Comparison and Cluster Analysis on Photosynthetic Characteristics and Water Usage Efficiency of Rice Germplasms

Photosynthetic characteristics (PC) of various rice germplasms were determined to identify high-efficient genetic resources for improvements on rice cultivars. In addition, the water usage efficiency (WUE) and chlorophyll content (SPAD) of 58 rice germplasms from various nations and regions were obtained for comparison and classification in a cluster analysis. The results showed that there were significant differences (P < 0.01) in photosynthesis rate (Pn), stomatal conductance (C), and transpiration rate (E), as well as highly significant differences (P < 0.05) in WUE, among the tested varieties. The 3 principal components cumulatively contributed to the variances among the cultivars at 85.31%on C, Pn and E being the 1^stprincipal component; on WUE and Pn, the 2^nd; and, on SPAD, the 3^rd. Based on Pn, WUE, and SPAD, the 58 germplasms were clustered into 7 groups. As a result, Group 1 and Group 6 consisting of 9 germplasms that showed high PC, WUE and SPAD were recommended for crossbreeding purposes.