| Rice blast caused by Magnaporthe oryzae is one of the most devastating rice diseases worldwide.The use of R genes is the most eco-friendly and sustainable approach for blast control.However,Magnaporthe grisea has a high degree of variability of physiological race and serious differentiation of pathogenicity,which led to loss of variety resistance only about 3-5 years after being application.In order to achieve broad-spectrum,durable resistance varietise,we should have deep research in rice blast fungus and analyse the composition of its physiological races.At the same time,we should identify and utilize of excellent broad-spectrum resistance genes which will be lead to the rice varieties or polymerized by means of multi-gene pyramiding.In this research,Magnaporthe grisea strains were collected and isolated from different ecological regions to analyze race’s composition and distribution and infection characteristics.One hundred and fifty eight single-spore isolates were obtained from diseased panicles,which were collected from ten ecological regions,including zhejiang,guangdong,anhui,guangxi,hainan,jiangsu,hubei,hunan,jiangxi,sichuan.Using 7 Chinese differential materials of rice,these isolates were inoculated in seedling stage.Results show that these single-spore isolates can be divided into 7 groups and 27 physiological races.And the distribution of these physiological races is region specific.For example,the predominant group is ZB in the southern indica rice region(guangdong,hubei,guangxi,jiangxi,sichuan);the dominant group are ZE,ZG and the predominant group are ZE1、ZG1 in the japonic rice region(jiangsu);There are more physiological race type in hainan,anhui and hunan than zhejiang,the predominant groups are ZA,ZB,ZC,ZG.In this study,we constructed a set of double gene pyramiding lines by means of hybridizing the near-isogenic lines(NILs)(Pigm,Pi2,Pi9,Pi40,Piz)constructed with Yangdao 6 as recurrent parent with near isogenic lines Pil,Pi33 and Pi54 respectively.At the same time we chose 2-4 rice plant whose agronomic traits similar to Yangdao 6 by whole genome sequencing(GBS)for detecting the back ratios of genetic background,the sequencing results based on the analysis,the choice of double gene pyramiding lines background response rate in more than 98.02%,distributed in 98.02%(Pi9+Pi1)-98.98%(Pi2+Pi33)in particular,retain the blast resistance gene of Yangdao 6 carried,and subsequent resistance based on the analysis of resistance on the genetic background.Under the conditions of artificial inoculation,there was a significant difference in the resistance effect among different gene combinations,and the resistance level of all gene cmbinations had been enhanced to different degrees in comparison with the recurrent parent Yangdao 6.The most effective resistant gene combinations were Pigm+Pil,Pigm+Pi33,Pigm+Pi54,Pi9+Pi54,Pi9+Pi1,Pi2+Pi1 and Pi2+Pi33 with their seedling blast and panicle blast resistance frequency was more than 90%.At the same time,we found that most gene combinations produce positive effect,only a small part of gene combination has a negative effect,such as Piz+Pi33 and Pi54+Pi33.In addition,the natural induction,only Pigm+Pi1,Pigm+Pi33 and Pigm+Pi54 in three nurseries was stable most,and the other combination of genes resistant effect is regional-specific and could be specifically applied in the target area.The survey of the agronomic trait shows that the double gene pyramiding lines system with Pi2 behave heading date in advance,less grain number per panicle and lower yeild.The others have no significant differences with their recurrent parent Yangdao6. |
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