Dissecting the dependence of total biomass on physiological traits through path analysis

Water use efficiency (WUE) and total transpiration (T) are the two pivotal traits that determine the differences in total biomass (BM) accumulation. A significant genetic variability in these traits has been demonstrated in several crop species. Exploring of latter traits through breeding efforts to improve crop productivity have been rather slow in rice. To achieve success in crop improvement, it is important to understand the regulation of biomass accumulation by these physiological variables. Plant breeders often resort to the path analysis of the predictor variables and their influence on the response variables. Such analyses though have been extensively studied for yield attributing characteristics, very few studies have been conducted to understand the influence of the physiological traits such as WUE and T on biomass accumulation. Hence, a subset of random 40 Doubled Haploid Lines (DHLs) were examined in rice for the differences in WUE, T and BM. The statistical significance of path analysis indicated that WUE was controlled by the photosynthetic capacity, indicating that high WUE-DHLs would always have high biomass. This was further validated through a positive effect of mean transpiration rate on WUE through net assimilation rate. The outcomes of the current study suggest that the path analysis is a better approach to identify the genotypes with high WUE based on transpiration and photosynthetic rate.