Evaluation of drought and heat tolerance of common bean (Phaseolus vulgaris L.)

Abstract

The aim of this work was to evaluate drought and heat tolerance of different bean varieties (Phaseolus vulgaris. L) at two stages of development (vegetative and flowering) to understand the physiological aspects of drought tolerance between varieties. Local Egyptian bean varieties (Giza3 and Giza6) and varieties introduced to Egypt (Bronco, Flexo, and Tema) were subjected to water stress at seedling and flowering stages by withholding water for 6 days. The experiments were conducted in a well controlled greenhouse at the research station of the Institute for Vegetable Science at Durnast, Bavaria, Germany. Leaf water potential, stomatal conductance and chlorophyll content were measured during water stress in addition to yield measurements. Another group of plants from the same varieties were subjected to high temperature (32 °C) for 8 days but kept well-watered to avoid water stress. Photosynthetic rate and stomatal conductance were measured at the end of heat stress, Giza3 and Flexo varieties maintained higher leaf water potential, lower stomatal conductance during water stress and had higher yield than the other varieties. At the end of the heat stress period, Giza3 and Flexo had a higher photosynthetic rate and higher stomatal conductance which helped to maintain higher photosynthesis. The results indicate that Giza3 and Flexo varieties had relatively better control of stomata during water stress which allowed them to postpone the dehydration with consequently higher stability for heat stress.