title: Confirming a major QTL and finding additional loci responsible for field resistance to brown spot (Bipolaris oryzae) in rice.
abstract: Brown spot is a devastating rice disease. Quantitative resistance has been observed in local varieties (e.g., 'Tadukan'), but no economically useful resistant variety has been bred. Using quantitative trait locus (QTL) analysis of recombinant inbred lines (RILs) from 'Tadukan' (resistant) × 'Hinohikari' (susceptible), we previously found three QTLs (qBS2, qBS9, and qBS11) that conferred resistance in seedlings in a greenhouse. To confirm their effect, the parents and later generations of RILs were transplanted into paddy fields where brown spot severely occurred. Three new resistance QTLs (qBSfR1, qBSfR4, and qBSfR11) were detected on chromosomes 1, 4, and 11, respectively. The 'Tadukan' alleles at qBSfR1 and qBSfR11 and the 'Hinohikari' allele at qBSfR4 increased resistance. The major QTL qBSfR11 coincided with qBS11 from the previous study, whereas qBSfR1 and qBSfR4 were new but neither qBS2 nor qBS9 were detected. To verify the qBSfR1 and qBSfR11 'Tadukan' resistance alleles, near-isogenic lines (NILs) with one or both QTLs in a susceptible background ('Koshihikari') were evaluated under field conditions. NILs with qBSfR11 acquired significant field resistance; those with qBSfR1 did not. This confirms the effectiveness of qBSfR11. Genetic markers flanking qBSfR11 will be powerful tools for marker-assisted selection to improve brown spot resistance.
authors.affiliation: National Agriculture and Food Research Organization, Kyushu Okinawa Agriculture Research Center (NARO/KARC) , 496 Izumi Chikugo, Fukuoka 833-0041 , Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sato
authors.affiliation: Mie Prefecture Agricultural Research Institute , 530 Kawakita, Ureshino, Mie 515-2316 , Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Matsumoto
authors.affiliation: Mie Prefecture Agricultural Research Institute , 530 Kawakita, Ureshino, Mie 515-2316 , Japan.
authors.forename: Chihiro
authors.initials: C
authors.lastname: Ota
authors.affiliation: Mie Prefecture Agricultural Research Institute , 530 Kawakita, Ureshino, Mie 515-2316 , Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Yamakawa
authors.affiliation: Faculty of Life and Environmental Science, Shimane University , 1060 Nishikawatsu, Matsue, Shimane 690-8504 , Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Kihara
authors.affiliation: National Institute of Agrobiological Sciences (NIAS) , 2-1-2, Kannondai, Tsukuba, Ibaraki 305-8602 , Japan.
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Mizobuchi
keywords: Bipolaris oryzae; Oryza sativa L.; QTL analysis; brown spot; field resistance; rice