Brassinosteroids or proline can alleviate yield inhibition under salt stress via modulating physio-biochemical activities and antioxidant systems in snap bean

Legumes are sensitive to salt stress, especially in the early phases of growth. Brassinosteroids (BRs) or proline (Pro) have been shown to improve salt stress tolerance in several plant species when given exogenously. Therefore, two pot experiments laid out in 4 x 3 factorial in a completely randomised design, replicated three times were carried out on snap bean (Phaseolus vulgaris L.) cv. Valentino to examine the roles of BRs or Pro in improving the salt tolerance of snap beans. The first factor included four saline irrigation water levels viz. 0.0, 20, 40, and 60 mM sodium chloride (NaCl), while the second factor involved foliar application with 0.1 mu M BRs or 30 mM Pro or distilled water as control. The results revealed that saline irrigation water reduced chlorophyll, membrane stability, relative water content, and yield. Exogenous BRs or Pro alleviated salt stress by reducing uptake and translocation of Na+ and Cl- while enhancing plant K+ assimilation. Increased water status, chlorophyll content, and antioxidant enzyme activity (SOD, POD, CAT) in leaves of snap beans may contribute to improved salt tolerance. These findings suggested that foliar treatment of brassinosteroids or proline could be an effective strategy to improve snap bean salt tolerance.