In Vitro Development and Heat Stress Tolerance in Rice (Oryza Sativa L.)

Abstract

Rice is a staple crop that provides food for billions of people worldwide, but it is susceptible to damage from biotic and abiotic stress, particularly in tropical or subtropical areas. On top of that, stress has a negative impact on the productivity and quality of rice. To close the gap between output and demand, significant productivity gains are needed given the rising demand for rice. The study assessed the germination rates and callus induction capabilities of various rice varieties under different conditions in lab and also in the field. An efficient and reproducible in vitro regeneration process is required for the production of abiotic stress tolerance in rice through biotechnological approaches. In this study, optimization of culture media, callus induction, and plant regeneration of five Aman rice varieties viz. BRRI dhan34, BRRI dhan51, BRRI dhan71, BRRI dhan79, and BRRI dhan95 were considered and mature seeds of those varieties were collected from BRRI Regional Station, Rajshahi. To investigate the effects of different concentrations of 2,4-D and other plant growth regulators on callus induction and regeneration some experiments were conducted and evaluated. Two basal media viz. MS and N6 were considered for the experiments out of four (MS, B5, N6 and SK-3) studied previously under this research works. It was observed that all five rice varieties showed higher callus induction on MS medium supplemented with 3.0 mg/l 2,4-D than other concentrations. Based on callus induction data were recorded and BRRI dhan34, BRRI dhan51, BRRI dhan71, BRRI dhan79 and BRRI dhan95 gave 63.4%, 50.4%, 40.4%, 58% and 53% embryogenic calli, induction respectively. In combination with BAP (2.0 mg/l), Kin (2.0 mg/l) and NAA (0.5 mg/l) added to MS medium data showed better performance on regeneration. They can be used as a baseline for demand-driven in vitro rice propagation, providing useful information that can be combined with other agronomic features in rice development to improve the abiotic stress-tolerant cultivars through biotechnological methods in future. In addition of different concentration of NaCl in medium affects on callus growth. Data showed that at 2.0 g/l concentration was better than others. Higher NaCl concentrations correlated with decreased germination rates and increased callus necrosis, although BRRI dhan34 (7.2±0.8%) and BRRI dhan51 (7.2±0.8%) exhibited salt tolerances across all studies concentrations. Another experiment was conducted on the effect of heat stress and results showed that BRRI dhan34, BRRI dhan79 and BRRI dhan95 showed tolerances and it was observed that maintaining robust callus growth even at elevated temperatures at 35°C and 40°C. In contrast, BRRI dhan51 (6%) and BRRI dhan71 (8%), displayed modest heat tolerance (6%), exhibiting diminished performance under higher temperatures. These findings are very importance on selecting appropriate rice varieties based on their germination rates, callus induction, salt and heat tolerance of rice varieties in Bangladesh.