Genotypic Differences For Grain Physicochemical Properties Of Fresh Waxy Maize And Its Response To Environmental Adversity During Grain Filling

The experiments were carried out in experimental farm of Yangzhou University in2010-2011, the genotypic differences for grain physicochemical characteristics of fresh waxy maize were studied, and its response to environmental adversity (higher temperature, water stress and shading) during grain filling were researched.The main results were as follows:1Genotypic differences for grain physicochemical characteristics of fresh waxy maizeSignificant differences for grain nutritional content and physicochemical characteristics were observed among five varieties. Starch content ranged from48.7%to72.2%, the lowest for Jingcaitiannuo and the highest for Shengnuo1. Protein content was observed between7.4%(Xuenuo8) and8.9%(Jingcaitiannuo). Iodine binding capacity (IBC) and the λmax ranged from0.433to0.919and from531.6nm to559.4nm, the lowest for Zhengbainuo968and the highest for Shennuo062. The variation range of blue value (BV) is between0.051(Zhengbainuo968) and0.152(Sida29). Elements content in grain was different among tested samples. K and P content was higher than other elements in the grain, and it was between3500.4and4337.3mg kg-1,2203.6and3084.0mg kg-1, respectively. RVA and DSC characteristics were observed different among various varieties. The results of correlation analysis observed that the onset temperature, peak temperature and final temperature was significantly positive correlated each other. Peak height index was significantly positive correlated to gelatinization enthalpy, while it was significantly negative correlated to gelatinization range. Gelatinization range was observed significantly negative correlated to gelatinization enthalpy, onset temperature and final temperature. Significantly postive correlations was observed between gelatinization enthalpy and retrogradation percentage.2. Effects of higher temperature during grain filling on grain quality characteristics Heat stress during grain filling decreased starch content of fresh waxy maize, increased the crude protein and protein fractions (albumin, globulin, gliadin and glutenin)content, while soluble sugar content were unchanged in general. Higher temperature decreased starch peak viscosity, trough viscosity, final viscosity, breakdown, and setback, while it increased the pasting temperature. Under heat stress treatment, the sample presented lower gelatinization enthalpy and higher transition temperature. The starch granules size distribution of various varieties response to heat stress was different. Iodine binding capacity were not affected by heat stress.3. Effects of water stress during grain filling on grain quality characteristicsFresh waxy maize crude protein and protein fractions (albumin, globulin, gliadin and glutenin) presented a fall first and increase later tendency with the increment of soil moisture Starch content was the lowest when the soil moisture was highest for Yunuo7, while it similar under different treaments for Suyunuo5. Soluble sugar, starch iodine binding capacity and pasting temperature were not affected by water stress. The peak viscosity, trough viscosity and breakdown for both varieties was increased first and fall later with the increment of soil moisture. Water stress has no significant effect on gelatinization enthalpy of the fresh waxy maize, while peak temperature of the two species was highest when are soil moisture was highest. Textural properties of fresh waxy maize was little affected by soil moisture.4. Effects of shading during grain filling on grain quality characteristicsShading during grain filling decreased the crude protein content, increased gliadin content, while gluten content was not affected. Soluble sugar content of the two species are significantly reduced by shading, while starch content was not affected. Pasting temperature and blue value was not affected by shading, while peak viscosity, trough viscosity, breakdown, final viscosity, and setback values were significantly decreased; Starch λmax and the iodine binding capacity was significantly decreased under the shading treatment. Shading stress decreased the retrogradation enthalpy and retrogradation percentage.