| The rice blast disease[Magnaporthe grisea(Hebert)Barr.,whose asexual generation is Pyricularia grisea(Cooke)Sacc.],one of the three major worldwide rice diseases caused by the rice blast fungus,has caused great economic loss in the rice production industry.Due to its various pathogenicity,wide cultivation of the disease-resistant rice variety will lead to the deprivation of its resistance capability.Therefore,in order to cultivate the persistently disease-resistant varieties and establish a more efficient policy as the good theory foundation for prevention and control,we should understand its pathogenicity,its mutational mechanism,the functions of the genes of avirulence and pathogenicity.In this research,inoculations in vivo and in vitro were used in 6 rice varieties of CO39 and its 5 near-isogenic lines of C101LACPi-1(t),C101AS1Pi-2(t), C104PKTPi-3(t),C101PKTPi-4a,C101TTP-4L-23Pi-4b and CO39.From the rice blast fungus' T-DNA insertion mutant bank,which was already constructed by ATMT (agrobacterium tumefaciens-mediated transformation)technology in the lab,three mutants of steady variation in their pathogenicity,that is,T940084602,T940017403,T940077801,were selected for the related pathogenicity analysis.The results showed that the 3 mutants had enhanced pathogenicity to C101LACPi-1(t)and C101PKTPi-4a.After the phenotype analysis,the mutants of enhanced pathogenicity had no significant difference with the wild type in the following aspects:its growing speed,spore quantity, spore germination rate,as well as the formation rate of its appressorium,from which it could be presumed that the T-DNA insertion probably did not have effects on the phenotype of these 3 mutants.The PCR result indicated that they all include the Hyglomychl Phosphtobamfemse gene.At the same time,the T-DNA flanking sequences of these 3 mutants were acquired by TAIL-PCR.Among the sequences,T940017403 is homologous with Supercontig183 719459 bp～720010 bp of the rice blast fungus genome.The T-DNA insertion locus is in the carbon region of the MGG.07908.5 gene,which encodes an unknown protein of Glycosyl hydrolases family 6.It was presumed that the transition of mutant pathogenicity to the rice variety of Pi-1(t)from avirulence to virulence was the result of the T-DNA insertion,which blocked the activeness of this protein.In addition,the mating-cultivation experiment and molecular surveillance proved that the mating type of the 3 mutants was MAT1-1,in which,the hygromycin-resistance ratio of the sexual F1 progenies of T940017403 and KA9 was proved to be 1:1.The phenotype of the mutant may be result from the single copy of T-DNA insertion,which established the foundation of the further clone and analysis of Pi-1(t)toxicity related genes. |
