A controlled seven-day heat treatment at 41/28°C during the milky stage showed cultivar-specific changes in phenology, dry-matter translocation, seed set and yield components. N22, Dular and SPT1 were classified as tolerant, while Thai cultivars spanned moderately tolerant to sensitive responses.
Key findings
- RD41 increased selected dry-matter measures under heat, PSL2 showed strong assimilate translocation, CN1 and RD49 lost substantial yield, RD63 declined across yield components, and N22 maintained performance. Phenological shift and seed set emerged as useful joint indicators. N22, Dular and SPT1 were tolerant, while IR64, PTT1, RD29, RD31, RD49, RD57 and RD63 were sensitive.
Why this matters globally
As heat waves increasingly strike rice reproductive stages, cultivar-specific mechanisms can help breeding programmes select both germplasm and measurable traits rather than rely only on final yield.
Thai researcher contribution
The Khon Kaen and Roi Et Rajabhat team compared multiple Thai cultivars with international references, identifying candidate tolerance sources and vulnerable cultivars under warming conditions.
Limitations to consider
This was a short controlled experiment without multi-location or multi-season validation, and heat was separated from drought, humidity and realistic night-temperature variation. The relationship between the reported cultivar set and the final classification should be checked in the full design, and molecular mechanisms were not validated.