Effects Of Soil Moisture Stress During Grain Filling On Grain Yield And Starch Quality Of Waxy Maize

The experiments were carried out at the experimental farm in Agricultural College of Yangzhou University in2012-2013. The effects of soil moisture stress during grain filling on waxy maize grain yield and starch quality were studied using pot, pool and field trials. In addition, the differences in pasting and thermal properties between waxy maize flours and starches were clarified. The results indicated that the soil moisture stress decreased the grain numbers and weight of waxy maize, resulting in the lose of grain yield. Soil moisture stress decreased the grain starch content in general, while the protein and soluble sugar content response to water stress were dependent on varieties. In pool trials, the peak viscosity and breakdown of waxy maize flours were decreased and pasting temperature was increased. The effects of soil moisture stress on pasting temperature and breakdown of waxy maize starch were similar to its flours, while waxy maize starch peak viscosity were only decreased by waterlogging treatments. In pot trials, the pasting temperature for flour and starch of waxy maize was not influenced by soil moisture stress; the peak viscosity and breakdown of waxy maize flour response to water stress were similar to pool trials. Those two parameters in starches were both decreased by water deficit and waterlogging treatments. In pool trials, water stress increased the onset temperature, peak temperature, conclusion temperature and retrogradation percentage in flours, while the gelatinization enthalpy was only decreased in drought treatment. The starch gelatinization enthalpy were decreased by soil moisture stress, the onset temperature, peak temperature, and conclusion temperature were similar among different treatments, while retrogradation percentage was only increased by waterlogging treatments. In pot trials, the flour gelatinization enthalpy and retrogradation percentage were increased by water stress, the onset-, peak and conclusion temperature were gradually decreased with the increment of soil moisture content. Water stress decreased the gelatinization enthalpy and increased the retrogradation percentage, the peak temperature was only decreased by waterlogging treatment in general. The different response of pasting and thermal properties in waxy maize flours or starches to water stress afford references for selecting varieties. Water stress did not change the morphological property of starch granules, but the average starch granule size was decreased by drought or waterlogging treatments. The λmax, iodine binding capacity and setback of all waxy maize starch samples present waxy characters. Water stress did not change the crystalline type and all sample present typical "A" type diffraction pattern. Water deficit or oversupply treatment decreased the crystallinity in Yunuo7but it was only decreased under water deficit treatments in Suyunuo5. The swell power for flour in both varieties was higher under water oversupply treatments and it was similar between water deficit and water normal supply treatment. The starch swell power was increased by water deficit treatments in both varieties. The results of correlation analysis indicated that the starch average granule size was positive correlated to pasting temperature of waxy maize flour, while it was negatively correlated to peak temperature and retrogradation percentage of flour and starch. Iodine binding capacity was observed negatively correlated to breakdown viscosity of flour, peak viscosity and breakdown of starch, and it positively correlated to pasting temperature of waxy maize flour, gelatinization enthalpy, peak temperature and retrodradation percentage of waxy maize flours and starches.The environmental factors during grain filling have significant effects on waxy maize grain yield and starch qualities. The plants grown in2013have higher grain yield and higher peak viscosity, gelatinization enthalpy and peak temperature of flours and starches, while retrogradation percentage response to environment during grain filling was dependent on variety and sown date. The underlying reason is the plants grown in2013have higher starch content and lower iodine binding capacity. The differences between two years were due to the plants have no effective rainfall during grain filling both for spring sown and summer sown maize in2012, in addition, the plants also suffered waterlogging and lodging at late grain filling stage for spring sown maize and suffer waterlogging between seedling stage and flowering stage for summer maize in2012. The results from pot, pool and field trials indicated that the waxy maize starch have higher peak viscosity, trough viscosity, breakdown and final viscosity and lower pasting temperature than the flours. Due to the waxy maize starch could absorbed more water, the gelatinization enthalpy was higher and gelatinization temperature lower than flours, while the difference of retrogradation percentage was dependent on varieties, which afford the basis to select variety based on utilization.