An Examination of a Rice-Breeding Method Using IR24 and the Thai Jasmine Rice Variety KDML105 for Early Heading Based on Combined Marker-Assisted and Phenotypic Selection

抄録

The Thai rice variety Khao Dawk Mali 105 (KDML105) is the most important of the rice strains grown in Thailand. However, this can be planted only once a year during the rainy season due to several cultivation constraints. The flowering time (or heading date) is one of the most important agronomic traits of crops. The plants’ response to the flowering time is considered an aspect of their adaptation to climate change, which affects their yield potential. We conducted this study to (i) improve Thai rice varieties by giving them the ability to escape dehydration and (ii) contribute to a database and future rice breeding programs in unpredicTable conditions. Regarding the heading trait expression of F₂-hybrid plants, we observed that under the long-day conditions, both rice hybrid cultivars had 50% days to heading (DTH): at 105–125 days after sowing (DAS) in KDML105/IR24 and 110–125 DAS in IR24/KDML105. A F₃-phenotyping analysis revealed that KDML105/IR24 on lines 27, 36, and 73 and IR24/KDML105 on lines 7, 70, and 77 had low variations of DTH. These six lines are considered homozygous strains with a fixed heading period. In the genotyping of F₃, we observed that KDML/IR24 on lines 27, 69, 73, and 87, including the combination of IR24/KDML105 line 7, had the same expressions of Hd1 and Hd3a as IR24 (the parent plant) and did not express DTH8. Based on these data, these five lines can be used for future breeding programs.