The effects of cold stress applied at different development periods of tomato on gene expression, morphological and physiological properties

Tomato, a plant of tropical origin, has long been a focus of scientific research regarding its responses to low temperature stress. Both cultivated tomatoes and their wild relatives exhibit a wide genetic variation in their responses to abiotic stress factors. Studies have explored the genetic mechanisms, key genes, and gene pathways involved in this variation, which have been further elucidated through their association with biochemical contents. Most of these studies have focused on the early seedling stage, examining gene expression from leaves. In this study, responses to low temperature stress were evaluated in both the early seedling and flowering stages, and the effects on fruit setting, fruit quality, seed yield, and germination in subsequent stages were analyzed. A total of 18 genotypes were tested, with biochemical analyses (MDA, H2O2), chlorophyll content measurements (SPAD502), and visual assessment criteria being used to compare genotypes. Principal component analysis and weighted rating methods were employed to select the three most sensitive and the three most tolerant genotypes, which were then exposed to +3°C low temperature for 7 days. The results revealed that genotypes tolerant to low temperature stress exhibited more stable gene expression levels and showed less variation in biochemical contents compared to sensitive genotypes. In the tolerant genotypes, fruit set rates were higher after the low temperature treatment during the flowering stage, and fruit deformities and seed losses were less frequent. Additionally, the germination rates of seeds from these genotypes were found to be higher. These findings suggest that genotypes showing high expression of genes such as the CBF gene family and LePOD could be included in breeding programs aimed at improving low temperature tolerance. The tolerant genotypes (R-5, R-6, and R-7) were confirmed to be more resilient to low temperature stress during the seedling and flowering stages compared to the control genotype (R-9), with the negative effects of low temperature on fruit development being less pronounced in these genotypes. These results provide valuable insights into the genetic mechanisms behind low temperature tolerance and serve as an important guide for the development of resistant varieties in tomato breeding.