Effects Of Double-Stage Low Temperature At Jointing And Booting Stages On Grain Quality Of Wheat

With the development of economic and the improvement of people’s living standard,the quality of wheat grain is more and more concerned by people,and the contradiction between high yield and high quality of wheat is becoming more and more prominent.Therefore,the simultaneous improvement of yield and quality has become one of the main goals of wheat production.Wheat quality is a complex comprehensive trait that is controlled not only by the characteristics of the variety,but also by the environmental conditions.According to the previous studies,the effects of temperature on wheat grain quality is more prominent in the environmental factors.With global warming,the frequency and intensity of low temperature events in spring are also increasing,which have exacerbated the instability of wheat production systems and reduced the grain yield and quality of wheat.Therefore,study on the impact of multiple cold damage on the formation of wheat grain quality in spring can provide theoretical reference and data support for the improvement of wheat quality and the effective utilization of wheat grain in the future.In this study,two-year environment-controlled experiments under different low temperature levels at jointing stage,booting stage and both jointing and booting stages were conducted with two cultivars,the cold-sensitive cultivar Yangmail6 and the cold-tolerant cultivar Xumai30,were conducted.The objectives of this study were to（1）analyze and quantify the effects of low temperature on grain quality formation of wheat,and the spatial distribution of grain protein;（2）explore whether the early low temperature can improve the resistance of wheat then reduce the effect of low temperature on wheat grain quality in the later period.The main results of this study were as follows:（1）After low temperature treatment,the contents of total protein for two cultivars exhibited increasing trends with the decreasing low temperature levels,while the contents of the starch and its component and the accumulation of the total protein,starch and its component exhibited decreasing trends with the temperature decreasing,during grain filling.The effects of low temperature at booting stage on the contents and accumulation of the total protein and the accumulation of the starch and its component were greater than that at both jointing and booting stages and only jointing stage,except for amylopectin and total starch of Yangmail6.The effects of low temperature at both jointing and booting stages on the contents of the starch and its component were greater than that at only booting stage and jointing stage,except for amylose of Xumai30.Low temperature at the jointing stage has an effect of cold acclimation on the wheat,and the effect shows an increasing trend as the temperature decreases.The characteristic parameters of protein,starch and its component accumulation form logistic exhibited decreasing trends with temperature decreasing.Low temperature has the greatest effect on the maximum accumulation rate（Rmax）and the lowest effect on the accumulation active growth period（D）.In addition,the characteristic parameters of protein accumulation were highly correlated with the air temperature based accumulation cold degree days（ACDDa）,the characteristic parameters of starch and its component accumulation were highly correlated with the canopy temperature based accumulation cold degree days（ACDDc）.（2）Low temperature has a significant effect on the quality of mature wheat grain（except for the content of albumins and the ratio between grain length and width of Yangmai16）.Low temperature at booting stage has the greatest effect on wheat grain quality,followed by both jointing and booting stages,and the effect of low temperature at jointing stage was minimal.With temperature decreasing,the contents of total protein,globulin,gliadin,dry gluten,wet gluten and sedimentation value exhibited increasing trends,while the contents of total starch,amylose,amylopectin,grain length and grain width exhibited decreasing trends.Low temperature at the jointing stage has a certain cold acclimation on wheat,which could partly offset the negative effect of cold stress on wheat grain quality,and among the quality indexes,the cold acclimation effect was greatest of gliadin and lowest of Am/AP.In addition,there was a certain correlation between grain quality indexes and the accumulation cold degree days.For nutritional and appearance quality,the correlation was higher with ACDDc,while for the processing quality,highly correlated relationship was observed with ACDDa.（3）The contents of protein in wheat grains increased first and then decreased from outermost to innermost,and protein contents is highest in the aleurone layer（Yangmail6 at P2 and Xumai30 at P3）,and lowest in the inner endosperm layer（P9）.After low temperature treatment,the contents of protein in the same layers showed an increasing trend with temperature decreasing.Low temperature at both jointing and booting stages and booting stage has the greatest effect on the spatial distribution of grain protein of Yangmail6 and Xumai30 than only at jointing stage.Moreover,the effects of low temperature on the protein contents in different layers of Yangmai16 and Xumai30 were different.Low temperature at jointing stage and at both jointing and booting stages had the greatest effect on the protein contents of aleurone layer（P2 and P3）of Yangmai16 and seed husk（P1）and aleurone layer（P2 and P3）and outer endosperm（P5）of Xumai30.Low temperature at booting stage,had the greatest influence on the protein contents of outer endosperm（P5）and middle endosperm（P7）of Yangmail6 and middle endosperm（P6）of Xumai30.In addition,the protein contents of the inner endosperm（P9）of the two cultivars were less affected by low temperature.Low temperature at the jointing stage had cold acclimation on the spatial distribution of grain protein.The cold acclimation effect was greatest of protein contents in P1（Yangmail6）and P6 μ（Xumai30）layers,while was lowest in P9 layers of both Yangmail6 and Xumai30.Moreover,the relative concentrations of protein in aleurone layer（P2 and P3）,outer endosperm（P4）and middle endosperm（P7）were highly correlated with ACDDc,after low temperature treatment at jointing stage and both jointing and booting stages.However,after low temperature treatments at booting stage,the relative concentration of protein in each layer was highly correlated with ACDDc,except for husk（P1）and middle endosperm（P6）.