Investigation of drought tolerance response in some rice (Oryza sativa L.) cultivars

This study was carried out in consideration of the importance of rice (Oryza sativa L.) and the negative effect of drought on the plants. In this study, rice varieties (Osmancık-97, Beşer, Paşalı, Gönen, Halilbey, Kızıltan, Karacadağ, Hazro) were exposed to drought stress applications for 3, 6, 9, and 12 day duration and some morphological, physiological and biochemical responses have been investigated. According to the responses to the drought stress factor, the relationship between varieties and their tolerance-sensitivity degrees was investigated. In the first stage, at the end of drought applications (3, 6, 9 and 12 days), the measurements and analyses were carried out for the root-shoot height, fresh-dry weight, 0-5 visual scale evaluation, relative water content, pigment content, osmotic potential and amount of malondialdehyde (MDA) which is the final product of lipid peroxidation. The percentage changes in the varieties exposed to drought stress were calculated according to control groups. Moreover, it was determined that fresh weight, relative water content, osmotic potential and chlorophyll-a contents decreased in all varieties while plant height and dry weight values varied according to varieties. On the other hand, chlorophyll b, carotenoid and MDA levels increased in all varieties as well as increase of root height. When all the parameters were evaluated in overall, Osmancık-97 and Beşer varieties, which gave different responses to the drought stress factor, was evaluated as tolerant, Halilbey ve Karacadağ varieties as sensitive. In the second stage, in tolerant and sensitive rice varieties, proline, total soluble carbohydrate, hydrogen peroxide (H2O2), total soluble protein, abscisic acid (ABA), indole acetic acid (IAA), zeatin riboside (ZR) content and catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), superoxide dismutase (SOD) activities were investigated. Total amount of soluble protein, CAT, APX, GR enzyme activities have differed according to the varieties and stress application period. As a result, the amounts of proline, total carbohydrate and H2O2 in Osmancık-97 and Beşer (tolerant) varieties were found to be lower than Gönen and Karacadağ (sensitive) varieties also antioxidant enzyme activities and ABA content has found to be higher in tolerant varieties. Therefore, these varieties are evaluated more tolerant to drought stress compare to other varieties. In this study were obtained significant scientific data on how to produce resistant some rice varieties to stress conditions and lack of basic information were closed on the degree of impact from drought some rice varieties grown in our country. Also this study will contribute to the country's economy and will provide a basis for further research.