Identification Of Blast Resistance Of Improved Dalixixiang And Comprehensive Evaluation Of Rice Quality

Rice blast is one of the important diseases that affect the yield and quality of rice.The high-quality rice varieties currently promoted in Guizhou Province have weak resistance to rice blast.Therefore,the rice blast disease has become a restriction on improving yield,quality and application of high-quality rice varieties in our province.Breeding new rice varieties with broad-spectrum resistance is the most economical,green and environmentally-friendly way to control rice blast.The"Dalixixiang"in this study is a high-quality rice variety(line)bred by the Rice Research Institute of Guizhou University with"Dalixiang"as the background and the breeding goal of improving disease resistance.Its rice quality reaches the level of"Dalixiang".Although disease resistance has been improved to some extent,the effect is not obvious,In order to further improve its resistance to rice blast,the previously constructed polymeric rice material carrying Pi1 and Pi9 double genes was used as the donor parent and Dalixixiang was used as the receptor parent.The BC₅F₅population was obtained through multiple backcrossing and selfing,combined with molecular markers by means of assisted selection,83 lines containing resistance genes were obtained,and the resistance to rice blast,main agronomic traits and rice quality at different ecological points were studied.The main results are as follows:1.Using the SSR marker RM224 and STS marker p B8 closely linked to the Pi1and Pi9 genes,83 lines containing the resistance gene were screened in the selfed population.Among them,there were 17 lines containing the Pi1 gene and 23 lines containing the Pi9 gene.There are 43 lines with double genotypes.2.The indoor seedling blast resistance of Dalixixiang and its improved strains were identified.The results showed that the seedling blast of Dalixixiang was grade 7,while the improved strains were graded 2?6,among which the disease grade was 2?4grade,67 strains showing resistance,moderate resistance and moderate susceptibility,accounting for 80.7%.Compared with the susceptible control,the resistance of the 83strains selected by molecular marker-assisted selection was improved to varying degrees.3.The field identification results of Liping and Meitan identification nurseries showed that the control parent Dalixixiang in the two disease nurseries had leaf blast disease grades 8 and 7,and ear blast susceptibility was both grade 9,and its comprehensive resistance index was 8.4.It is highly susceptible to rice blast,indicating that the disease is fully affected in the field.The improved strains containing resistance genes have leaf blast disease grades of 1?7 in the two disease nurseries;the incidence rate of ear blast is 5?9,which is susceptible.Although most ears are susceptible,the loss rate of ear blast is disease grade.It is lighter,and the loss rate of ear plague of grade 8 in Dalixixiang is reduced by 3 to 7 grades compared with the control.Among them,53 improved strains had a comprehensive resistance index of 2.48?4.08,showing moderate resistance to rice blast;29 strains had a comprehensive resistance index of 4.10?6.04,showing moderate susceptibility.The resistance of the identified strain containing the resistance gene was significantly improved compared to the control parent.4.The brown rice rate,milled rice rate,perfect head rice rate,length to width ratio,grain length,chalk white degree,chalky grain rate,alkali fire value,gel consistency,straight chain starch content of 83 improved strains and Dalixixiang in Liping and Meitan two ecological environments Analysis and evaluation were made on 10 indexes.The results showed that the brown rice rate of the improved strain quality traits in the two ecological environments had the same rate of reaching the national high-quality rice standard,98.8%.The perfect head rice rate was 7.20%and43.36%in Liping and Meitan,respectively.The compliance rates of the straight chain starch content were 85.54%and 89.16%,the chalky grain rates were 55.43%and66.27%,the chalk white degree compliance rates were 26.51%and 38.55%,and the gel consistency compliance rates were 98.8%.It can be seen that the brown rice rate,the straight chain starch content and gel consistency are relatively stable quality traits,while perfect head rice rate,chalky grain rate and chalk white degree are environmentally sensitive traits.Therefore,increase the whole rice rate.Reducing the chalky grain rate and chalk white degree is still an important goal for rice quality improvement.5.Dalixixiang in the Meitan ecological environment is the national third-grade high-quality rice,but in Liping,it has not reached the high-quality rice standard,mainly because the whole rice rate has not reached the standard.In the two ecological environments of Liping and Meitan,there are 5 strains of improved strains that meet the national three-level quality rice standards,namely QHX37,QHX78,QHX135,QHX139 and QHX156,among which all quality indicators of strain QHX122 have reached National second-class quality rice standard.There are 9 strains with 6indicators reaching the national level 3 or above,namely QHX34,QHX44,QHX62,QHX101,QHX104,QHX118,QHX131,QHX183,QHX191.6.Comprehensive from three aspects of the identification results of rice blast resistance,main agronomic traits and rice quality indicators.The analysis results show that QHX34,QHX62,QHX78,QHX101,QHX118,QHX122,QHX183 and QHX191have little difference in agronomic traits and rice quality from Da Li Xi Xiang,and the resistance to rice blast has been significantly improved,which can be used as excellent Disease-resistant breeding materials.