Factors Affecting Grain Quality And Starch Physicochemical Properties Of Rice

In recent years,with the development of economy,Chinese government strengthens the supply-side structural reform of agriculture to improve the quality and efficiency of the agricultural supply system,and to ensure that the supply of agricultural products is sufficient.For this reason,rice as one of the main staple food crops for over half the global population,its improvement remains one of the main objectives of rice breeding programs.In this study,the main factors determining the sensory quality and physicochemical properties of rice was explored using both indica and japonica rice as materials.The main results are summerized as follows:1.The sensory quality and physicochemical properties of three japonica rice cultivars harvested in two different growing locations(Xiangshui and Hangzhou)were compared to determine the most important factors affecting the sensory quality.All three cultivars had higher scores for overall sensory quality when grown in Xiangshui compared with Hangzhou,indicating that the growing location is a key factor in determining the sensory quality of cooked japonica rice.In addition to growing location,cultivar(genotype)had an important effect:Longdao 18 scored the highest for overall sensory quality in two locations,whereas Longdao 30 had a lowest score in Xiangshui,and both Longdao 20 and Longdao 30 had the lowest scores in Hangzhou.Many physicochemical properties,such as apparent amylose content(AAC),protein content,thermal properties,and free amino acids showed significant differences between the two locations.Correlation analysis showed that gel hardness(HD)and protein content had contrasting effects on all the sensory attributes.The overall sensory quality was negatively correlated with protein content(r=-0.890,P<0.05)and positively correlated with HD(r=0.910,P<0.05),indicating that the protein content and HD are important physicochemical properties for predicting the sensory quality of japonica rice.2.Physicochemical and functional properties of endosperm starches form four mutants(JM1-4)and their indica parent 93-11 harvested in two different locations were characterized.JM1 and JM4 with white-belly had little higher AAC.JM1 showed little difference gelatinization temperature and pasting viscosities from 93-11,while JM4 showed higher gelatinization temperature and lower pasting viscosities.JM2 with white-core had much higher AAC,which also displayed much higher HD.JM3 with floury endosperm had little lower AAC,which also showed much higher fatty acid content and lower pasting viscosities.Correlation analysis showed the granule-bound starch synthasel(GBSSI)content was positively correlated with AAC(r=0.902,P<0.01)and HD(r=0.940,P<0.01)，and GBSSI was not be sensitive to environmental conditions;soluble starch synthaseⅢa(SSⅢa)was positively correlated with AAC,indicating that GBSSI and SSⅢa are important in affecting physicochemical properties of indica rice.