Evaluation of different seed treatments to withstand submergence conditions of rice (Oryza sativa l.) at the early stage of growth.

Abstract

Rice (Oryza sativa L.) is a staple food widely cultivated as a lowland crop in Sri Lanka. Flooding significantly impacts direct-seeded rice planting in many rice growing areas of Sri Lanka. This study aimed to develop and evaluate various seed treatments to enhance crop performance and withstand submergence stress during the early developmental stage of the crop. The experiment followed a two factorial randomized complete block design (RCBD) with three replicates. Seed dormancy was eliminated by subjecting the seeds to 50°C for 5 days. Healthy seeds having more than 85% of germination percentage from three promising rice lines (BW-NP-14-7-5, N2B4, S2B7) and three rice varieties (Ld 368, Ld 253, Bw 372) were coated with Calcium Oxide (CaO) (20:6), Alginate (20:3), Sodium Lauryl Sulphate (SLS) (40:9) and primed with Calcium Chloride (CaCl2) (20:3) on a dry weight basis (g). Untreated seeds served as control. Germinated seeds were completely submerged under 1m water level for twelve days. Among all treatments seed treated with CaCl2 and Alginate resulted in a shorter mean emergence time, higher emergence index, and higher final emergence percentage. Significant interactions (p<0.005) between seed treatment and variety indicated that submergence tolerance depends on both factors of the factorial experiment. Survival percentage on the 14th day recovery period showed significant differences (p<0.005), with the highest survival percentage exhibited by Ld 253 under Alginate treatment. Rice varieties demonstrated varying responses to submergence stress, altering shoot and root growth dynamics. Although, plant height did not significantly differ among the seed treatments, shoot elongation rate post-desubmergence showed significant differences (p<0.005). Root lengths were higher in all seed treatments compared to non-treated seeds under submergence conditions. The observed phenomenon of reduced plant height and enhanced root length resulting from seed treatments under submergence conditions suggests that the plants had tried to tolerate submergence stress through the quiescence strategy. A better vigour index of the seedlings in all rice lines and varieties except N2B4 was observed by CaCl2 and Alginate under complete submergence. The results underscored the significance of CaCl2 and Alginate as promising seed treatment agents to enhance submergence tolerance in rice.