Adaptation traits in dry bean cultivars grown under drought stress

drought is the major constraint to common bean (phaseolus vulgaris l.) production in mexico. the objective of this study was to identify physiological and phenological traits related to drought adaptation in common bean. a field experiment was conducted under a rainout shelter at the valley of mexico experimental station near texcoco, state of mexico. eight common bean cultivars from different genetic races and growth cycle and contrasted drought response were tested under drought stress and non-stress. irrigation was withheld 55 days after sowing at the initiation of flowering, to induce the stressed treatment. starting at this day, six consecutive nondestructive samplings were conducted at noon every other day. in each sampling, leaf water potential, stomata conductance and co2 assimilation rate were determined. data on phenology were also recorded. at physiological maturity, seed yield and shoot biomass were measured. harvest index was calculated. all cultivars exhibited a tendency to escape drought effects throughout accelerated reproductive development. this response was of small magnitude in mesoamerican cultivars negro cotaxtla 91 and bat 477 (type iii) and significant in cultivars from the durango race such as pinto zapata, bayo madero and bayo criollo del llano. significant difference among cultivars for stomata control was observed with high sensitivity in bat 477 and seq 12, cultivars from the mesoamerican race and in ica palmar from nueva granada race. bred and distinct cultivars ica palmar (type i) and pinto villa (type iii) from durango race, displayed high photosynthetic rate and harvest index, traits or mechanisms directly related to seed yield under stress and non-stress conditions.