Relative Effect of Root and Shoot Genotypes on Yield of Common Bean under Drought Stress

Abstract

The inherent interactions of roots and shoots make it difficult to determine whether a characteristic such as response to drought is under control of genes expressed in roots, shoots, or throughout the plant. One approach for obtaining such information is to interchange root and shoot genotypes through grafting. In this study, plants of common bean (Phaseolus vulgaris L.) were cleft grafted and then transplanted to the field to evaluate their yield response under drought. Anticipating that the importance of root or shoot genotype would vary with genotypes evaluated, variation in rainfall patterns, and soil conditions, four yield trials with varying sets of genotypes were conducted at two sites with highly contrasting soils. At Palmira, Colombia, the soil was a fertile Mollisol (Aquic Hapludoll, pH = 7.7), and at Quilichao, Colombia, an Oxisol (Plinthic Kandiudox, pH = 5.0), where problem of low pH and high Al saturation were expected to adversely affect root growth. In all trials, root genotype had a significant and usually large effect on seed yield, while shoot genotype had no effect. No root and shoot genotype interaction occurred, and an effect of grafting was only detected in one trial. These results suggest that root characteristics are of primary importance in determining drought response of common bean and, conversely, that shoot characteristics are of much less importance. However, response of specific genotypes varies greatly with environment.