CHARACTERIZATION OF DROUGHT TOLERANCE TRAITS IN SELECTED RICE (Oriza sativa L.) GENOTYPES GROWN IN SUDAN USING SIMPLE SEQUENCE REPEAT (SSR) MARKERS

Abstract

Rice (Oryza sativa L.) is one of the most important staple food crops providing the world’s nutritional energy and 20% nutritional protein. It is cultivated under diverse ecological conditions ranging. Rice growth and productivity are unfavourably affected by various biotic and abiotic stresses; key among them being drought. Drought is the most important limiting factor for crop production in many regions of the world and is considered one of the major limiting factors of rice production and food insecurity in Sudan. Conventional breeding for drought tolerance is further slowed down by the complex nature of mechanisms underlying this stress although molecular markers offer a promising alternative approach. Exposure of plants to drought stress has been shown to lead to a significant effect in chlorophyll content and eventual reduction in photosynthesis. In this study, 23 rice genotypes grown in Sudan were examined for drought tolerance under greenhouse conditions. The focus was on tracking changes in chlorophyll content under drought stress and further screening of the plants for DNA polymorphisms using simple sequence repeat (SSR) markers for possible associations. The results showed that genotypes IR11A306, IRRI 154, Nerica 6, IR12N240, Nerica 4, Wakra and IRRI 150 exhibited high drought tolerance based on this assay. After 7 days of dehydration, IR11A306 recorded the highest increment of total chlorophyll followed by IRRI 154, Nerica 6 and IR12N240, while IR11A483 showed the highest reduction followed by Nerica 15, IR11N121 and IRRI 168. When plants were rehydrated and total chlorophyll measured, the highest increase and best recovery were observed in IR74371-70-1-1 followed by IRRI 168, IRRI 147, Nipponbare and Kosti 2. Genotype IR11A306 showed the least reduction in chlorophyll levels followed by Nerica 15, IRRI 150 and IRRI 122. Eighteen primers showed amplification of the SSR markers generating 569 alleles that ranged between 13 to 113 alleles per marker. These alleles further produced polymorphism information content (PIC) values of 0.51 to 0.99 per marker. The chlorophyll assay helped select genotypes that showed a steady recovery of chlorophyll content following drought stress while the markers studied could be useful for future molecular breeding for drought tolerance in rice.