title: Elevated Ozone Deteriorates Grain Quality of Japonica Rice cv. Koshihikari, Even if it Does Not Cause Yield Reduction.
abstract: BACKGROUND
  It is becoming clear that ozone affects not only grain yield but also grain quality in rice. However, the biochemical mechanisms responsible for ozone-induced changes in appearance quality or components are poorly understood. We analyzed appearance quality and starch composition in the rice cultivars "Koshihikari" (japonica) and "Kasalath" (indica) grown under elevated ozone conditions.
  
  
  RESULTS
  Elevated ozone significantly increased the proportion of immature (mainly chalky) kernels in "Koshihikari" but not in "Kasalath". Scanning electron microscopy of transverse sections of kernels showed that endosperm starch granules of "Koshihikari" ripened under elevated ozone were loosely packed with large spaces and contained irregular rounded granules. Amylose content was increased in "Koshihikari" kernels with ozone exposure, but was unchanged in "Kasalath" kernels. Distribution analysis of amylopectin chain length showed that ozone induces a decrease of long-side chains and alterations of short side-chains in "Koshihikari" kernels. Furthermore, Starch Synthase (SS) IIIa transcript levels in "Koshihikari" caryopses were decreased by elevated ozone.
  
  
  CONCLUSIONS
  The japonica cultivar "Koshihikari" showed significant deterioration in appearance quality of kernels caused by abnormal starch accumulation due to exposure to ozone. The alteration patterns of amylose and amylopectin in ozone-exposed rice kernels are similar to those in rice kernels harvested from SSIIIa-deficient mutants. These findings suggest that the increase of chalky kernels in ozone-treated "Koshihikari" is partly attributable to the repressed expression of SSIIIa involved in amylopectin side-chain elongation with ozone exposure. Elevated ozone reduced appearance quality in "Koshihikari" although it did not impair starch properties contributing to the eating quality of cooked rice.
authors.affiliation: Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki, 305-8506, Japan.|JSPS Research Fellow, Japan Society for the Promotion of Science, ᅟChiyoda-ku, Tokyo, 102-0083, ᅟJapan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Sawada
authors.affiliation: Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki, 305-8506, Japan.
authors.forename: Keita
authors.initials: K
authors.lastname: Tsukahara
authors.affiliation: Central Research Institute of Electric Power Industry, Abiko, Chiba, 270-1194, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kohno
authors.affiliation: NARO Institute of Crop Science, Tsukuba, Ibaraki, 305-8518, Japan.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Department of Agribusiness, Akita Prefectural University, Minami akita-gun, Akita, 010-0444, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Nagasawa
authors.affiliation: Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki, 305-8506, Japan. mtamaoki@nies.go.jp.
authors.forename: Masanori
authors.initials: M
authors.lastname: Tamaoki
keywords: Grain Quality; Ozone Stress; Rice; Starch