Low-temperature modified DNA methylation level, genome template stability, enzyme activity, and proline content in pepper (Capsicum annuum L.) genotypes

Low-temperature stress has a significant effect on plant physiology, inducing growth hindrance and reducing yields. This study aimed to explore the effect of low-temperature stress [control (20/15 °C), 15/12 °C (LT1) and 10/8 °C (LT2) during day/night] on plant growth, enzyme activities, proline and H₂O₂ content, DNA methylation, and genome template stability (GTS) as well as chlorophyll content in pepper cultivars (AK, KD, YC, and TK). Based on the results, low-temperature stress significantly decreased the plant dry biomass, CAT activity, and chlorophyll content in pepper cultivars but had a slight impact on AK cultivar. The highest proline content (46%) was detected in the AK cultivar under LT1 compared to the control, but its lowest content (18.9%) was observed in the TK cultivar. Furthermore, the lowest and the highest hydrogen peroxide content under LT1 were found in the AK and TK cultivars (8.5% and 13.0%, respectively) compared to the control. Based on the results, low-temperature stress decreased GTS in all cultivars, but the highest GTS rate was observed in the AK cultivar, and this was paralleled by having the highest plant dry biomass, enzyme activity, and proline content compared to the other cultivars. Low-temperature stress increased the DNA full methylation ratio in all pepper cultivars, whereas the AK cultivar was less affected compared to the other cultivars. These results suggest that pepper cultivars' responses differ under low-temperature stress, and the AK cultivar showed greater tolerance to low-temperature stress compared to the other cultivars by having the highest GTS, POD, and CAT activities, as well as chlorophyll and proline content. Furthermore, proline was more effective compared to antioxidant enzyme activities in countering the harmful effects of cold stress in pepper.