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Thailand's First High-Temperature-Tolerant Rice Variety, “Kimhan”
By Assoc. Prof. Dr. Chanate Malumpong Department of Agronomy, Faculty of Agriculture at Kamphaeng Saen, and team
- Dr. Surai Laman Jeh-abu — Faculty of Agriculture, Princess of Naradhiwas University
- Assoc. Prof. Dr. Siwaret Arikit — Department of Agronomy, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University
- Dr. Siriphat Ruengphayak — Rice Science Center, Kasetsart University
- Mr. Peerapon Muangngam — Pathum Thani Rice Research Center, Rice Department
- Ms. Bangorn Thammasamisorn — National Rice Science Institute, Rice Department
- Assoc. Prof. Dr. Apichart Vanavichit — Rice Science Center, Kasetsart University
- Mr. Suniyom Taprab — Rice Department, Ministry of Agriculture and Cooperatives
The project to find high-temperature-tolerant lines from the Hom Nin mutant rice population and to breed high-temperature-tolerant rice was funded by the Agricultural Research Development Agency for fiscal years 2011–2018 (B.E. 2554–2561). It began by searching the Hom Nin mutant population of 12,000 lines and found the line M9962, which tolerates a high temperature of 40°C at the reproductive stage.
Crossing began between Phitsanulok 2 (recipient: female parent) × line M9962 (heat-tolerant donor: male parent) in 2013 (B.E. 2556), giving the first-generation hybrid, which was backcrossed to Phitsanulok 2 two more times to give the BC2F1 generation. It was then self-pollinated and selected by pedigree selection up to the BC2F4 generation in a temperature-controlled greenhouse with daytime temperature (40–42°C), and then a preliminary yield trial was carried out.
4 selected lines of the BC2F5 generation were tested at Kasetsart University, Kamphaeng Saen Campus, in the 2018 (B.E. 2561) off-season, both in the field and in the temperature-controlled greenhouse. Finally, yield testing of BC2F7 lines was carried out in the 2019 (B.E. 2562) off-season at 4 locations:
- Kasetsart University, Kamphaeng Saen Campus
- National Rice Research Institute, Suphan Buri Province
- Pathum Thani Rice Research Center
- Temperature-controlled greenhouse
The results found that BC2F7-6-5-4-1-1-21 has a plant type close to Phitsanulok 2 but gives better yield and seed set under high temperature (>40°C), so this line was named
> Kimhan
meaning rice suited to growing in the summer season
It received a plant variety registration certificate under the Plant Variety Act B.E. 2518 (1975) on 5 July 2021 (B.E. 2564)
Image comparing the plant type of Kimhan with Phitsanulok 2 (female parent) and line M9962 (male parent)
Variety characteristics
- Non-glutinous rice, height about 95 centimeters
- Photoperiod insensitive, harvest age about 120 days
- Upright hill, dark green leaves, upright flag leaf, moderately dense panicle
- Straw-colored paddy
- Long, slender grains
- Paddy grain size 10.1 × 2.5 mm
- Milled rice grain size 7.6 × 2.0 mm
- Alkaline spreading test value level 7
- Amylose content 30% (hard-textured rice)
- Cooked rice quality: loose, firm
- Tolerates temperatures of 40–42°C with seed set of more than 70%
- Off-season yield 830 kilograms/rai
*Diagram of the breeding scheme for Kimhan (BC2F7-6-5-4-1-1-21)*
*Image of the off-season yield trial plot, Kasetsart University, Kamphaeng Saen Campus*
*Image of Kimhan panicles harvested from the off-season yield trial plot*
## Department of Agronomy, Faculty of Agriculture at Kamphaeng Saen https://agron.agri.kps.ku.ac.th
