Effect of drought stress on biochemical parameters in common bean, Phaseolus vulgaris L genotypes

Experiment was conducted to assess drought tolerance in two common bean genotypes by inducing stress at flower initiation stage on the basis of inherent stress tolerance characters viz total chlorophyll content, chlorophyll stability index, nitrate reductase activity and total free proline content. Foliar spray of salicylic acid (SA), boric acid (BA) and CoCl₂ was also applied to check whether they enhance drought tolerance by showing their impact on these parameters. Seeds of fifty common bean genotypes were evaluated for drought tolerance in the laboratory with two PEG-6000 osmotic potential levels (−0.3 MPa and-0.5 MPa). Less reduction in germination percentage was observed in KR 60 and KRC 5 genotypes. Pot trials revealed that drought stress at flower initiation stage significantly reduced total chlorophyll content, chlorophyll stability index, nitrate reductase activity whereas total free proline content activity and drought susceptibility index were significantly enhanced. Foliar application of BA, SA and CoCl₂ effectively ameliorated the negative effects of drought stress in both genotypes. Reduction in drought susceptibility index was also observed under these treatments as compared to stressed non-treated plants. SA 150 ppm and BA 0.1 per cent were found to be most effective and surpassed other treatments.