Influence of drought stress on physiological traits of crossed okra varieties

Abstract

Drought and heat stresses are major constraints to agriculture worldwide, reducing crop productivity and affecting global food security. Two okra cultivars (Japanese and Egyptian) with different physiological attributes were crossbred for producing F1 hybrids. All cultivars and their hybrids were evaluated for drought stress tolerance at two water regimes (12% and 2%). At limited water condition, photosynthesis and stomatal conductance tended to decrease in Egyptian parent and Japanese ×Egyptian hybrid while transpiration rate showed no significant changes in both parents and F1 hybrids. Maximum quantum yield of PSII (Fv/Fm) ratio was decreased with decreasing soil moisture content in Japanese cultivar, E×J and J×E hybrids with mean value of (0.14, 0.16 and 0.15, respectively). Chlorophyll content in both parents and their hybrids was decreased under severe drought stress. Significant high activity levels of the anti-oxidative enzymes, peroxidase (POX) and superoxide dismutase (SOD) was observed in water-stressed plants than in well-watered (12% water regime) plants. The highest activity of POX was recorded in E×J hybrid (234.9 U/g FW) and the highest activity of SOD was found in Japanese cultivar (18.69 U/g FW). Accumulation of proline content under drought severity stress in both hybrids (E×J and J×E) was recorded (16.7 and 10.4 mg/g DW, respectively). The performance of E×J hybrid was more prominent than parents because of the strong antioxidant defence system and accumulation of higher proteins, proline and chlorophyll content than other cultivars.