title: Distribution of photoperiod-insensitive alleles Ppd-B1a and Ppd-D1a and their effect on heading time in Japanese wheat cultivars.
abstract: The genotypes of photoperiod response genes Ppd-B1 and Ppd-D1 in Japanese wheat cultivars were determined by a PCR-based method, and heading times were compared among genotypes. Most of the Japanese wheat cultivars, except those from the Hokkaido region, carried the photoperiod-insensitive allele Ppd-D1a, and heading was accelerated 10.3 days compared with the Ppd-D1b genotype. Early cultivars with Ppd-D1a may have been selected to avoid damage from preharvest rain. In the Hokkaido region, Ppd-D1a frequency was lower and heading date was late regardless of Ppd-D1 genotype, suggesting another genetic mechanism for late heading in Hokkaido cultivars. In this study, only 11 cultivars proved to carry Ppd-B1a, and all of them carried another photoperiod-insensitive allele, Ppd-D1a. The Ppd-B1a/Ppd-D1a genotype headed 6.7 days earlier than the Ppd-B1b/Ppd-D1a genotype, indicating a significant effect of Ppd-B1a in the genetic background with Ppd-D1a. Early-maturity breeding in Japan is believed to be accelerated by the introduction of the Ppd-B1a allele into medium-heading cultivars carrying Ppd-D1a. Pedigree analysis showed that Ppd-B1a in three extra-early commercial cultivars was inherited from 'Shiroboro 21' by early-heading Chugoku lines bred at the Chugoku Agriculture Experimental Station.
authors.affiliation: NARO Institute of Crop Science , 2-1-18 Kannondai, Tsukuba, Ibaraki 305-8518, Japan ; Okayama Universitiy , 3-1-1 Tsushima-naka, Kita, Okayama 700-8530, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Seki
authors.forename: Makiko
authors.initials: M
authors.lastname: Chono
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Matsunaka
authors.forename: Masaya
authors.initials: M
authors.lastname: Fujita
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Oda
authors.forename: Katashi
authors.initials: K
authors.lastname: Kubo
authors.forename: Chikako
authors.initials: C
authors.lastname: Kiribuchi-Otobe
authors.forename: Hisayo
authors.initials: H
authors.lastname: Kojima
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Nishida
authors.forename: Kenji
authors.initials: K
authors.lastname: Kato
keywords: Japanese wheat cultivars; Ppd-B1; Ppd-D1; heading date; photoperiod response gene; wheat