Screening of Castor Germplasm with High Photosynthetic Efficiency

Objective The research of photosynthetic characteristics of different castor germplasms was carried out to provide references for the selection and utilization of castor germplasms with high photosynthetic efficiency.

Method Based on principal component analysis and cluster analysis, a comprehensive evaluation of six photosynthetic parameters including intercellular CO₂ concentration (Ci), transpiration rate (Tr), stomatal conductance (Gs), net photosynthetic rate (Pn), leaf instantaneous water use efficiency (WUE) and transpiration efficiency (TE) of 29 castor germplasms from different regions were conducted to screen out excellent castor germplasm.

Result The variation coefficients of the six photosynthetic parameters ranged from 16% to 35%. Among them, Pn and Gs were the highest at 35%, and Ci was the lowest at 16%. Correlation analysis revealed that Pn significantly negatively correlated with Ci and significantly positively correlated with both Tr and WUE. The results of principal component analysis showed that three principal components could explain 99.15% of the six photosynthesis-related parameters.These components were photosynthetic factor, stomatal factor and moisture factor. Cluster analysis based on photosynthetic parameters divided the 29 castor germplasms into 4 groups, of which Group Ⅱ consisted of 4 materials (YSL-5, SD-21, A40-7, and B11-1), accounting for 13.79% of the total number of materials. These materials had the highest net photosynthetic rate, all exceeding the average net photosynthetic rate of the overall material, and the Pn, Gs and Tr in this group were all at a high level compared with those of other materials. Therefore, the four materials could be selected as castor germplasm with high photosynthetic efficiency suitable for breeding.

Conclusion The castor germplasm with high photosynthesis rate, large stomatal conductance and relatively high leaf instantaneous water use efficiency can be used as intermediate material for breeding of castor variety with high photosynthetic efficiency.