Grain size is one of the most important factors determining grain yield in rice breeding. In previous studies, we constructed high-density maps for two quantitative trait loci (QTL) for grain weight, tgw2 and gw9.1, using progeny derived from crosses between the japonica cultivar Hwaseong and Oryza grandiglumis, and Hwaseong and O. rufipogon (IRGC 105491), respectively. The wild alleles contributed an increase in grain weight at these two loci. We developed an F₂ population (146 plants) by crossing two near isogenic lines (NILs) harboring tgw2 and gw9.1 to know how they interact in the near isogenic background. Simple sequence repeat markers tightly linked to two QTL were used to check the genotype of the F₂ population. Based on the genotype at two loci, 146 F₂ plants were classified into 9 groups with a combination of three genotypes at each two loci. Two gene interaction was not significant (P=0.99) in the F₂. Homozygous plants with wild alleles at two loci showed significantly higher 1,000 grain weight than plants with a single QTL in the F₂ and F₃. These results indicate that two QTLs act additively in distinct or complementary pathways in controlling GW. Gene expression analysis was also performed to know the relationship of the gw9.1 QTL with three major grain size genes with Hwaseong and two NILs plants at the transcription level. The results from this study provide insight into grain size regulation in rice and are likely to be useful for marker aided selection for grain size.

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• QTL Analysis Related to Grain Size Using the Population Derived from a Cross Between Hopum and Basmati 370
  Da-Eun Im, Seong-Gyu Jang, Backki Kim, Jeonghwan Seo, D. S. Kishor, Hee-Jong Koh, Soon-Wook Kwon
  Korean Journal of Breeding Science.2023; 55(2): 118.     CrossRef
• QTL-by-QTL, QTL-by-environment, and QTL-by-QTL-by-environment interactions of loci controlling grain length in rice
  Tsuneo Kato, Akira Horibata
  Euphytica.2022;[Epub]     CrossRef

Grain weight (GW) is one of the most important targets for grain yield in rice breeding. In previous studies, two quantitative trait loci (QTLs) for grain weight, tgw2 and gw8.1, were identified using progeny derived from crosses between the japonica cultivar Hwaseong and Oryza grandiglumis, and between Hwaseong and O. rufipogon (IRGC 105491), respectively. The wild alleles increased GW at two loci. An F₂ population (186 plants) was developed by crossing two near isogenic lines (NILs) harboring tgw2 and gw8.1 to test their interaction. Simple sequence repeat (SSR) markers tightly linked to the two QTLs were used to check the genotype of the F₂ population. Based on the genotype at the two loci, tgw2 and gw8.1, the F₂ plants were classified into 9 groups with a combination of three genotypes at each of the two loci. Two-way ANOVA revealed no interaction between the 2 QTLs in the F₂ population. The 1,000 grain weight (TGW) of homozygous plants with wild alleles at the two loci was significantly higher than that of plants with a single QTL in the F₂ and F₃ lines. These results indicate that two QTLs act additively, in distinct or complementary pathways, to control grain weight. Based on these results, it is desirable to pyramid the two QTLs into a single line, since the double-QTL line displayed further increase of TGW in the Hwaseong background.

Citations

Citations to this article as recorded by  

• QTL Analysis Related to Grain Size Using the Population Derived from a Cross Between Hopum and Basmati 370
  Da-Eun Im, Seong-Gyu Jang, Backki Kim, Jeonghwan Seo, D. S. Kishor, Hee-Jong Koh, Soon-Wook Kwon
  Korean Journal of Breeding Science.2023; 55(2): 118.     CrossRef
• QTL-by-QTL, QTL-by-environment, and QTL-by-QTL-by-environment interactions of loci controlling grain length in rice
  Tsuneo Kato, Akira Horibata
  Euphytica.2022;[Epub]     CrossRef
• Fine mapping and candidate gene analysis of the quantitative trait locus gw8.1 associated with grain length in rice
  Yun-Joo Kang, Kyu-Chan Shim, Hyun-Sook Lee, Yun-A Jeon, Sun-Ha Kim, Ju-Won Kang, Yeo-Tae Yun, In-Kyu Park, Sang-Nag Ahn
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  Euphytica.2017;[Epub]     CrossRef
• Path analysis and estimation of additive and epistatic gene effects of barley SSD lines
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