Research On The Comparison Of Rice Quality Between Ratoon-Season Rice And Late-Season Rice

With the development of our society,people’s living standards are improving rapidly in recent years.High yield is no longer the only target of rice production,and people’s demand for high-quality rice is increasing gradually.Therefore,the cultivation of high-quality rice is one of the important research areas in our country’s future rice production.Rice ratooning,as an important strategy during the transition period of rice production in our country,has the advantage of short growth duration,high daily yield,low production cost and superior quality of rice in ratoon-season,which is conducive to farmers to get higher income when get higher yields of rice.Among the conventional rice cropping system in China,the quality of late-season rice is much better than that of early-season rice and middle-season rice.The mean air temperature during the grain filling period is one of the most important environmental factors affecting rice quality.In rice production,the heading date of ratoon-season rice and late-season rice is roughly the same,and the air temperature during filling stage is much lower,which is conducive to the formation of high-quality rice.However,it has not been reported whether there are differences between ratoon-season rice and late-season rice.Therefore,we conducted field experiments in Qichun country in 2018 and 2019,and Liangyou 6326,Fengliangyouxiang 1(two hybrid varieties with a large area of cultivation as ratoon rice in central China),and Huanghuazhan(an inbred variety only in 2019)were selected as experimental materials.We set up two cropping system,ratooning rice and late-season rice,with local high-yield management methods.In order to make the heading date of ratoon-season rice as the same as that of late-season rice,we set four sowing date treatments of late-season rice on 5th June,10th June,15th June,20th June in2018,and three sowing date treatments of late-season rice on 9th June,14th June,19th June and the main crop of rice ratoon with sowing date on 20th March in 2019,aimed to investigated the differences of rice quality between ratoon-season rice and late-season rice under the condition of the same temperature in filling period.Yield and its components,brown rice rate,milling rice rate,head rice rate,chalkiness rice rate,chalkiness degree,grain shape,gel consistency,amylose content,alkali spreading value were measured and calculated in both ratoon-season rice and single late-season rice.The main results were as follows:(1)The growth duration of ratoon crop of rice ratooning is 63-86 d,which was 52.1%-67.4%of the duration of late-season rice.But the total growth duration of main crop and ratoon crop is 58.1%-77.8%longer than that of late-season rice because of the longer growth duration of main crop.The heading date of ratoon crop is the same as that of late-season rice with sowing date S3(6th September)in 2018 and S1(28th August)in 2019.The yield of ratoon crop was18.1%-23.5%and 26.6%-43.7%less than that of late-season rice with the same grain filling period in 2018 and 2019,respectively.In both years,there was no difference in yield of late-season rice of same variety with different sowing dates.(2)Compared with late-season rice with the same temperature in filling stage,panicles per m~2of ratoon-season rice was significantly higher than that of late-season rice,but the number of spikelets per panicle and total spikelets per unit area of ratoon-season rice were much lower,which were mainly contributed to the lower yield of ratoon-season rice.In terms of dry matter accumulation,the lower yield in ratoon-season was mainly due to its less total aboveground dry weight compared with that of late-season rice.Meanwhile,harvest index of ratoon-season rice was higher than that of late-season rice in 2018,but it was opposite in 2019.There was no significant difference in yield components among late-season rice with different sowing dates in both years.(3)The rice quality of ratoon-season rice was significantly different from that of late-season rice when the grain filling stage was the same.Specifically,brown rice rate,milling rice rate and head milling rice rate of Liangyou 6326 and Fengliang Youxiang 1 in ratoon season were worse than that of late-season rice,with the difference of head milling rice rate being the most significant.But milling quality of Huanghuazhan in ratoon season did not show an obvious decrease.In terms of appearance quality,the chalkiness grain rate and chalkiness degree of ratoon-season rice were significantly higher than that of late-season rice in 2018,but there was no difference in 2019.And there were little differences in the ratio of grain length and grain width between ratoon-season rice and late-season rice.Regarding cooking quality,the amylose content of Langyou6326 in ratoon-season was significantly higher than that of late-season rice,but there were no differences in gel consistency and alkali spreading value between ratoon-season rice and late-season rice.Moreover,Fengliangyouxiang1 showed that the amylose content of ratoon-season rice was significantly lower than that of late-season rice with the same grain filling stage.And the gel consistency of ratoon-season was much higher,but there was no difference in the alkali spreading value.The difference in rice quality of late-season rice between different sowing date treatments is mainly reflected in the fact that the chalkiness grain rate and chalkiness degree of late-season rice at sowing date S2 in 2018 were significantly lower than at the other sowing date treatments,and the alkali spreading value of Liangyou 6326gradually increased with the delay of sowing date The amylose content of late-season rice of Fengliangyouxiang1at sowing date S1 was significantly lower than that of late-season rice at other sowing dates,and the gel consistency was significantly higher than that at other sowing dates.In addition,the head milling rice rate of late-season rice at sowing date S1 in 2019 was significantly higher than that of late-season rice at other sowing dates.Under the conditions of the experiment,the rice quality of ratoon-season rice was significantly different from that of late-season rice when the air temperature of the grain filling stage was the same.Compared with late-season rice,the milling quality of Liangyou6326 and Fengliangyouxiang1 in ratoon season was significantly lower,but Huanghuazhan had no significant difference between ratoon-season rice and late-season rice.The difference in chalkiness grain rice rate and chalkiness degree between ratoon-season rice and late-season rice was inconsistent in 2018 and 2019.In 2018,cooking quality related traits of Fengliangyouxiang1in ratoon season were better than those of late-season rice with the same heading date,but Liangyou6326 had no significant difference in related traits.In summary,the milling quality and appearance quality of ratoon-season rice are inferior to those of late-season rice with the same grain filling period,but rhe cooking quality of ratoon-season rice is much better,and the annual yield of ratooning rice is higher,which is conducive to ensuring our country’s food security.Variety improvement and optimization of cultivation management methods are important research directions for improving the quality of ratooning rice in the future.