ABSTRACT
This chapter considers phenotypic differences in drought resistance in common bean genotypes and in classifying the genotypes as water spending or water saving plant ideotypes. The drought-resistant genotypes that are classified as the water savers ideotype presented lower values of grain carbon isotope discrimination and a negative relationship with both root vigor and grain yield. Thus, the water saver genotypes under drought stress generate fewer roots and therefore, use less water, resulting in reduced stomatal conductance and moderate gas exchange and plant growth. Genotypes with differential root system architecture should be used for the development of drought-resistant lines with improved root architecture for each specific agro-ecological condition. The genotypes classified as water spenders combined superior grain production under drought stress with a vigorous and deeper root system. Evaluations of root traits have shown the contribution of deep rooting to improved drought resistance through the greater acquisition of water.
