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15 July 2012, Volume 31 Issue 4
    

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    Preface
  • Mycosystema. 2012, 31(4): 461-464.
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    This monographical issue of Mycosystema includes 22 papers, of which eleven articles are related to fungal species investigation, identification and morphological description, five articles related to physiology and genetic variation, two articles related to infection structure and histology, four articles related to pathogenic gene clone and functional gene analysis. The author presented a brief heuristic summary.
  • Papers
  • Mycosystema. 2012, 31(4): 465-470.
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    A new species of Rugonectria, R. sinica, is described based on collections from tropical and subtropical regions of China. Comparisons were made between the new species and a morphologically similar species R. castaneicola. Sequence analysis of the combined ITS and b-tubulin gene of related fungi was also carried out. Both morphological and molecular data support the separation of the Chinese fungus from the Japanese one.
  • Mycosystema. 2012, 31(4): 471-475.
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    A new Lophodermium species, L. saccharicola on Saccharum arundinaceum is described in English and Chinese with an illustration and discussion. Specimens are deposited in the Reference Collection of Forest Fungi of Anhui Agricultural University, Hefei (AAUF).
  • Mycosystema. 2012, 31(4): 476-479.
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    One new species, Pseudocercospora argyreiigena Y.L. Guo on Argyreia sequinii and one new record for China, Pseudocercospora borreriae (Ellis & Everh.) Deighton on Borreria stricta are reported. Descriptions, illustrations, discussions and Latin diagnosis of the new species are provided. Examined specimens are deposited in HMAS.
  • Mycosystema. 2012, 31(4): 480-485.
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    Six rust species collected from southwestern China are reported. Uredo ligulariae-lamarum on Ligularia lamarum are described as new species. Kuehneola peregrina on Clerodendrum yunnanense, Maravalia pterocarpi on Dalbergia yunnanensis, Massee?lla capparidis on Flueggea virosa, Puccinia engleriana on Tabernaemontana divaricata, and Uromyces acetosae on Rumex acetosa are recorded as new to China. All the specimens studied have been deposited in Herbarium Mycologicum Academiae Sinicae (HMAS) in Beijing.
  • Mycosystema. 2012, 31(4): 486-492.
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    About 300 specimens of poroid wood-decaying fungi were collected from Laojun Mountains, Yunnan Province, and 96 polypores were identified from these materials. A checklist of the polypores is given. Substrates and collecting data of each species are provided. Among these species, Phellinus piceicola is described as new. It is characterized by its effused-reflexed to pileate basidiocarps growing on Picea with smaller pores (6–8 per mm) and basidiospores being 3.2–4×2.7–3μm. An illustrated description of the new species is given.
  • Mycosystema. 2012, 31(4): 493-509.
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    The paper deals with the pathogenic wood-decaying fungi on woody plants in China. One hundred and fifty-two species have been recorded, of which 49 species (accounting for 34% of the total pathogenic species) are firstly reported as pathogenic fungi in China. Their host, type of rot, occurrence and distribution were given according to field inventories. Among these fungi, 135 species (accounting for 89%) cause a white rot, while 17 species resulted in a brown rot. Among these fungi 67, 33 and 52 species belong to common, occasional and rare species respectively.
  • Mycosystema. 2012, 31(4): 510-522.
