Assessment of Heat-tolerance Potential in QTL Introgressed Lines of Hybrid Rice Restorer, KMR-3R through PS-II Efficiency

Aims: To assess heat-induced PSII damage and efficiency in eight promising backcross introgression lines (BC2F6) of KMR-3R/N22 possessing qHTSF1.1 and qHTSF4.1.

Study Design: Randomized Complete Block Design (RCBD) with three replications.

Place and Duration of Study: ICAR-Indian Institute of Rice Research, Hyderabad India during wet/rainy (Kharif) season 2018.

Methodology: Eight ILs (BC2F6) and parents were evaluated for heat tolerance. The high- temperature stress was imposed by enclosing the crop with a poly cover tent (Polyhouse) just before the anthesis stage. The fluorescence parameters viz., maximum efficiency of PSII photochemistry (Fv/Fm), Electron transport rate (ETR), effective PSII quantum yield (ΦPSII), coefficient of photochemical quenching (qP) and coefficient of non-photochemical quenching (qN) were measured under ambient and high-temperature stress.

Results: The heat-tolerance potential of ILs was assessed in terms of PSII activity. The results indicated that significant differences were observed between treatments (T), genotypes (G) and the interaction between T × G. The physiological basis of introgressed QTLs controls the spikelet fertility by maintaining the productive and adaptive strategies in heat-tolerant QTL introgressed lines with stable photosynthetic apparatus (PSII) under high-temperature stress.

Conclusion: The Fv/Fm ratio denotes the maximum quantum yield of PSII. The heat-tolerant QTL introgressed lines exhibited stable photosynthetic apparatus (PSII) and noted better performance under high-temperature stress. They may be used as donors for fluorescence traits in breeding rice for high-temperature tolerance.