Differential response to water stress in two tropical common bean cultivars

Abstract

The common bean (Phaseolus vulgaris L.) yield comes from regions with some level of water deficiency. Maintaining crop yield under drought stress is thus one of the biggest challenges. In order to improve our understanding of the responses involved of common bean to drought stress, we studied photosynthesis, antioxidant system, photorespiration estimated by glycolate oxidase activity, and proline content in leaves of two common bean cultivars (Expedito and Macotaco) subjected to water stress induced by polyethylene glycol 6000. The stress imposed affected the two common bean cultivars by decreasing net photosynthesis rate and increasing glycolate oxidase (GO) activity due to stomatal closure. Increased flux of electrons through the photosystem II led to reactive oxygen species (ROS) production, as observed by increased hydrogen peroxide (H2O2) content and it enhanced the activity of the enzymatic antioxidant system such as superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and guayacol peroxidase (GPOD) in Macotaco. Both cultivars here studied showed similar effects on photosynthesis parameters, however, Expedito had a better response on antioxidant system and proline content, which may represent an advantage over Macotaco.