Phenotypic diversity in the pigeonpea (Cajanus cajan) core collection

The pigeonpea core collection developed at ICRISAT genebank consists of 1,290 accessions from 53 countries. The core collection, which includes selected lines in extra early, early, medium and late maturity groups was evaluated for 18 qualitative and 16 quantitative characters during the 2004 rainy season, to assess the phenotypic diversity and determine the relative importance of different characters in evaluating pigeonpea germplasm accessions. The four maturity groups differed significantly for all characters under study. The medium maturity group showed significantly higher mean number of primary, secondary and tertiary branches, number of racemes, pod bearing length, pods per plant, shelling percent and plot seed yield. Late maturity group showed significantly higher mean for leaf size, plant height, pod length, seeds per pod and 100-seed weight, indicating this group as a good source of vegetable pigeonpea. Significant positive correlations were found between number of secondary branches and pods per plant in extra early group ( r = 0.756), late maturity group r = 0.776) and entire core ( r = 0.728) and between number of racemes and pods per plant in all maturity groups and entire core. Principal coordinate and principal component analysis showed that seven qualitative and nine quantitative traits were important in explaining multivariate polymorphism. The Shannon-Weaver diversity index ( H') varied for different maturity groups and traits. Phenotypic diversity, averaged over all the 16 characters, increases from extra early group ( 0.36 +/- 0.04) to late maturity group ( 0.42 +/- 0.04) suggesting that medium and late maturity groups have greater diversity compared to extra early and early maturity groups.