| For a long time,the genetic relationship between Northern Japonica Rice in China and Japanese japonica rice is very close,the plant type and other agronomic characters are similar,and the cultivation techniques are also similar.Until the 1980s-1990 s,the erect panicle type of Japonica Rice in northern China,especially in Liaoning,was gradually popularized,the yield potential increased significantly,and the application amount of chemical fertilizer,especially nitrogen fertilizer,also increased significantly,while the plant type and application amount of Japanese japonica rice basically remained unchanged.In order to compare the agronomic characters of Japanese japonica rice varieties and Chinese Japonica Rice Varieties under different fertilization conditions,Japanese japonica rice representative variety Akitakomachi and Chinese japonica rice representative variety Liaogeng 5 were selected respectively.Akitakomachi is a representative high-quality variety of Japanese japonica rice,and Liaogeng5 is the first erect panicle type variety of Northern Japonica Rice in China.The representative Japanese Japonica Rice Variety Akitakomachi and the representative Chinese Japonica Rice Variety Liaogeng 5 were selected to construct recombinant inbred lines(RILs)and planted under different nitrogen application conditions.The differences of important agronomic characters were compared according to different panicle types.At the same time,RILs were sequenced and analyzed to draw accurate linkage maps,and R / QTLs were used(http://www.rqtl.org/)Identify QTLs of important agronomic traits and verify the effect expression of dpe1 under different nitrogen treatments by CRISPR / cas9 gene editing technology,in order to clarify the fertilization response of different types of Japonica rice varieties,which can provide useful information for new breeding strategies and cultivation for sustainable food security in the future.The specific research results are as follows:1.The effects of nitrogen fertilizer on plant type,panicle traits,yield and quality of rice with different panicle types were studied by different nitrogen fertilizer treatments on recombinant inbred lines with different panicle types.The results showed that nitrogen fertilizer had great effects on plant type,panicle traits,yield and quality.With the increase of nitrogen fertilizer,the plant types of recombinant inbred lines of each panicle type showed significant differences,including plant height,leaf length and leaf width,and plant height,inverted two-leaf width,inverted three-leaf length and inverted three-leaf width increased significantly with the increase of nitrogen fertilizer.Spike number,primary and secondary branch number,grain number per spike and grain density also increased,reaching significant or extremely significant level except grain number per spike,biological yield and theoretical yield all increased,and theoretical yield reached extremely significant level;However,with the increase of nitrogen fertilizer content,the seed setting rate showed a downward trend,and the milling quality,appearance quality and nutritional taste quality also decreased to varying degrees.2.The results of this study showed that the plant height,flag leaf base angle and leaf length of erect panicle type population were significantly lower than those of semi-erect and curved panicle type population under high nitrogen and low nitrogen treatments.The leaf width was significantly higher than that of the other two panicle types.With the increase of panicle curvature,the panicle length and 1000-grain weight increased,and the erect panicle type population was significantly less than the other two panicle types,and the number of panicles,grains per panicle,primary and secondary branches and grain density of the erect panicle type population were significantly or extremely significantly higher than the other two panicle types.However,the seed setting rate was significantly or extremely significantly lower than the other two panicle type populations.The biomass and theoretical yield of curved panicle type population were higher than that of erect and semi-erect population under high and low nitrogen treatments,and the quality of erect panicle type population was the worst under two nitrogen treatments.3.Using the strategy of map construction based on resequencing,the isolated population and its parents obtained from the cross between Akitakomachi and Liaojing No.5 were resequenced.A total of 639.74 GB of raw data were generated,and the depth of each RIL was about 7.88 times,the depth of Liaojing No.5 was 27.12 GB(61.00 times),and the depth of Akitakomachi was 21.28 GB(51.00 times).A total of 106,844 SNP were identified between parents.A recombinant bin map containing 970 recombinant fragments was constructed using69284 high-quality polymorphic SNP markers,with a total genetic length of 894.49 c M.Because the two parents belong to japonica subspecies,the marker density of chromosomes 2,3,6,8 and 9 is low,but scientific research still meets the needs of genetic mapping.The gene infiltration rate of Liaojing No.5 showed a normal distribution,which was significantly positively correlated with the number of grains per panicle under low fertilization conditions,while significantly positively correlated with 1000-grain weight and yield under high fertilization conditions.4.QTL mapping of 33 important agronomic traits,including plant type,ear traits,yield-related traits and quality traits in RIL population under high and low nitrogen treatments,42 QTL were detected in two environments,including 19 under low nitrogen treatments and23 under high nitrogen treatments.QTL controlling flag leaf width and inverted leaf width was also found on chromosome 1 under low nitrogen condition,and a QTL cluster was found on chromosome No.9.The QTL cluster on chromosome No.9 was related to plant height,panicle curvature,flag leaf length,inverted leaf length and inverted leaf width under high nitrogen condition.Further analysis showed that the QTL cluster overlapped with the known erect panicle type gene DEP1.Only 2 of the 11 QTLs related to ear traits detected under two conditions were stably expressed,accounting for only 18.2%.These two loci are located on chromosome No.9 to control the spike length gene and chromosome No.11 to control the number of primary branches.A QTL was detected on chromosome 1 for controlling grain density under low nitrogen condition,a QTL for affecting spike number on chromosome No.3under high nitrogen condition,a QTL for controlling 1000-grain weight on chromosome No.3,and a QTL cluster for affecting yield on chromosome No.3.QTL affecting brown rice rate was detected on chromosome No.11 under low nitrogen condition.It was found that whiteness value and protein content played a role on different chromosomes under different nitrogen fertilizer conditions.5.Combined with the related results on chromosome No.9 of QTL,we used CRISPR/Cas9 gene editing technology to carry out mutation experiments involving DEP1 under the genetic background of japonica rice variety Sasanishiki.The wild type and mutant were planted under high and low nitrogen modes.Compared with the wild type,the plant height,panicle curvature and taste value of the mutant were more sensitive to the change of nitrogen,while the grain number per panicle,panicle number,economic coefficient and yield of the mutant were relatively stable under different nitrogen conditions,which indicated that the DEP1 mutant showed improved rice quality without serious yield loss under different nitrogen conditions. |
PDF Full Text Request