Comprehensive Evaluation of 37 Long-podded Cowpea Germplasm Resources Based on Grey Relational Analysis and Principal Component and Cluster Analysis

Objective The research was performed in order to have a full utilization of the long-podded cowpea germplasm resources.

Method 11 agronomic traits of 37 germplasm resources of long-podded cowpea were tested with the methods of principle component analysis, cluster analysis and grey relational analysis.

Result Among the 37 germplasm resources of long-podded cowpea, the coefficient of variation of agronomic traits ranged from 7.99% to 42.02%. The coefficient of variation of pod length and pod width was the smallest (< 10%), and these traits showed the highest stability. Thus, the breeding of long-podded cowpea could be focused on screening and improving other 9 agronomic traits that had relatively high coefficient of variation (> 10%). These agronomic traits could be transferred into 6 principle components and the accumulative contribution rate of the first 6 components was 87.17%, thus they could be used to replace the 11 agronomic traits for evaluation and breeding of 37 germplasm resources of long-podded cowpea. When genetic distance degree was 10, 37 germplasm resources of long-podded cowpea cultivars could be divided into 3 cluster types: 28 cultivars were divided into type Ⅰ; 5 cultivars were divided into type Ⅱ; 4 cultivars-Heshun, Nanbin708-K, Hongfeng 708 and Hanmei No.8 belonging to type Ⅲ had relatively high yield and better quality, which were suitable for the planting and promotion of long-podded cowpea in Hainan. According to the weighted grey relational analysis, the cultivar Heshun, which had the highest weighted correlation of 0.7285, was the best for planting in Hainan. The principle component analysis and weighted grey relational analysis showed consistent result when comparing agronomic traits of 37 long-podded cowpea cultivars.

Conclusion Through principle component analysis and weighted grey relational analysis, 10 germplasm resources of long-podded cowpea with better quality were obtained, respectively. Comparing these germplasm resources, 6 of them (Heshun, Ruixianggui, Nanbin 708-K, Jiangjun 708, Hanmei No. 7 and Hanmei No. 8) are in common. This indicate that both methods can be used for screening and evaluation of germplasm resources.