Identification And Genetic Mapping Of Rice Blast Resistance In Japonica Rice Germplasm Resources In Cold Region

Rice is one of the main crops,and almost half of the population in the world regards rice as their staple food.Rice blast is the main disease which will restrict the quality,stable yield and high yield of rice.The practice has proved that the breeding and utilization of rice blast resistant cultivars is the most effective measurement to prevent the rice blast.However,the physiological races of Magnaporthe grisea have genetic diversity and complex field population structure,which will produce pathogenic differentiation easily,and then result in the loss of resistance to some rice varieties after 3 to 5 years.Therefore,to comprehend the types of pathogens of rice blast and its pathogenicity timely,to make sure the rice blast resistance of the existing rice cultivars and the resistant genes' distributions,are very important in breeding of resistant rice cultivars,proper distribution and prolonging the use.To identify new resistant genes will extend the germplasm sources of rice blast resistance,and enrich the breeding materials of rice blast resistance.In this study,the rice blast fungi collected from different rice cultivated regions of Heilongjiang Province were identified in 2013 and 2014.To make sure the composition of physiological races of rice blast and filter out the physiological races with strong pathogenicity in Heilongjiang Province.In order to clarify the distribution of the disease resistance genes,a total of 225 rice varieties in Heilongjiang Province were screened by functional molecular markers of eight rice blast resistance genes.It provided the evidence for the improvement of the resistance of cultivars and the matching of the resistant parents.The rice blast resistance gene was mapped using F2 and RIL populations derived from Dongnong 415 and LTH by natural inducement and artificial inoculation of pathogenic strain.In order to obtain the main resistance gene of rice blast,and provide the theoretical and material basis for the breeding of rice blast resistance varieties in Heilongjiang Province.The main findings of the study are as follows:1.Utilize the 7 unified differential hosts in China,to identify the 172 rice blast strain collected from rice cultivated regions in Heilongjiang Province from 2013 to 2014.According to the naming standard of physiological races of rice blast,the population could be divided into 7 subpopulations and 42 physiological strains.ZD group and ZA group are the dominant populations,and the proportion of two groups were 36.05% and 35.47% respectively;The dominant strain was ZD5,its frequency was 19.77%.2.By the identification of seedling resistance,14 varieties with wide spectrum of resistant were screened out,which included 2~7 rice blast resistance genes.They are good resistance source materials for rice blast resistance breeding.In this paper,the resistance of varieties in this test showed an upward trend with the increase of the number of resistant genes.3.The results of varieties combined resistance analysis showed that: Suijing12 + He Jiang23,Dongnong415 +Longjing 31 and Dongnong415 + Mudanjiang26,etc.These 29 combinations were the better ones in preventing rice blast in the rice production.Dongnong 415 combined with other 9 materials were better than the others,and could provide a high resistance of rice blast.4.To utilize dominant ZD5 which had a better sporulation,a higher purity and a stronger pathogenicity to process the genetic analysis of rice blast resistant genes.Results showed that F1 were all resistant to blast,resistance of F2 and susceptible of F2 were coincide with the segregation regularity of 3:1.It showed that the resistance of Dongnong 415 to ZD5 was controlled by dominant gene.5.Rice blast resistance gene identification was executed on the basis of BSA.The preliminary resistant gene of Dongnong 415 to ZD5 was located on chromosome 7 between RM5426 and RM3552.The genetic distances were 2.1 c M and 1.6 c M respectively.It was named Pi-dn2(t).6.By the QTL analysis of leaf blast and neck blast level in tested RIL population,22 QTLs were identified under artificial inoculation and natural inducement.13 QTLs controlled YBLD and 9 QTLs controlled SBLD.Among them,q YBLD6-2,q YBLD7-1,q SBLD7-1,q SBLD6-1 and q SBLD10-1 were detected in different environments repeatedly,they were the loci which could express stably.q YBLD7-1,q SBLD7-1 and Pi-dn2(t)were all in the internal of RM420~RM336 on chromosome7,it was the new resistant gene loci identified in this study.