A QTL-Based Model for Node Addition Rate in Recombinant Inbred Lines of the Common Bean.

Ecophysiological model for predicting the node addition rate was developed for a family of recombinant inbred lines (RILs) of the common bean (Phaseolus vulgaris L.). The parameters in the model, base temperature (T_base), first optimum temperature (T_opt1), and N_m (maximum node addition rate) were estimated across five sites for each RIL. The average T_base and T_opt1 of all the 141 RILs were estimated as 10.0 ± 3.0 °C and 22.3 ± 4.0 °C, respectively. The average N_m was 0.25 ± 0.04 node/physiological day (node PD^-1) and 0.31 ± 0.05 node PD^-1 for determinate and indeterminate plants, respectively. Parameters in the model for node addition rate were then linked to quantitative trait loci (QTL). The QTL analysis of model parameters showed several QTL for N_m (six loci), T_base (three loci) and T_opt1 (four loci), respectively. The fin (PvTFL1Y) gene was responsible for 33% of phenotypic variation in N_m. The QTL model for N_m (one-parameter, QTL-based model) was able to mimic the important site-dependent QTL and captured the temperature responses under site-specific environments. Thus, the identified QTL were incorporated into corresponding model parameters, building the three-parameter, QTL-based ecophysiological model. The one-parameter and three-parameter QTL-based models were evaluated using independent data and showed good prediction of node addition rate (RMSE =0.05, d-statistic=0.63). The model was also tested with different genotypes and showed adequate prediction of the nodes on main stem, with RMSE ranging within one node across genotypes.