Quantifying The Response Of The Grain Quality Of Wheat To DIM Light At Filling Stage

Light intensity is one of the most important environmental factors which affect the growth and yield of crops. Along with the global climate changing, cloudy and rainy climate become unfavorable events occurred frequently during filling stage of wheat at the Yangtze River Region, which is the main region of weak gluten wheat in China. The dim light events induced by cloudy and rainy climate cause direct effect on the yield and grain quality of wheat. Quantifying the influence of dim light on crop growth is the basis of assessing the impact of cloudy and rainy climate on crop yield and quality. The aim of this study is to quantitatively investigate the effect of low light on the wheat quality. Experiments of weak gluten wheat (Yangmai 15, Ningmai 9 and Yangmai 13) with different shading levels (50%,66%,84%) and duration (2d,4d,6d,8d) of shading treatment were conducted on the farm of Jiangsu Provincial Academy of Agricultural Sciences in Nanjing from November 2008 to June 2010. Through the data analysis, we determine the critical level of the combination of the shading level and its duration, exceeding which could significantly affect the wheat growth at the filling stage. The photo-thermal index intercepted by canopy after anthesis was used as a driving variable to describe the quantitative relationship between the quality of the weak gluten wheat and the low light conditions at wheat filling stage. Independent experimental data were used to validate the quantitative relationship. The main research results are as follows:(1) The effect of dim light on the grain quality of wheat. The dim light at filling stage caused the decrease of the total starch content, amylopectin content, the peak viscosity, through viscosity and final viscosity, while increased the crude protein, the wet gluten content, the SDS-sedimentation value and the falling number. Among the farinograph parameters, the softening degree of yangmai 15 decreased under the shading conditions. The wheat quality of the treatments changed significantly compared with the control when the shading and its duration exceeded 50% and 4d, or 84% and 2d. The more serious the shading and its duration occurred, the more significant difference displayed between the treatment and the control.(2) The determination of the quantitative relationship of the effects of dim light on the grain quality of wheat. Through the data analysis of yangmai15, the quantitative relationship among the grain weight, the grain nitrogen content per unit area and the photo-thermal index (PTI) intercepted by the canopy was defined. Then quantified the relationships among the quality indices, the grain weight and the grain nitrogen content per unit area and. Based on the quantitative relationships defined prior, predicted the effects of dim light on the quality of the weak gluten wheat. Independent experimental data were used to validate the quantitative relationships. The results showed that the coefficient of determination (r2) of grain weight, grain nitrogen accumulation between the predicted and measured results were 0.83,0.81, respectively. And the relative root mean square error (rRMSE) of grain weight, grain nitrogen accumulation between the predicted and measured results were 0.30,0.33. The coefficient of determination (r2) of bulk density, falling number, peak viscosity between the predicted and measured results were, respectively,0.65,0.63, 0.66. And the relative root mean square error (rRMSE) of bulk density, falling number, peak viscosity between the predicted and measured results were, respectively,0.16,0.13, 0.14. The coefficient of determination (r2) of crude protein, wet gluten content and the SDS-sedimentation value between the predicted and measured results were, respectively, 0.63,0.65,0.68. And the relative root mean square error (rRMSE) of crude protein, wet gluten content and the SDS-sedimentation value between the predicted and measured results were, respectively,0.09,0.10,0.08.A comprehensive photo-thermal index was considered in the quantitative relationships to describe the grain weight and the grain nitrogen content per unit area after anthesis. Based on the relationship of the grain weight, the nitrogen content per unit area and the grain quality, we predicted the quality of the weak gluten wheat under the low light event. The quantitative relationships included some parameters which have explicit biological significance, thus, the study can be used to supply an academic foundation for assessing the impact of wheat quality quantitatively under the low light event.