Drought and salt stress effects on biochemical changes and gene expression of photosystem II and catalase genes in selected onion cultivars

Onion is the main condiment vegetable crop that is grown and consumed due to its rich nutraceutical properties. Globally, drought and salt stress are the major hurdles for onion growth and pose greater threat to the future crop growth. Numerous studies reported the response of vegetable crops with the acclimatization to fluctuating environmental conditions but data for onion appears to be limited on biochemical and gene expression changes. In this study, we investigated the response of seven onion cultivars from Turkey for biochemical and gene expression responses to drought and salt stresses under greenhouse conditions. There is limited data available on NCBI for onion genes; therefore, degenerate PCR approach was used to amplify the catalase (CAT) and photosystem (PSII) genes of onion to observe correlation between their activity with transcript levels. Results of biochemical attributes indicated that the cultivars Perama, Inci, and Seyhan performed better compared to other cultivars with the exposure to salt and drought stress. Additionally, these cultivars also accumulated higher transcript level of CAT gene and showed least decrease in the degradation of PSII mRNA. Overall, results revealed that the cultivars Perama, Inci, and Seyhan were tolerant, whereas the cultivars Elit and Hazar were grouped as sensitive to salt and drought stress conditions. Results of this study can be used for screening of tolerant and susceptible cultivars. Moreover, the tolerant cultivars Perama, Inci, and Seyhan can be used for future abiotic stress breeding programs.