Low-temperature Stress Influences Organic Osmolytes, Antioxidants and Physiological Traits at Reproductive Stage of Rice (Oryza sativa L.) Varieties in Late-Kharif Planting

Rice (Oryza sativa L.) is a staple food for most countries, originated from tropical areas and sensitive to low-temperature or temperate regions. A field experiment was conducted in at ARS, Ganagavathi, UAS, Raichur, Karnataka for two consecutive years (2020&2021). The experiment was laid out in two factorial randomized block design (RBD) in two dates of transplanting that is Kharif (K-15th September) and late-Kharif season (LK-30th September) with four varieties i.e., GNV-10-89 and GNV-1108 (short duration) and GNV-1801 and BPT-5204 (long duration) in three replications. The low-temperature at reproductive stage of late-Kharif season was 14±1oC., the results obtained at reproductive stage, proline content was higher in LK than K. Long duration varieties showed higher than short duration varieties. The total soluble sugar was higher in K and lower in LK, short duration varieties possessed higher than long duration varieties. The antioxidants activity like catalase (EC 1.11.1.6), peroxidase (EC 1.11.1.7), ascorbate peroxidase (EC 1.11.1.11) and super oxide dismutase (EC 1.15.1.1) was higher in the low-temperature stress condition that is LK than K and among varieties, long duration varieties showed higher antioxidants activity than short duration varieties. Photosynthetic rate and transpiration rate was higher in K and lower in LK, short duration varieties obtained higher than long duration varieties. Grain yield per hill was higher in K than LK and short duration varieties recorded higher than long duration varieties. This study concludes that the low-temperature encounter the reproductive stage of long duration varieties transplanted in LK.