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The conidia of Pyricularia oryzae were cultured on barley grain medium for 17 days in this study. Two hundred milliliters of barley grains of each tested strain were cultured in a 500 mL Erlenmeyer flask. The conidia were eluted with 300 mL of sterile water from the cultivated barley grains in each flask. The barley grains were placed in aluminum plates for continued cultivation. The conidia were eluted with 48 h of interval culture, and the elution method used each time was the same as that used for the first elution. All the tested strains could be eluted 6 times; thus, we obtained a large number of conidia. The numbers of conidia produced in the elutions of all the strains were significantly different, with the smallest number produced in the first elution, followed by a gradual increase and then a gradual decrease after reaching the peak; the number of conidia produced in the sixth elution, that is, the final elution, was also low. The total number of conidia and the total number of effective conidia differed among the strains. A large number of effective conidia can be obtained by using the method described in this study, and much time can be saved because the conidia can be eluted six times in one culture cycle. [ABSTRACT FROM AUTHOR]

The objective of this study was to preliminarily analyze the differences in pathogenicity and physiologic races between Pyricularia oryzae isolates from indica and japonica rice varieties. Five to 7 isolates of P. oryzae from indica and japonica, having good sporulation capacity, were screened out in each experimental year. To determine the pathogenicity of P. oryzae, different kinds of rice varieties were inoculated with mixtures of indica and japonica isolates. A total of 46 isolates, including 23 indica isolates and 23 japonica isolates, were screened out in four years. In total, 1252 rice varieties, including 490 indica, 296 japonica and 466 indica-japonica hybrid rice varieties, were inoculated. Our results suggested that the degree of disease was more severe in most indica varieties infected with indica isolates than in those infected with japonica isolates. That is, indica isolates were more inclined to infect indica varieties. A majority of japonica and indica-japonica hybrid rice varieties infected with japonica isolates showed more severe infection than those infected with indica isolates. In other words, japonica isolates more easily infected japonica and indica-japonica hybrid rice varieties. The differences in quantity among the varieties indicated high resistance to rice blast in the corresponding kinds of rice inoculated with indica and japonica isolates, fully explaining the above viewpoint. Most of the 23 indica isolates belonged to indica races. Among the 23 japonica isolates, half were indica races and half were japonica races. In addition, there were significant differences between the isolates selected in the first two years and those selected in the second two years. The isolates in the first two years were all of indica races, and those of japonica races all appeared in the second two years. The results showed that the race of isolates shared little association with the kind of rice variety collected but was associated with the year of neck blast sample collection. [ABSTRACT FROM AUTHOR]

Peroxisomes play important roles in metabolisms of eukaryotes and infection of plant fungal pathogens. These organelles proliferate by de novo formation or division in response to environmental stimulation. Although the assembly of peroxisomes was documented in fungal pathogens, their division and its relationship to pathogenicity remain obscure. In present work, we analyzed the roles of three Pex11 family members in peroxisomal division and pathogenicity of the rice blast fungus Magnaporthe oryzae. Deletion of MoPEX11A led to fewer but enlarged peroxisomes, and impaired the separation of Woronin bodies from peroxisomes, while deletion of MoPEX11B or MoPEX11C put no evident impacts to peroxisomal profiles. MoPEX11A mutant exhibited typical peroxisome related defects, delayed conidial germination and appressoria formation, and decreased appressorial turgor and host penetration. As a result, the virulence of MoPEX11A mutant was greatly reduced. Deletion of MoPEX11B and MoPEX11C did not alter the virulence of the fungus. Further, double or triple deletions of the three genes were unable to enhance the virulence decrease in MoPEX11A mutant. Our data indicated that MoPEX11A is the main factor modulating peroxisomal division and is required for full virulence of the fungus. [ABSTRACT FROM AUTHOR]

Abstract: Inoculation methods for rice blast fungus Magnaporthe oryzae to Brachypodium distachyon were developed to investigate the infection process and symptom development in comparison with those on rice (Oryza sativa) and barley (Hordeum vulgare). M. oryzae could infect leaves, sheathes, stems and panicles of B. distachyon and cause blast disease. Spraying conidial suspension on either intact seedlings or leaf segments induced typical symptoms on B. distachyon. During the intact seedling inoculation, the symptom developed on B. distachyon leaves closely resembled that on rice; but the lesions on B. distachyon had better uniformity in shapes and sizes than those on rice or barley. In the leaf segments inoculation, only initial and low-developed lesions could be found on rice, while normal symptoms on B. distachyon and barley. Inoculated with low-virulent mutants of M. oryzae, B. distachyon produced low-level symptoms. The symptom level of each mutant on B. distachyon corresponded well to that on rice. In addition, typical infection processes presented on B. distachyon leaves: forming melanized appressoria, penetrating into host epidermis and then forming hyphae in epidermal cells. According to these results, B. distachyon can be used as a candidate for studying fungus-plant interactions and as a probable source of disease resistance. [Copyright &y& Elsevier]

Abstract: Genetic improvement is one of the most effective strategies to prevent rice from blast and bacterial blight (BB) diseases, the two most prevalent diseases jeopardizing rice production. Rice hybrids with dural resistance to blast and BB are needed for sustainable production of food. An incomplete diallele design resulted in 25 crosses between five blast and five BB resistant germplasm accessions. Only one pair of parents, DH146 × TM487, showed polymorphism for all the markers to identify one blast resistance gene Pi25 and three BB resistance genes, Xa21, xa13 and xa5, thus it was used in the marker-assisted selection (MAS). F2 individuals of DH146 × TM487 were genotyped using flanking markers of RM3330 and sequence tagged site (STS) marker SA7 for Pi25. The resistant F2 plants with Pi25 were used for pyramiding BB resistance genes Xa21, xa13 and xa5 identified by the markers pTA248, RM264 and RM153, respectively in subsequent generations. Finally, after selection for agronomic traits and restoration ability among 12 pyramided lines, we acquired an elite restorer line, R8012 including all four target genes (Pi25+Xa21+xa13+xa5). Hybrid Zhong 9A/R8012 derived from the selected line showed stronger resistance to blast and BB, and higher grain yield than the commercial checks uniformally in experimental plots, 2007 state-wide yield trial and 2008 nation-wide yield trial. This study provides a paradigmatic example to show that MAS is a practically feasible tool in effectively pyramiding multiple resistance genes. The resultant restoring line and its hybrid would play an important role in securing rice production in China. [Copyright &y& Elsevier]

Abstract: To find new genes involved in fungal pathogenicity, a mutant (B11) exhibiting enhanced pathogenicity was isolated from an Agrobacterium-mediated transformed Magnaporthe oryzae mutant library. Southern blotting analysis showed that T-DNA insertion in the B11 genome was a single copy. TAIL-PCR and sequence alignment analyses revealed that a putative gene locus MG01679 was interrupted by the T-DNA fragment. By using the PCR-based method, the DNA and cDNA of the mutant gene MG01679 was cloned and sequenced. The open reading frame of MG01679 includes one intron and two exons, and the coding sequence is 696 bp in length and encodes a 231 amino acid peptide. Protein similarity analysis indicated that the gene belongs to the ThiJ/Pfp I protein family, and the gene was thus designated MgThiJ1. MgThiJ1 showed 57% similarity to FOXG_09029 from Fusarium oxysporum and 54% similarity to FGSG_08979 from F. graminearum in protein sequence. MgThiJ1 gene might act as a negative regulator in vegetative growth and pathogenesis in filamentous fungi, and its specific mechanism needs to be studied further. [Copyright &y& Elsevier]