding phenotypic values for almost every trait pair, pointing to a strong inherent genetic association that is partially masked at the phenotypic level by environmental effects. A correlation heat map and a force-directed trait-association network constructed from the genotypic correlation matrix consistently identified pods per plant, seeds per pod, 100-seed weight and pods per cluster as the principal hub traits directly linked to seed yield, while the flowering- and maturity-related traits formed a distinct, negatively associated module. These findings suggest that simultaneous selection for pods per plant, seeds per pod and 100-seed weight, combined with moderate earliness, may provide a useful strategy for achieving genetic improvement of seed yield in pigeonpea.