| Since the implementation of the super rice breeding program,the super hybrid indica rice has achieved an average yield breakthrough of 700,800,900,1000,1067kg/667m2 in the hundred acres demonstration field,leading the development direction of China’s super rice,providing a favorable guarantee for China’s Food security.With the increase of yield potential,how to change the quality of super hybrid indica rice has received widespread attention.At present,the rice planting model characterized by high nitrogen input has a negative effect on rice quality while increasing the yield.In addition,the grain filling period is an important period for the formation of rice yield and quality,and the final products starch and protein of carbon and nitrogen metabolism are the key factors affecting the quality of rice,and with the increase of nitrogen fertilizer application,the relationship between the filling characteristics of super hybrid indica rice and the quality of rice is also to be studied.In this article,selecting the representative varieties of super hybrid indica rice with different yield potentials: Liangyoupeijiu,Y Liangyou 1,Y Liangyou 2,Y Liangyou 900 and Xiang liangyou 900,and setting six nitrogen fertilizers: N0(control),N10,N14,N20,N26 and N30.The design of the split zone was carried out.The changes of grain grouting characteristics and rice quality of the super hybrid Indica rice under different nitrogen application were studied in 2016 and 2017 at Xinyang Pingqiao District test base.The main results are as follows:(1)Grain filling: On the grouting type,the relative grade of filled grain of super hybrid indica rice showed "V" type as a whole,which belongs to asynchronous grouting type,among which the asynchronous grouting of the large spike variety Y Liangyou 2 is the most obvious.The superior grains grouting started quickly and the time was early,grain weight entered the rapid growth period about 5 days after the flowering,the inferior grain grouting started slowly,the time was late,and the grain weight was after 10 days of flowering,it entered a period of rapid growth.The time at which the superior granules reach the maximum filling rate is earlier than the inferior granules,but the effect on the actual yield was smaller than that of the inferior granules.Y Liangyou 2 and Y Liangyou 900 had the fastest grouting speed,grain weight basically entered the platform period around 22 days after flowering,and Liangyoupeijiu,Y Liangyou 1 and Xiang liangyou 900 were enter the platform period around 29 days after flowering.The time to reach the maximum grouting rate moves back as the amount of nitrogen application rate increases,the maximum grouting rate decreases gradually,the grouting curve is relatively flat,the grouting rate is relatively stable,and the grouting active period is prolonged.With the increase of nitrogen application rate,the filling rate of superior and inferior grains gradually decreased in the early stage of grain filling(before 20 days after flowering),and gradually increased in the late stage of filling(20 days after flowering).(2)Processing quality: The processing quality of Y Liangyou 2,Y Liangyou 900 and Xiang liangyou 900 is better than that of Liangyoupeijiu and Y Liangyou 1.With the increase of nitrogen application rate,the processing quality has been improved.According to the head rice rate,the suitable nitrogen application rate of Liangyoupeijiu and Xiang liangyou 900 is N20 and N10,respectively,and the suitable nitrogen application rate of Y Liangyou 1,Y Liangyou 2 and Y Liangyou 900 is 210kg/hm2.(3)Appearance quality: The chalkiness degree and chalkiness grain rate of Liangyoupeijiu and Xiang liangyou 900 were significantly higher than that of Y Liangyou 1,Y Liangyou 2 and Y Liangyou 900.With the increase of nitrogen application rate,chalkiness degree and chalkiness grain rate decreased gradually,and the decrease gradually decreased.About the grain shape,with the increase of yield potential,the grain length and aspect ratio of the five varieties increased first and then decreased,and Y Liangyou 1 and Y Liangyou 2have the most slender grains.With the increase of nitrogen application rate,the grain length-width ratio and length showed a tendency of increasing first and then decreasing,and the longest at N20 level.The grain length and aspect ratio were negatively correlated with chalkiness.The chalkiness was used as the main indicator to measure the appearance quality,the suitable nitrogen application rate of the super hybrid indica rice was concentrated under the level of medium nitrogen(210kg/hm2—300kg/hm2).(4)Eating quality: The amylose content,setback and consistence viscosity of Liangyoupeijiu and Xiang liangyou 900 were higher than Y Liangyou 2,Y Liangyou 1 and Y Liangyou 900,and the peak viscosity and breakdown were lower than Y Liangyou 2,Y Liangyou 1 and Y Liangyou 900,so taste quality is poor.With the increase of nitrogen application rate,the peak viscosity,trough viscosity,breakdown and final viscosity generally decreased,and the absolute value of the setback decreased first and then increased,the change of consistence viscosity was relatively small.Taking the setback as the main indicator to measure the quality of eating,the suitable nitrogen application rate of the super hybrid indica rice was 150kg/hm2—210kg/hm2.(5)Nutritional quality: The protein content from high to the bottom of the super hybrid indica rice was Liangyoupeijiu,Y Liangyou 1,Xiang liangyou 900,Y Liangyou 900 and Y Liangyou 2,and the total content of essential amino acids was from high to low was Y Liangyou 1,Xiang liangyou 900,Y Liangyou 2,Y Liangyou 900 and Liangyoupeijiu.In general,the nutritional quality of Liangyoupeijiu is relatively poor.The protein content and essential amino acid content increased with the increase of nitrogen application rate.Taking the protein content and the total content of essential amino acids as the main indicators,the suitable nitrogen application rate of the super hybrid indica rice was 210kg/hm2—300kg/hm2.(6)Principal component analysis: With the increase of yield potential,the improvement of cooking quality and appearance quality should be paid attention to firstly,and the setback and grain aspect ratio were taken as the main indicators to measure the comprehensive quality of rice.On this basis,the improvement of nutritional quality and processing quality should be considerd.However,the grain length/width ratio is too high,which will also adversely affect the processing quality of rice.(7)Correlation analysis: There was a positive correlation between the time to reach the maximum grouting rate and the maximum grouting rate and the actual yield,and the effect of the inferior grain on the yield was greater than that of the superior grain.The time to reach the maximum grouting rate was a significant positive correlation with the head rice rate,grain aspect ratio,protein content,essential amino acid content and setback.The maximum filling rate was negatively correlated with head rice rate,protein content and setback.The maximum grain filling rate of superior grains was negatively correlated with essential amino acid content.The maximum filling rate of inferior grains is positively correlated with essential amino acids.Based on the above results,the appropriate amout of nitrogen fertilizer will delay the maximum filling rate of the super hybrid indica rice,the maximum filling rate will be reduced,and the grouting will be more stable,especially large spike varieties,which is conducive to the accumulation of starch and protein in the grain.It not only improves the filling degree of inferior grain,but also increases the grain aspect ratio and reduces the absolute value of the setback,which has certain positive effects on improving yield and improving rice quality.However,further research is needed on the complete synchronization of the high yield and high quality of the super hybrid indica rice. 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