Morpho-Physiological Response to Heat Stress During Seedling Stage and Interrelation With Agronomical Traits in Pepper (Capsicum Annuum L.) Cultivars Differing in Heat Tolerance
Identification of heat tolerance trait in pepper genotypes is an important for the breeding of heat tolerant cultivars in pepper. Therefore, in the present study were investigated effect of heat treatment (HT) on morpho-physiological and biochemical status of two commercial pepper cultivars "Chyung Yang" and "New Bigarim" in seedling stage and their post-treatment reproductive ability. The seedlings with 8-10 true leaf stage were maintained at day and night temperature of 42°C for 10 days and
... C for 10 days and cv. "Chyung Yang" were identified as a heat tolerant and "New Bigarim" as a susceptible to heat stress. The HT survival were revealed during 5 days and the threshold of heat tolerance were determined within 10 days of treatment among cultivars. We found no significant relation between leaf heat damage levels (LHD) with chlorophyll content (CHL). During HT were identified significant reducing of the biomass of seedlings, whereas the photosynthetic rate (PN), intercellular CO2 concentration (Ci), stomatal conductance (Gs) and transpiration rate (Tr) values were increased than in normal treatment (NT) seedlings. The cell membrane thermostability values were not steady during HT and in heat treated seedlings at recovery stages, where electrical conductivity (EC) rate showed of the increasing in seedlings at HT than NT. Total free proline content (PRL) significantly increased in HT stressed seedlings over NT on day 5 of treatment, when survival of seedlings were finished. In both cultivar plants with different LHD were identified the significantly increasing of PRL than NT plants at recovery, where the mean fold increase within 2-3 times than in seedlings which were exposed to the HT. LHD significantly effected on reproductive growth stage, where LHD levels over 25% was critical for plants recovery. There no identified the any significant the linkage of heat tolerance in seedling stage with reproductive growth stage, where cv. "Chyung Yang" was determined as a heat tolerant in seedling stage but in reproductive stage it showed negative index of agronomical traits.