Association of nodule performance traits with shoot performance traits of common bean under drought stress

Abstract

The effect of drought stress on the association of nodule performance traits with shoot performance traits was studied using six common bean lines with contrasting differences in their adaptation to drought and low phosphorus (P) availability in soil. Drought stress reduced leaf water potential and gas exchange characteristics (CO2 assimilation, stomatal conductance) in all lines tested but two drought-tolerant lines, BAT 477 and BT_34-1,-1 were superior in their ability to adjust their leaf water status under drought. These two lines were also superior in root growth, rate of CO2 assimilation, vegetative biomass production, and nitrogen fixing ability under drought stress. A direct relation between symbiotic nitrogen fixation and nodule fresh weight with gas exchange traits as well as biomass production existed suggesting that relative growth of shoot vs. root depends on the provision of nitrogen by symbiotic nitrogen fixation and photosynthetic carbon assimilation. Overall, differences found in nodule, root and shoot performance traits indicated that the P-efficient bean line (BT_34-1-1) was superior than the other lines in terms of adaptation to drought. Results showed marked association of nodule performance traits with shoot performance traits under drought stress. We suggest that nodule characteristics and SNF ability should be included with above and below ground traits as phenotypic markers in germplasm evaluation and breeding programs that are aiming for improving drought tolerance in common bean.