title: Shading during the grain filling period increases 2-acetyl-1-pyrroline content in fragrant rice.
abstract: BACKGROUND
  Fragrant rice, including Thai jasmine and Indian basmati varieties, is highly valued by consumers globally. 2-acetyl-1-proline (2-AP) is the major compound responsible for the aromatic character of fragrant rice. Previously, environmental factors such as water management and salinity have been proven to influence 2-AP levels in fragrant rice; assessing the effect of additional environmental factors on 2-AP concentration is therefore eminent. The level of solar radiation (solar intensity; SI) to which a crop is exposed can affect growth, yield and grain quality, and other photosynthetic and physiological characteristics. In this study the effect of shading (i.e. the reduction of SI) on yield, quality, and 2-AP concentration in two elite Chinese fragrant rice varieties, 'Yuxiangyouzhan' and 'Nongxiang 18', has been investigated. Furthermore, accumulation of the plant stress response molecules proline and gamma-aminobutyric acid, which have also been implicated in pathways leading to 2-AP production, was assessed to study shading effects on these compounds in fragrant rice, and to further possibly determine fluxes in biochemical pathways leading to 2-AP accumulation.
  
  
  RESULTS
  This study has revealed significant changes in the yield and quality characters under shading treatment. Additionally, 2-AP and GABA content in grains was significantly increased for all shading treatments in both varieties. In addition to 2-AP, ten other volatile compounds were studied; results indicated that shading treatments could have a selective effect on the metabolism of these volatile compounds.
  
  
  CONCLUSIONS
  In this study, we have demonstrated that shading during grain filling has significant effects on yield and quality traits in rice, and leads to the accumulation of GABA and 2-AP. We discuss the implications of these findings in terms of pathways leading to 2-AP and GABA production in fragrant rice, which have not been fully elucidated. The shading effect on ten additional volatile compounds is also discussed. Finally we discuss possible effects of variation in solar intensity resulting from anthropogenic emissions on fragrant rice production.
authors.affiliation: College of Agriculture, South China Agricultural University, Guangzhou, Guangdong, 510642 China ; Scientific Observing and Experimental Station of Crop Cultivation in South China, Ministry of Agriculture. P. R. China, Guangzhou, Guangdong 510642 China.
authors.forename: Zhaowen
authors.initials: Z
authors.lastname: Mo
authors.affiliation: Crops Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, Guangdong 510640 China.
authors.forename: Wu
authors.initials: W
authors.lastname: Li
authors.affiliation: College of Agriculture, South China Agricultural University, Guangzhou, Guangdong, 510642 China ; Scientific Observing and Experimental Station of Crop Cultivation in South China, Ministry of Agriculture. P. R. China, Guangzhou, Guangdong 510642 China.
authors.forename: Shenggang
authors.initials: S
authors.lastname: Pan
authors.affiliation: CSIRO Agriculture Flagship, Queensland Bioscience Precinct, 306 Carmody Rd, St Lucia, Queensland 4067 Australia.
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Fitzgerald
authors.affiliation: College of Agriculture, South China Agricultural University, Guangzhou, Guangdong, 510642 China.
authors.forename: Feng
authors.initials: F
authors.lastname: Xiao
authors.affiliation: College of Agriculture, South China Agricultural University, Guangzhou, Guangdong, 510642 China.
authors.forename: Yongjian
authors.initials: Y
authors.lastname: Tang
authors.affiliation: College of Agriculture, South China Agricultural University, Guangzhou, Guangdong, 510642 China.
authors.forename: Yilei
authors.initials: Y
authors.lastname: Wang
authors.affiliation: College of Agriculture, South China Agricultural University, Guangzhou, Guangdong, 510642 China ; Scientific Observing and Experimental Station of Crop Cultivation in South China, Ministry of Agriculture. P. R. China, Guangzhou, Guangdong 510642 China.
authors.forename: Meiyang
authors.initials: M
authors.lastname: Duan
authors.affiliation: College of Agriculture, South China Agricultural University, Guangzhou, Guangdong, 510642 China ; Scientific Observing and Experimental Station of Crop Cultivation in South China, Ministry of Agriculture. P. R. China, Guangzhou, Guangdong 510642 China.
authors.forename: Hua
authors.initials: H
authors.lastname: Tian
authors.affiliation: College of Agriculture, South China Agricultural University, Guangzhou, Guangdong, 510642 China ; Scientific Observing and Experimental Station of Crop Cultivation in South China, Ministry of Agriculture. P. R. China, Guangzhou, Guangdong 510642 China.
authors.forename: Xiangru
authors.initials: X
authors.lastname: Tang
keywords: 2-acetyl-1-pyrroline; Aromatic rice; Proline; Shading treatment; Yield; γ-aminobutyric acid
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