Yamada, Shuto, Kurokawa, Yusuke, Nagai, Keisuke, Angeles-Shim, Rosalyn B, Yasui, Hideshi, Furuya, Naruto, Yoshimura, Atsushi, Doi, Kazuyuki, Ashikari, Motoyuki, and Sunohara, Hidehiko
The yield-related gene, WFP increases grain number by increasing the primary branch number per panicle in rice. In the present study, WFP was introgressed from ST-12 to IRBB60, a pyramiding line having the genes Xa4, xa5, xa13 and Xa21 for BLB resistance in the IR24 genetic background. The pyramided lines PL-1, PL-4 and PL-5 that were included in the initial BC2F2 selections based on their improved PBN were selected for further agronomic evaluation and generation advance up to BC2F3. All three lines recorded significantly higher PBN and GN due WFP introgression, although the loss of at least two BLB genes during the breeding process resulted in the variable response of the lines to the different BLB races. Among the lines, only PL-5 showed a significantly higher estimate of actual yield measured in terms of panicle weight per square meter compared to IRBB60. PL-5 also exhibited resistance to five out of the six BLB races used for resistance screening. Despite the negative effects in grain size, the improved yield estimates, as well as the validated BLB resistance of PL-5 makes it a suitable candidate for cultivar adoption under the tropical rice ecosystem of Southeast Asia., イネ収量関連遺伝子WFPは、一次枝梗数増加による着粒数増加をもたらす。IR24に白葉枯病抵抗性遺伝子群（Xa4、xa5、xa13、Xa21）を集積したIRBB60へ、ST-12が持つWFPの導入を行った。IRBB60を反復親とした戻し交雑後代BC2F2とBC2F3世代で、DNAマーカーの利用と一次枝梗数を含む収量形質の評価から、3ピラミディング系統（PL-1、PL-4、PL-5）を選抜した。BC2F4において、これらはWFPによる一次枝梗数と着粒数の増加を示したが、4白葉枯病抵抗性遺伝子の集積が不完全で、白葉枯病レース群への反応の差が見られた。しかし、PL-5はIRBB60よりも収量増加が見込まれ、今回供試した白葉枯病レース（ベトナム、ミャンマー、インド由来6レース）の内5レースに対して抵抗性を示したことから、PL-5は東南アジアの熱帯地域での展開を見込んだ候補系統となり得ると考えられた。