Thermal stress-induced physiological and biochemical alterations in papaya genotypes

Low-temperature stress significantly affects physiological processes inducing plant growth hindrance,and reducing crop productivity. The present study aimed to understand the low-temperature stress inducedphysio-chemical behaviour of five papaya genotypes (Pusa Nanha, Red Lady, P-9-5, P-7-9 and one wild relativespecies Vasconcellea cundinamarcensis). Low temperature stress significantly decreased the canopy gasexchange parameters, relative water content (RWC), membrane stability index (MSI) and chlorophyll contentin all the papaya genotypes, while tending to increase the total soluble sugars, proline and total solubleproteins, although the alterations were genotype-specific. V. cundinamarcensis showed greater tolerance tolow-temperature stress followed by P-9-5 and P-7-9 than other genotypes by maintaining the highest RWC,MSI, total soluble proteins, chlorophyll and proline contents. Our results showed that the chlorophyll content,membrane lipid peroxidation and MSI could be used as the indices for the screening of potential papayagenotypes against cold tolerance.