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    Melampsora larici-populina (abbr. MLP) is a heteroecious fungal pathogen causing foliar rust on Populus and Larix species. The genetic diversity of 36 isolates of MLP, collected from 19 locations of eight provinces in China in different years, was investigated by simple sequence repeat (SSR) analysis. A total of 62 alleles for five SSR loci were detected from 91 samples within 36 isolates of MLP, and the effective number of alleles (Ne) ranged from 5.42 to 9.82, with an average of 7.05. The polymorphism information content (PIC) for five loci ranged from 0.64 to 0.89, with an average of 0.79. The average values of observed heterozygosity (Ho) and expected heterozygosity (He) were 0.36 and 0.86, respectively, and Shannon’s information index (I) varied from 1.88 to 2.52, with an average of 2.12. These results showed that all the test MLP isolates were very rich in genetic diversity. The coefficient of gene differentiation among isolate populations (Fst) varied from 0.22 to 0.39, with an average of 0.344, and the average value of gene flow (Nm) was 0.48, which revealed that the genetic diversity appeared mainly within isolate populations (65.60%), specially between isolate populations of MLP from natural forest areas, but also showed distinct differentiation of genetics among isolate populations (34.40%). At geographical population level, the average I and Nei’s gene diversity (Nei’s) were 1.02 and 0.56, respectively, and average values of polymorphic loci (Np) and percentage of polymorphic loci (PPL) were 4.54 and 90.77%, respectively, implying that the genetic diversity among geographical populations was relatively lower than that within isolate populations of MLP. Based on Nei’s genetic distance, ranging from 0.24 to 2.99, 13 geographical populations of MLP isolates from different regions in China could be initially grouped into four clusters: cluster I included isolates By, Th, HD and Sb, cluster II included isolates Cj, HZ, Gl and Qh, cluster III included isolates Nm, Wh and Yl, and cluster Ⅳcomprised Ts and Tt.
  • Mycosystema. 2012, 31(4): 523-530.
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    A new serious disease was found on pomegranate in Panxi Region of Sichuan Province in 2009, and it has become a severe threat to pomegranate production due to its increasing infection in recent years. Disease symptom observation, pathogen isolation and culture, morphological observation, rDNA-ITS phylogenetic analysis, and pathogenicity test were conducted, and the pathogenic fungus was finally identified as Ceratocystis fimbriata. This disease has been found in India and Mengzi of Yunnan Province. It is the first report in Sichuan Province.
  • Mycosystema. 2012, 31(4): 531-539.
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    Tobacco black root rot caused by Thielaviopsis basicola was frequently reported in China in recent years. In this study, a total of 45 isolates of wild types and 11 isolates of white aberrant phenotypes of the pathogen were collected from some provinces of China. According to Punja & Sun’s grouping standards, their grouping identification was conducted. The results showed that six general morphological groups could be distinguished among the isolates, in which groupsⅠ,Ⅱ and Ⅲ were wild types, groups Ⅳ andⅤ aberrant phenotypes. The characteristics of colony and chlamydospores of another aberrant phenotype HLL-1¢ was completely different from those of the five groups mentioned above, therefore it was assigned to the new group, group Ⅵ. The isolating ratios of groups Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ and Ⅵ were 42.9%, 33.9%, 3.6%, 16.0%, 1.8% and 1.8% respectively. Group Ⅰwas mainly distributed in Chongqing and Yunnan, group Ⅲ and Ⅴ in Guizhou, group Ⅳ mainly in Chongqing, Henan and Yunnan, group Ⅵ only in Henan, and group Ⅱ was distributed in all investigating provinces. The rDNA-ITS sequence analysis suggested that the white aberrant phenotypes were identical to their wild types in sequences, but completely different from the isolates growing on other host plants.
  • Mycosystema. 2012, 31(4): 540-547.
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    A total of 198 Rhizoctonia solani isolates were obtained from diseased cotton and soil samples in northern China (Shandong, Hebei and Henan provinces). Anastomosis group (AG) assay and 5.8S rDNA-internal transcribed spacer (ITS) sequence analysis showed the presence of multinucleate Rhizoctonia AG4-HG-I, AG4-HG-III and binucleate Rhizoctonia AG-A, AG-F and AG-Fb groups. The group AG4-HG-I was the dominant(86.86% of total isolates), followed by AG4-HG-III (10.10%), while the AG-A, AG-F, AG-Fb groups were represented by single isolate respectively. The Rhizoctonia AG-A, AG-F, AG-Fb groups were firstly reported from diseased cotton plants, and their pathogenicity to cotton needs further investigation. The 5.8S rDNA-ITS sequence analysis showed that the isolates could be distinctly separated based on their AG types. The isolates of the same AG (or sub-AG) showed high sequence identity. The nuclear phase observation showed that the numbers of nuclei were significantly different between the two subgroups of AG-4.
