Association between ABA- and drought-mediated regulation of root traits and identification of potential SNPs in genes for root development in rice

Abstract

Genetic improvement in root traits is necessary to enhance and stabilize yield of rice crop under rainfed ecosystem. Drought stress induces abscisic acid (ABA) accumulation, which in turn regulates root growth under drought. Hence, screening of genotypes based of ABA-responsiveness of root traits in simple hydroponics system can help to identify genotypes which may have better root traits under field drought stress conditions. Towards this objective, a set of 32 rice genotypes were phenotyped for root traits in 500 nM ABA at seedling stage in hydroponics, and then evaluated under drought stress (soil matric potential -70 kPa) at anthesis stage in field conditions. When the 32 genotypes were classified based on stress susceptibility index (SSI), 11 genotypes showed superior performance in both ABA stress and yield under drought stress in field, while 12 genotypes performed poor under both conditions. The SSI based classification of genotypes under ABA response as well as drought matched with yield for 7 good performing and 7 poor performing genotypes. Thus rice genotypes, CR2624, Ching Moiramsbhi, IC526266, Moroberekan, Nerica- L26, Nerica-L42 and Sahbhagi Dhan, which exhibited enhancement or stability in root length in response to ABA, also showed stability in both root length and yield under drought stress in field conditions. Single Nucleotide Polymorphism (SNP) analysis led to the identification of 20 non-synonymous SNPs in 12 genes involved in root traits. Clustering based on these SNPs could differentiate the genotypes with better root traits from that with poor root traits. This study shows that screening for ABAresponsiveness in root traits is a potential surrogate to identify donors for better root traits under drought stress in field conditions.