TIR approach and stress tolerance indices to identify donor for high-temperature stress tolerance in pepper (Capsicum annuum L.)

Abstract

Bell pepper or sweet pepper (Capsicum annuum L. var. grossum) is highly susceptible to hightemperature stress (HT). Hence, search for donor across C. annuum for HT tolerance was undertaken by following Temperature Induction Response (TIR) technique. The induction and challenging temperature requirement for TIR screening were standardized in 1 d-old Capsicum seedlings. Forty Capsicum genotypes were evaluated based on the recovery growth (RG) and per cent reduction in recovery growth (%RRG) of the seedlings. The genotypes Punjab Guchhedar and Ajeet 1 were found to have maximum cellular level tolerance (CLT) to HT with higher RG and lower %RRG compared to the non-induced seedlings and HDC 75 was found to have minimum CLT. In order to confirm the findings, another experiment was conducted under managed stress and control conditions. Absolute yield obtained from both the environments were used to calculate stress tolerance indices such as heat susceptibility index, tolerance index, stress tolerance index, mean productivity, geometric mean productivity and yield stability index. Based on these tolerance indices, Punjab Guchhedar and Ajeet 1 were found to be highly tolerant andHDC75 as highly susceptible. Further, the combined result of TIR and tolerance indices also gave the same result confirming Punjab Guchhedar and Ajeet1 can be used as a donor for the future breeding programme aimed at evolving high-temperaturetolerant bell pepper cultivars. The result also confirms the fitness of TIR technique to screen Capsicum genotypes for tolerance to HT based on variability in acquired thermotolerance.