| Pursuit of high-quality and high-yield rice production is of great significance in ensuring China's food security,rice quality and rice competitiveness.Rice quality is a comprehensive trait,mainly influenced by genotypes,cultivation and some other aspects.Soft rice is a variety of rice with amylose content of 2-15%.Because of the low amylose content,soft rice has the advantages of being soft and not bad,sweet and refreshing,hard to harden after cold,small degree of retrogradation,etc.Soft rice quality is very popular with consumers,especially those in the middle and lower reaches of the Yangtze River.Recent years,a large number of high-quality soft rice varieties have been bred in the main rice-producing areas of China,such as in Jiangsu province.The varieties such as Nanjing 9108,Nanjing 5055,Suxiangjing 100,and Nanjing 46 have been widespread promoted in the whole province due to high yield potential and good taste quality.With the rapid increase of extension area in the whole province,followed by the non-matching of the protective cultivation measures,a series of production problems exposed,such as reduced of yield and worsen of cooked rice quality.These problems need to be solved by the study of cultivation measures.To deal with the issues above,the most widely popularized japonica soft rice varieties Nanjing 9108 and Nanjing 5055 in the central Jiangsu Province were used in this experiment,setting three cultivation measures which were the most commonly used measures in the process of cultivation,including different nitrogen level,different nitrogen management and sowing date,to research out the objective law of yield and rice national standard quality of Nanjing 9108 and Nanjing 5055 under these cultivation measures,and clarify the mechanism of relationships between starch quality and cooking quality under different cultivation measures.The experiments of nitrogen level and nitrogen management were carried out in 2014-2016 years at the base of Haian,Jiangsu province,the experiment of sowing date was carried out in 2016-2017 years at the base of Yangzhou University.The most widely popularized japonica soft rice varieties Nanjing 9108 and Nanjing 5055 in the central Jiangsu Province were used in this experiment.The nitrogen level experiment was including non-nitrogen,150,187.5,225,262.5,300,337.5 kg/hm2 respectively,the nitrogen management experiment was including 9:1,7:3,6:4 respectively,the sowing date experiment was including 5/21,5/26,5/31,6/5,6/10,6/15 respectively.Our main research content were the effects of yield and its compositions,processing quality,appearance quality,nutritional quality,cooking quality and structural characteristics and gelatinization characteristics of starches under different nitrogen levels,nitrogen managements,sowing dates.The main results are as follows:1.The effects of nitrogen levels on the yield and quality of Nanjing 9108 and Nanjing 5055:(1)The yield of two varieties increased first and then decreased with the increasing nitrogen level,the numbers of spikes increases first and then decreases with the increasing nitrogen level,the numbers of grains per panicles increased with the increasing nitrogen level,the total amount of spikelets increased first and then decreases with the increasing nitrogen level,seed setting rate and 1000-grain weight decreased with the increasing nitrogen level.The highest yield of two varieties can be obtained at the nitrogen application of 280kg/hm2.(2)The brown rice rate,milled rice rate and head rice rate increased with the increasing nitrogen level,the processing quality was improved;chalkiness rate and chalkiness degree increased first and then decreased,the appearance quality improved first and then decreased;the protein content increased by the increasing nitrogen level,nutritional quality improved;amylose content and gel consistency decreased with the increasing nitrogen level;the aroma,luster,taste,texture and taste value of cooked rice decreased with the increasing nitrogen level,while integrity of cooked rice increased with the increasing nitrogen level.The taste value decreased with the increasing nitrogen level appears two stage,a relatively slow decrease under the condition of 0?262.5 kg/hm2 and a rapidly decrease when the nitrogen application more than 262.5 kg/hm2.Therefore,considering yield and cooking quality,nitrogen application amount coordinated by yield and quality of Nanjing 9108 and Nanjing 5055 was 270 kg/hm2.2.The effects of nitrogen levels on structure and physicochemical properties of starches of Nanjing 9108 and Nanjing 5055:(1)Amylose content of two varieties decreased with the increasing nitrogen level;large particles of starch granules decreased with the increasing nitrogen level,while small and medium particles of starch granules increased with the increasing nitrogen level;crystal type of starches weren't changed by different nitrogen level,however relative crystallinity was found increased by increasing nitrogen level;the ordered structure of starch near the granule surface decreased with the increasing nitrogen level.(2)Solubility and swelling power increased with the increasing nitrogen level;peak viscosity,trough viscosity,breakdown viscosity and final viscosity increased by the increasing nitrogen level,while setback viscosity decreased by the increasing nitrogen level;gelatinization enthalpy,retro gradation enthalpies and retrogradation percentage all decreased by nitrogen level,it showed that increasing nitrogen level could improve the retrogradation of starch.Therefore,increase nitrogen level can improve starch gelatinization characteristics.3.The effects of nitrogen management on the yield and quality of Nanjing 9108 and Nanjing 5055:(1)The yield of Nanjing 9108 and Nanjing 5055 increased with the increasing of panicle fertilizer proportion,but showed no significant differences when the proportion of basal tiller fertilizer and panicle fertilizer were 7:3 and 6:4,the numbers of spikes decreased with the increase of panicle fertilizer proportion,the numbers of grains per panicles increased with the increase of panicle fertilizer proportion,the total amount of spikelets increased with the increase of panicle fertilizer proportion,seed setting rate and 1000-grain weight increased with the increase of panicle fertilizer proportion.