| Magnaporthe oryzae,formerly known as Magnporthe grisea,is a filamentous fungus that represents a major gramineous pathogen that could fully devastate rice crops all over the world.The disease management practices for rice blast include the use of resistant cultivars,fungicides,proper nitrogen management,and the prevention of moisture stress.Using blast-resistant rice cultivars is considered the most effective option.However,as the M.oryzae is an easy variation pathogen,when the new races of M.oryzae occur the resistance can become ineffective.The study of pathogen population will contribute to find out the variation features and tendency of M.oryzae.And also I expect it would be helpful for the plant breeders to develop rice cultivars with durable resistance to rice blast disease.Pathogenicity structures of a rice blast fungus population,which is composed of two subpopulations,one consists of 98 isolated derived from japonica rice and another consists of 113 isolates derived from indica rice in 2012,were characterized with three sets of differential cultivars constructed in China,Japan,and LTH NILs.By the three differential sets,6,34 and 16 physiological races were determined in subpopulation with the diversity indices of 0.8979,0.8212 and 0.8178,respectively,while 7,24 and 15 physiological races were determined in with the diversity indices of 0.9012,0.8595 and 0.8502.Genetic structure of the two subpopulations was characterized by the Pot2-rep-PCR.115 indica rice and 106 japonica rice isolates were separated into 40 genetic lineages at the similarity coefficient of 75%.Among the 40 lineages,23 and 17 lineages were detected in Indica rice and Japonica rice subpopulations,and the dominant lineage L39 with a frequency of 28.31%was all consisted of indica rice isolates and another dominant lineage L31 with a frequency of 21.27%was all consisted by japonica rice isolates.In particular,there is no lineages consisted by isolates from both subpopulations.By comprehensive analysis,that isolates from indica rice and japonica rice were different in both pathogenicity and genetic structure which means they were significantly different in heterogeneity.1341 M.oryzae strains isolated from multispecies rice in Ganyu were identified into 51 monotypes by Pot2-rep-PCR and setted the similarity at 75%and 40%,the genetic diversity of the tested strains can be categorized into 45 and 17 lineages.The frequencies of dominant lineages under 75%similarity L3 was 36%.147 M.oryzae strains isolated from multispecies rice in Ganyu were identified into 11 monotypes by Pot2-rep-PCR and setted the similarity at 75%and 40%,the genetic diversity of the tested strains can be categorized into 8 and 6 lineages.The frequencies of dominant lineages under 75%similarity L1 was 48.03%.66 M.oryzae strains isolated from multispecies rice in Jintan were identified into 7 monotypes by Pot2-rep-PCR and setted the similarity at 75%and 40%,the genetic diversity of the tested strains can be categorized into 7 and 2 lineages.The frequencies of dominant lineages under 75%similarity L1 was83.33%.237 M.oryzae strains isolated from multispecies rice in Ganyu were identified into 47 monotypes by Pot2-rep-PCR and setted the similarity at 75%and 40%,the genetic diversity of the tested strains can be categorized into 34 and 29 lineages.The frequencies of dominant lineages under 75%similarity L1 was42.19%.Comparision between the diversity under 75%and 40%similarity shows that even the M.oryzae had a rich genetic diversity,the hereditary difference was not obvious.The correlation analysis of the monotypes of the M.oyzae showed a high correlation.The four M.oryzae groups and the M.oryzae from indica rice were identified by Pot2-rep-PCR and setted the similarity at 75%,the four groups isolates and the indica rice isolates didn't have a same lineage which showed that they were significantly different in heterogeneity.In conclusion,M.oryzae collected from the same multispecies rice area in different years which had a large difference in the quantity showed a high correlation,weinferred that the variation of the M.oryzae was limited. |
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