Oxidative metabolism, moisture imbibing capacity and their association with pre-harvest sprouting in rice

Rice grains are the major source of nutrition for more than half of the world's population. With increased frequencies of cyclones in the last decade during grain maturation stage of rice crop, most of the rice cultivars in lowland ecologies are getting affected by pre harvest sprouting due to flash flooding and incessant rains. Significant economic loss is incurred in the global food grain industry of cereals due to pre-harvest sprouting (PHS). It is very important to develop climate resilient varieties with PHS resistant traits introgressed in them. Well characterized PHS resistant rice genotypes with optimal dormancy that can serve as donors are need of the hour. We conducted an experiment to identify PHS resistant genotypes, and also determine to their physiological and biochemical characteristics. 96 diverse rice genotypes were evaluated for PHS resistance from 20 to 40 days after flowering (DAF). Based on their response, 16 contrasting genotypes were identified from 96 genotypes to further study the underlying mechanism of PHS resistance. The results revealed that, susceptible genotypes (8) exhibited very high germination percentage (4 to 87.5%), while resistant genotypes (8) exhibited zero germination at all the stages of study. Susceptible genotypes had higher levels of reactive oxygen species (H2O2 and O2−) and malondialdehyde (MDA) in their leaves (flag leaf) and seeds than resistant genotypes indicating a better stress protection mechanism in the resistant genotypes. The ability to imbibe moisture upon treatment also varied among the contrasting genotypes. In a nutshell, the present study revealed that better ROS scavenging mechanism, lower lipid peroxidation along with lesser moisture absorption capacity could have contributed to PHS resistance in the resistant genotypes.