The Response To High Temperature During Grain Filling On Physicochemical Properties Of Waxy Maize Starch

The experiments were carried out in experimental farm of the Agricultural College of Yangzhou University in2011-2012, the effects for high temperature during grain filling stages on physicochemical properties of waxy maize grain starch were studied. The main results were as follows:1. The genotypic differences for the response to high temperature during grain filling on physicochemical properties of waxy maize grain starchPhysicochemical properties of waxy maize grain starch affect by high temperature during grain filling were significantly different among43waxy maize varieties or lines. Higher temperature decreased starch peak viscosity, trough viscosity, breakdown, enthalpy of retrogradation, and percentage of retrogradation, while it increased transition temperature (To, Tp and Tc), λmax, and percentage of large starch granule size. The results of correlation analysis observed that the iodine binding capacity and percentage of starch granule size that diameter between0-9μm was significantly negative correlated to breakdown and setback, and was significantly positive correlated to enthalpy of gelatinization, pasting temperature, and transition temperature. Starch granule size that diameter between13-17μm was significantly negative correlated to pasting temperature, and was significantly positive correlated to setback. The variety of peak viscosity increased the biggest under high temperature stress was Lainongnuo11, and that reduced the biggest was Huaikenuo3.2. Effects for high temperature during different grain filling stages on physicochemical properties of waxy maize flourHeat stress during different grain filling stages decreased the grain yield, starch content, peak viscosity of the four varieties of spring waxy maize (Suyunuo5, Yunuo7, Lainongnuo11, Huaikenuo3), and increased protein content, pasting temperature, transition temperature, percentage of retrogradation, starch average granule diameter and percentage of dents and irregular shape granules. These effects were more severe when heat stress at early development stage. Heat stress at early development stage reduced peak intensity and crystalline of the grain starch from four varieties, while heat stress at later development stage decreased peak intensity and crystalline of Suyunuo5and Yunuo7, and it increased peak intensity and crystalline of Huaikenuo3and Lainongnuo11. The results of correlation analysis observed that higher protein content, starch content reduced under heat stress was the main reason for the starch gelatinization, retrogradation and pasting characteristics become worse, starch average granule diameter, crystalline and iodine binding capacity also have certain effect with starch gelatinization, retrogradation and pasting characteristics.3. Effects for high temperature during different grain filling stages on physicochemical properties of waxy maize starchHeat stress during grain filling decreased waxy grain yield, total grain filling stage heat stress affected the most, followed by1-10DAP heat stress. Peak viscosity, trough viscosity and final viscosity of Yunuo7and Lainongnuo11were decreased by heat stress during grain filling, and it was lower at11-20DAP heat stress. Heat stress during each grain filling stages increased enthalpy of retrogradation for Suyunuo5and Yunuo7, and the increment was highest for heat stress at whole grain filling stage and late stage. Heat stress during each grain filling stages increased iodine binding capacity for four varieties, and each grain filling stages response to heat stress was variety-dependent. The percentage of large starch granule that diameter higher than13μm affected by heat stress during each grain filling stages was different with control, overall, the increment was more severe for heat stress during total grain filling stage, and decrement was more severe for11-20DAP stage. There was significant difference between physicochemical properties in different varieties.4. Effects for high temperature during different grain filling stages on physicochemical properties of fresh waxy maizeHigh temperature during grain filling decreased the grain numbers per ear and grain yield and the decrement was more severe for heat stress during total grain filling stage, followed by heat stress at early stage. Heat stress increased the grain starch content, and the increment was highest for heat stress at late stage. Heat stress during grain filling increased the starch average granule size and the percentage of large starch granule that diameter higher than13μm, and the increment was highest for heat stress at whole grain filling stage, followed by heat stress at early stage. Iodine binding capacity was increased under heat stress during whole grain filling or at11-20DAP, while it was decreased by heat stress at early kernel development. In general, heat stress increased the peak viscosity, breakdown and pasting temperature, and the increment was lowest for heat stress at early stage. Heat stress decreased the gelatinization enthalpy, and transition temperature was similar between control and heat stress during early stage, while it was increased by heat stress during late stage. Heat stress during early or late grain filling stage increased the retrogradation percentage, and the increment were more severe under heat stress at early stage, heat stress during whole grain filling stage increased the retrogradation percentage for Yunuo7, while it was decreased for Suyunuo5.5. Effects for different planting dates on physicochemical properties of waxy maizeGrain yield and physical and physicochemical properties of waxy maize was affected by different planting dates. Under the spring sowing treatment, the grain yield for Suyunuo5and Yunuo7planted at March15and23is higher, peak viscosity, trough viscosity, breakdown, final viscosity, and average grain diameter was higher at March15and23planting, and it was lower at April7. Under the summer sowing treatment, the grain yield for two varieties was higher planted at July1and16planting, starch content was highest for Suyunuo5at July1planting, and for Yunuo7at July16planting, and the both were lowest at July29planting. Peak viscosity, trough viscosity, breakdown, and final viscosity were higher for Suyunuo5planted at July1and16, and lowest at June15planting. Trough viscosity and final viscosity for Yunuo7were highest at July16planting, and lowest at July29planting. Peak viscosity for Yunuo7was lowest planted at July29, and no significant differences at other planting dates. Overall, in Yangzhou, spring maize should be planted in early time when the required minimum temperature was meet, to avoid or reduce the effects of the plant hopper and hot and mould rains during filling stage, summer maize planting should be postponed, which can avoid plant hopper impact and rainy weather and avert late grain filling stage affected by the low temperature.