Insights from morpho-physio-biochemical and molecular traits of hot pepper genotypes contrasting for heat tolerance

The present study compared the morpho-physiological, biochemical, and molecular responses of heattolerant (DLS-161-1) and heat-susceptible (DchBL-240) genotypes of hot pepper under high-temperature conditions. The results showed that DLS-161-1 performed significantly better for various morphological parameters such as plant height (60 cm), number of fruits per plant (180.33), average fruit length (8.40 cm) and leaf parameters. While DChBL-240 has significantly higher malformed seeds per fruit (15.06) and average fruit diameter (12.56 cm). The physiological responses also differed significantly between the two genotypes, with the DLS-161-1 exhibiting higher membrane stability index (65.99%), pollen viability (92.10%), photosynthetic rate (20.73 μmol CO2 m²/sec.), stomatal conductance (0.31 mol H2O m²/sec.), and transpiration rate (8.85 mmol H2O m²/sec). Biochemical analysis revealed significantly increased activity of antioxidant enzymes such as guaiacol peroxidase (564.99 U/g F.W) and catalase (711.90 U/g FW), increased protein content (13.38 mg/g F.W) and reduced malondialdehyde generation (13.42 nmol g-1 FW) in DLS-161-1 compared to heat susceptible genotype (DChBL-240). Further, two of the six heat shock protein genes, CaHSP2271 and CaHSP3, were highly upregulated in the DLS 161-1. The observations suggest that DLS-161-1 could adapt to high-temperature conditions by regulating its morphological, physiological, biochemical and molecular mechanisms.