Investigation of drought stress tolerance of different pepper (Capsicum annuum L.) varieties and the effect of polyamines on the improvement of the tolerance

In this study, drought stress tolerance of the pepper (Capsicum annuum L.) varieties Yükselince, Tural, Burdem and Varol was investigated for the first time using physiological and biochemical parameters. In addition, it was evaluated whether Putresin (PUT) and Spermin (SPM) polyamines contributed to the drought tolerance of four pepper varieties. After the dilution process, the pepper seedlings grown for 55 days in the plant growth cabinet were exposed to drought stress for 10 days after applying polyamine twice a day apart. At the end of this period, growth parameters, relative water content (RWC), total chlorophyll and carotenoid amounts, lipid peroxidation, proline content, antioxidant enzyme (Superoxide dismutase (SOD), Guaiacol peroxidase (GPX), Glutathione Reductase (GR) and Catalase (CAT)) activities and chlorophyll fluorescence parameters (PSII maximum quantum efficiency (Fv/Fm), PSII photochemical efficiency (ΦPSII), electron transfer rate (ETO), non-photochemical fluorescence quenching (NPQ) and photochemical quenching (qP)) ) were determined in seedlings pretreated and untreated with polyamine. It was determined that the growth parameters, RWC, total chlorophyll and carotenoid amounts decreased with the effect of drought stress, while the lipid peroxidation and proline amounts increased in all pepper varieties. It was found that the highest decrease in stem length by 17.68% and fresh weight by 44.75% was found in Burdem variety. The highest decrease in stem dry weight was observed in Varol variety by 44.79%. Although the highest decrease in total chlorophyll amount by 17.77% was found in Burdem variety, the amount of carotenoids decreased the most in Varol variety. The amount of malondialdehyde (MDA), which is an indicator of lipid peroxidation, increased the most in Burdem and Varol varieties with the effect of drought stress. The least increase in MDA amount and the maximum increase in proline amount were determined in Yükselince variety. Although the polyamine pretreatment varies according to the pepper variety used, it has a positive effect on the reductions in growth parameters, RWC, total chlorophyll and carotenoid amounts, and on the decrease in the amounts of MDA and proline. Antioxidant enzyme activities increased in all pepper varieties under the influence of drought stress. The increase in GPX and GR activities was higher in Yükselince compared to Burdem and Varol varieties. SOD and CAT activities were mostly detected in Varol variety. PUT and SPM pretreatment had an effect on increasing the activity of antioxidant enzymes in general. Fv/Fm, ΦPSII, ETO and qP values decreased, while NPQ values increased with the effect of drought stress. The highest decrease in Fv/Fm, ΦPSII, ETO and qP values and the highest increase in NPQ values were detected in Burdem and Varol varieties. It was determined that the polyamine pretreatment had a general enhancing effect on the photosynthetic efficiency, different from the pepper varieties used in the study. According to the findings, it was concluded that Yükselince variety was the most tolerant to drought stress, Burdem and Varol varieties were more sensitive. In addition, it can be said that polyamine pretreatment has a positive effect on the negative effects of drought stress and improves drought tolerance in pepper varieties.