Drought is one of the biggest challenges for rice (Oryza sativa L.) production in rainfed areas. Developing "aerobic rice" cultivars could be a valuable alternative to irrigated/rainfed areas. During 2010-2013, 115 rice genotypes, including non-local cultivars and aerobic rice genotypes, were evaluated and 31 rice genotypes were screened, while 21 Iranian lowland rice cultivars (52 genotypes) were investigated under non-stress and drought conditions at the University of Guilan, Rasht, Iran, in 2014 and 2017. The results revealed the superiority of high yielding genotypes, namely Neda (6.202 t ha- 1), IR82639-B-B-140-1 (6.020 t ha- 1), and IR82635-B-B-82-2 (5.75 t ha- 1) under non-stress, Panda (4.512 t ha- 1), and IR82639-B-B-140-1 (4.08 t ha- 1), under drought stress conditions. Based on the molecular markers evaluation using identified SSR markers linked to major QTLs different important traits specially drought stress, IR 82639-B-B-140-1 showed the highest genetic distance with high-quality Iranian lowland cultivars, which could be considered as a donor for the development of new cultivars. Moreover, the assignment of rice genotypes based on Jaccard distance clustering was in agreement with the grouping of structure analysis. The validation test using MLM analysis in this natural population revealed the most important significant associations that were identified under drought conditions. These are: the associations between RM306, RM319, RM511, RM28166, and RM11943 with different grain yield (GY)-related traits simultaneously and stable across both years. These markers, which were verified in a natural population across 2 years, could be considered as the potential markers for use in marker-assisted breeding and to improve the grain yield of rice.
Keywords: Aerobic rice; Genetic diversity; Lowland rice; Microsatellite markers; Water limited stress.