(2)The brown rice rate,milled rice rate and head rice rate increased with the increase of panicle fertilizer proportion,the processing quality was improved;chalkiness rate and chalkiness degree increased with the increase of panicle fertilizer proportion,the appearance quality decreased;the protein content increased with the increase of panicle fertilizer proportion,nutritional quality improved;amylose content and gel consistency decreased with the increase of panicle fertilizer proportion;the aroma,luster,taste,texture and taste value of cooked rice decreased with the increase of panicle fertilizer proportion,while integrity of cooked rice increased with the increase of panicle fertilizer proportion.Taste value significantly decreased when the proportion of basal tiller fertilizer and panicle fertilizer was 6:4 compared with the proportion of basal tiller fertilizer and panicle fertilizer was 7:3.Therefore,the comprehensive consideration of production and quality,nitrogen management coordinated by yield and quality of Nanjing 9108 and Nanjing 5055 was 7:3.4.The effects of nitrogen management on structure and physicochemical properties of starches of Nanjing 9108 and Nanjing 5055:(1)Amylose content of two varieties decreased with the increasing of panicle fertilizer proportion;large particles of starch granules decreased with the with the increasing of panicle fertilizer proportion,while small and medium particles of starch granules increased with the increasing of panicle fertilizer proportion;crystal type of starches weren't changed by different nitrogen management,however relative crystallinity was found increased by with the increasing of panicle fertilizer proportion;the ordered structure of starch near the granule surface decreased with the increasing of panicle fertilizer proportion.(2)Solubility and swelling power increased with the increasing of panicle fertilizer proportion;peak viscosity,trough viscosity,breakdown viscosity and final viscosity increased with the increasing of panicle fertilizer proportion,while setback viscosity decreased with the increasing of panicle fertilizer proportion;gelatinization enthalpy increased with the increasing of panicle fertilizer proportion,while retrogradation enthalpies and retrogradation percentage decreased with the increasing of panicle fertilizer proportion,it showed that increasing the panicle fertilizer proportion could improve starch gelatinization characteristics.5.The effects of sowing date on the yield and quality of Nanjing 9108 and Nanjing 5055:(1)The yield of Nanjing 9108 and Nanjing 5055 decreased with the delay of the sowing date,the numbers of spikes,the numbers of grains per panicles,the total amount of spikelets,seed setting rate and 1000-grain weight all decreased with the delay of the sowing date.With a large area of production of 650kg per mu as a standard,the suitable sowing date of yield for Nanjing 9108 was first sowing date,second sowing date and third sowing date,the suitable sowing date of yield for Nanjing 5055 was first sowing date and second sowing date.(2)The brown rice rate,milled rice rate and head rice rate decreased with the delay of the sowing date,the processing quality was degradation;chalkiness rate and chalkiness degree decreased with the delay of the sowing date,the appearance quality improved;the protein content decreased with the delay of the sowing date,nutritional quality degradation;amylose content and gel consistency increased with the delay of the sowing date;the aroma,luster,taste,texture and taste value of cooked rice increased with the delay of the sowing date,while integrity of cooked rice decreased with the delay of the sowing date.The delay of the sowing date has improved the quality of cooked rice.Therefore,delay sowing date appropriately can achieve the coordination of yield and cooked rice quality.6.The effects of sowing date on structure and physicochemical properties of starches of Nanjing 9108 and Nanjing 5055:(1)amylose content of two varieties increased with the delay of the sowing date;large particles of starch granules increased with the delay of the sowing date,while small and medium particles of starch granules decreased with the delay of the sowing date;crystal type of starches weren't changed by different sowing date,however relative crystallinity was found decreased with the delay of the sowing date;the ordered structure of starch near the granule surface increased with the delay of the sowing date.(2)Solubility and swelling power decreased with the delay of the sowing date;peak viscosity,trough viscosity,breakdown viscosity and final viscosity decreased with the delay of the sowing date,while setback viscosity increased with the delay of the sowing date;gelatinization enthalpy decreased with the delay of the sowing date,while retrogradation enthalpies and retrogradation percentage increased with the delay of the sowing date,it showed that delay of the sowing date could induce degeneration starch gelatinization characteristics.In summary,increasing nitrogen level could increase the yield of Nanjing 9108 and Nanjing 5055,while excessive nitrogen level also reduces yield.Increasing nitrogen level could increase protein content,it is disadvantage to cooked rice quality,but decreased amylose content could improve the starch gelatinization characteristics.When the nitrogen application was 270kg/hm2, Nanjing 9108 and Nanjing 5055 had a slow reduce of cooked rice quality,a higher yield,so had a coordination of yield and cooked rice quality.When the nitrogen application was 270kg/hm2,increase the panicle fertilizer proportion can increase yield.When the proportion of basal tiller fertilizer and panicle fertilizer were 7:3 and 6:4,two varieties obtained the highest yield and get the better starch gelatinization characteristics.But when the proportion of basal tiller fertilizer and panicle fertilizer was 6:4,protein content increased significantly,caused degeneration in cooked rice quality.Therefore,when the proportion of nitrogen fertilizer operation was 7:3,Nanjing 9108 and Nanjing 5055 can achieve the coordination of yield and cooked rice quality.The yield of Nanjing 9108 and Nanjing 5055 decreased with the delay of the sowing date,and starch gelatinization characteristics became worse,but the reduction in protein content could improve the cooked rice quality.Hence,delay sowing date appropriately can achieve the coordination of yield and cooked rice quality.The above results can be used as a reference for Nanjing 9108 and Nanjing 5055 to select matching nitrogen level,nitrogen management,sowing date in the middle of Jiangsu.These results can be used as technical guidance for Nanjing 9108 and Nanjing 5055 planted in the middle of Jiangsu. |
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