| Rice is an important food crop.Rice blast ranks first of three major diseases in rice.At present,the rice varieties that widely planted in China are generally poor in resistance to disease,and rice blast disease occurs year after year with serious losses.It is the most economical and effective way to control rice blast disease by breedinging new rice varieties with good resistance to rice blast.Dalixixiang is a high-quality rice variety(line)improved from the Dalixiang which was breeded by the Rice Research Institute of Guizhou University.Improving disease resistance and yield of Dalixiang were the breeding target,and its rice quality has reached class 1 according to the national standards.Although the Dalixixiang has a certain increase in disease resistance compared with Dalixiang,the effect is not obvious.In order to further improve its resistance to rice blast,in this study,the Pi1 and Pi9 gene polymeric material/Dalixixiang//Dalixixiang BC1F4 populations constructed in the early stage of the research group were used as research materials,to conduct backcross generation of plants containing binary resistance genes in the population.BC1F6,BC2F2 and BC3F1 plants were obtained by combination of background recovery screening and agronomic traits investigation.Ten rice blast fungus strains from the main rice region of Guizhou were used for artificial inoculation in the field to evaluate resistance improvement effect in Dalixixiang.Combined with the investigation of agronomic traits,detection of background recovery,and identification of field resistance,intermediate materials with significantly improved resistance to rice blast,excellent agronomic traits,and high similarity to the genetic background of Dalixixiang were screened,aims to provide reference and materials for rice disease resistance breeding in Guizhou Province,and finally breeding a new rice variety(line)with high quality,broad spectrum and high resistance.The results were as follows:1.In the present study,markers RM224 and p B8 closely linked to the Pi1 and Pi9 genes were used to screen 20 backcross populations.Among them,7 plants with BC3F1,13 plants with BC2F2,and 6 stable BC1F6 strains.The background response rate of 50 pairs of polymorphic SSR markers was analyzed.The results showed that the average background recovery rate of BC3 plants was 88.86%,and the variation ranged from 84% to 95%.The background recovery rate of 5-2-5 was higher;the background recovery rate of BC3 plants was 81.46% on average,and the change range was between 74% and 87%.The background recovery rate of 26-7-5 plants was higher;The average response rate was 67.43% of BC1 plants,and the change range was between 62% and 72%.The background recovery rate of single plant 77 was higher.The above three plants were all from different generations of the same pedigree.2.Through the cluster analysis of the agronomic traits and grain appearance traits of the screening plants,it can be seen that the phenotypes of BC3F1 single plants 5-2-5and BC2F2 generation plants 26-7-5 are closer in appearance performance.In the reincarnation of the large grains of incense.Among them,the single plant 5-2-5 with a high similarity(95%)to the genetic background of Dalixixiang has the characteristics of the leaves of light and light,and the grain width of the grain is significantly higher than that of Dalixixiang.There was no significant difference between changhe 1000 grain weight and Dalixixiang.In the agronomic traits of the field,the grain height was higher than that of Dalixixiang,which was 1.9cm higher than that of the Dalixixiang,and the difference between the effective tiller and the Dalixixiang was 2 ears.The difference between the panicle length and the Dalixixiang was 2.4cm.The number of grains differs from that of the Dalixixiang by 873 grains.However,the background recovery rate of 26-7-5 per plant was 87%.It had the characteristics of the leafy leaves and photoperiods of the Dalixixiang: the grain appearance traits were significantly higher than 1000-grain weight,and the grain length and grain width were large.There was no significant difference in river incense.On the agronomic traits in the field,the plant height was higher by 9.3 cm than that of Dalixixiang,and the effective tiller was different from that of Dalixixiang by 2 spikes.The differencebetween panicle length and Dalixixiang was 0.4cm,and the number of individual plants was larger.There are 24 more sweets.3.Plants with binary resistance gene polymorphism exhibited higher levels of resistance to leafhoppers,with a disease grade of about 0.73,and most of the diseased leaf parts showed needle-like brown spots.The panicle blast also played a significant improvement effect.Although the panicles were susceptible,the incidence was lighter,and the loss index was about 79.4 percentage points lower than that of the large grain plume.Comprehensive evaluation between the middle resistance and the middle sensibility,relative to the Dalixixiang decreased by 4 to 6 disease levels.Plants carrying binary resistance genes showed large differences in phenotypes and genotypes between generations,but showed relatively stable resistance to rice blast.Binary resistance gene polymorphism could significantly increase rice blast resistance of Dalixixiang.4.At present,the breeding work has been carried out to the BC4F1 generation,and 2 plants carrying the Pi1 and Pi9 genes have been screened and obtained.Through field artificial inoculation,0.2,70.6% of the inoculated spikes of leaf carp appeared to be susceptible and the loss index was 15.3.%,its overall evaluation was moderate,and its appearance and background replies are for further study.5.It can be seen from the changes in the genetic loci and appearance traits of the intergenerational plants that the background of the low-generation backcross material has a low recovery rate,and there is a large difference between the appearance characteristics and Dalixixiang.With the increase of backcross generations,the background response gradually increased,and the appearance of plants gradually turned towards the recurrent parent.The main manifestations were the increase in grain weight and grain size of the plants,and the appearance of Dalixixiang of Phenotypic characteristics of light leaves and light ray.The results of correlation analysis showed that the background recovery rate was negatively correlated with plant height and effective tillering,and the correlation coefficients were-0.3 and-0.141,respectively;and there was a very significant positive correlation with grain length,grain weight,and aperture width,and the correlation coefficients were0.516**.,0.538**,0.511**;positive correlation with panicle length,number ofpanicles per panicle,grain width,light leaves,Pearson correlation coefficient were0.036,0.157,0.235,0.345,respectively.6.Rapid detection of Pi1 and Pi9 binary resistance genes in backcross populations can be achieved using multiplex PCR.The SSR marker RM224 has co-dominant detection of the Pi1 gene,while the STS marker p B8 can only positively detect the Pi9 gene. |
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