Submergence Tolerance in Rice (Oryza sativa L.) Genotypes at the Seedling Stage: A Combined Approach of Morphological and Molecular Characterization

Background: Rice (Oryza sativa L.) is the major cereal crop often suffers from submergence in the rainfed growing situation of India and South East Asia. Developing rice cultivars with tolerance to submergence is the best strategy to circumvent the situation. In Eastern India a vast reservoir of rice genotypes exists grown in diverse agro-climatic situation under rainfed condition. Screening rice genotypes under submergence stressed condition by observing morphological traits combined with molecular marker approach helps to identify the genotypes having innate capacity to survive under flooding condition more precisely than either of the approach alone. The present study was framed to identify the landraces and genotypes having the presence of desired genes which will helpful for future breeding program. Methods: Fifty rice (Oryza sativa L.) genotypes were evaluated for submergence tolerance using both morphological and molecular characterization in the field and laboratory respectively. Six stress indices, namely elongation%, survival%, mortality%, relative growth index, dry mass% and recovery rate, were examined in the field seven days and fourteen days after submergence. The genotypes were screened with SSR markers to identify the presence of the desired gene. Result: Based on morphological and molecular screening, out of all rice genotypes, Brahmabalak, Jaladhi 1-2, Jaldubi, Kerala Sundary, China IRRI, Sonachur, Pravat, Pankaj, Ranjit SUB1 and Bahadur SUB1 showed higher levels of tolerance to submergence than the tolerant control Swarna SUB1. They have one or more loci different from the SUB1 locus, which can be bred to create improved submergence-tolerant rice varieties with high yield in the rainfed lowland agroecosystem.