Screening Of High Quality Rice Germplasms With Strong Ratooning Ability And Evaluation Of Agronomic Performance Dissertation Dissertation

Ratoon rice is an important planting mode for increasing multiple cropping index and grain yield in rice region of south China.However,due to the lack of special varieties of ratoon rice in actual production,so it is urgent to screen rice germplasm resources with strong ratooning ability to promote the breeding of ratoon rice varieties.In addition,with the improvement of people’s living standards,consumers’demand for high quality rice is increasing.Further improvement of rice quality on the basis of high ratooning ability is of great significance to realize high yield and high quality cultivation of ratoon rice and to guarantee national food security.Therefore,based on the previous studies on the yield and ratooning ability of 75 rice materials from different countries and regions,this study selected 9 conventional rice germplasm materials with relatively high yield and ratooning ability in the ratoon season for the ratoon rice planting,and took Huang Huazhen（HHZ）,a variety widely used in the ratoon rice planting in central China,as the control.The purpose of this study was to compare the differences in yield,ratooning ability and rice quality of different rice germplasm materials,and to explore the physiological mechanism of the formation of strong ratooning ability.In order to provide a theoretical basis for the breeding of ratoon rice varieties.The main test results are as follows:（1）The yield of different rice germplasm materials in the main season and ratoon season showed significant differences.The yield of control material HHZ was 9.33 t ha^-1 and 4.94 t ha^-1 in the main and ratoon seasons,respectively.Among the other nine germplasm materials,the yield of CX17 was comparable to that of HHZ in main season,while the yield of W240,W085,IRIS＿313-8192 and CX119 was close to that of HHZ in ratoon season.IRIS＿313-10314 had the lowest yield of 4.25 t ha^-1 in the main season,and W200 had the lowest yield of 2.98 t ha^-1 in the ratoon season.The yield of other germplasm materials was at medium level.In the main and ratoon seasons,the higher yield of HHZ was mainly due to the increase of spikelets per panicle,total spikelets per unit area and total dry weight of shoot,while the lower yield of IRIS＿313-10314 and W200 was mainly due to the decrease of seed grain filling and harvest index.（2）The ratooning ability of different rice germplasm materials showed significant differences.Among the 10 germplasm materials,W200 had the strongest ratooning ability,up to 2.01,while CX119 had the weakest ratooning ability,only 1.29.CX121was also at a low level of ratooning ability（1.41）,but the rest of the germplasm materials were more than 1.50.The results of correlation analysis showed that there was a significant positive correlation between the ratooning ability of different germplasm materials and the total dry weight of stubble at harvest of main season.（3）There were significant differences in rice quality in the main and ratoon seasons among different rice germplasm materials.In terms of processing quality,the highest yield of milled rice in the main season was W269,the lowest was IRIS＿313-10314,the highest yield of milled rice in the ratoon season was IRIS＿313-8192,and the lowest was W200.In terms of appearance quality,IRIS＿313-8192 and HHZ had the lowest chalky grain rate and chalky degree in both the main and ratoon seasons,while the rest of the germplasm materials had higher chalky grain rate and chalky degree in both seasons.For cooking and eating quality,W085 showed high gel consistency,low amylose content and high taste value in both the main and ratoon seasons,while IRIS＿313-10314 showed the worst cooking and eating quality in both seasons,and the other germplasm materials showed a medium level of cooking and eating quality.In conclusion,among the 10 germplasm materials selected in this study,although W200 had the strongest ratooning ability,its yield in the main and ratoon seasons was low,and its rice quality in both seasons was poor.The ratooning ability of IRIS＿313-8192 was slightly lower than that of W200,but the yield of IRIS＿313-8192 was higher in the main and ratoon seasons,and the processing and appearance quality of IRIS＿313-8192 was the best in the two seasons,and the cooking and eating quality was in the middle level.Overall,the overall performance of IRIS＿313-8192 was closest to that of the control material HHZ.Therefore,the selection of germplasm resources of high ratooning ability and good quality rice should be considered comprehensively,and increasing total dry weight of stubble in the main season is an important basis for improving ratooning ability,while increasing spikelet number per panicle on the basis of high ratooning ability is an important way to achieve high yield in the ratoon season.