  • Mycosystema. 2012, 31(4): 548-559.
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    The infection process of Marssonina coronaria was investigated on leaves of susceptible and resistant apple cultivars by means of light and electron microscopy. Infection and colonization by the pathogen could be divided into six stages: spore germination and germ tube formation, appressorium formation, penetration, haustorium formation in mesophyll cells, expansion of mycelium between and in mesophyll cells, and acervulus formation. Cell wall swelling and degradation, plasmolysis, accumulation of starch grains and osmiphilic globules, disruption of grana lamellae and vacuolization of mitochondrion were observed during mycelial expansion in host tissues. Branching rate of germ tubes, formation rate of appressoria and expansion of mycelium were significantly different between susceptible and resistant cultivars; however, the conidial germination rate did not show significant differences. For resistant cultivar, the pathogen’s penetration and formation of subcuticular hyphae, haustoria in mesophyll cells, and acervuli were clearly delayed, and the number of germ tube branches and haustoria in the mesophyll cells were all decreased. Hypha grew more slowly and deposited more electron-dense material in the leaves of resistant cultivars. It is concluded that the resistance of apple cultivars against Marssonina coronaria is related to inhibition of fungal infection, colonization, and mycelial expansion processes in host tissues.
  • Mycosystema. 2012, 31(4): 560-566.
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    The ontogeny of teliospore of Puccinia striiformis f. sp. tritici (Pst), the causal agent of wheat stripe rust, was performed and observed by cryo-sectioning technique associated with light and electron microscopies. The observation showed that Pst teliospores derivated from binucleate sporogenous cells lining the base of telia. At the early stage, a spore-bud outgrew from one end of sporogenous cells and expanded to form septum and related structures such as teliospore initial, pedicel and primary teliospore cell resulted from bud division. The primary teliospore cell developed to be a two-celled teliospore with two nuclei in each cell after completion of the primary teliospore nuclear division and subsequent development of a septum. The matured teliospores were characterized by smooth surface, thickened cell wall, nuclear fusion, cytoplasmic condensing and accumulation of lipid droplets and glycogen-like substances. A lotus-shaped peridium structure around some telia was observed in some telia of Pst during telial formation.
  • Mycosystema. 2012, 31(4): 567-573.
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    Two isolates of Ustilaginoidea virens with natural marker, ZJa0201 and SXa0101, were obtained from albinotic false smut balls of rice. The albinotic isolates grew rapidly and reached about 3 times the growth speed of wild isolates in potato sucrose agar (PSA) medium, and no chlamydospore was detected. Sporulation of the albinotic isolates decreased significantly in PSA medium. The analysis of rDNA-ITS sequences showed that they shared 99.6% similarity to the known wild isolates of U. virens, and their rDNA-IGS sequences belonged to the most common type, consisted of 2 repetitive units of 77bp in the central various region. It is suggested that these albinotic isolates were the mutants of sporulating degeneration of Ustilaginoidea virens. The albinotic isolates could produce immature sclerotia in 30 days in PSA and UV irradiation could promote the formation of selerotia. The immature sclerotia could not germinate.
  • Mycosystema. 2012, 31(4): 574-583.
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    The paper deals with the effect of different carbon and nitrogen sources, pH and temperature on mycelium growth, mycelium dry weight and spore germination rate of Fusarium sulphureum, the causal agent of potato dry rot. The results showed that the optimum carbon and nitrogen sources for the pathogen mycelium growth on solid media were glucose and maltose, and peptone respectively with the most suitable pH 8.0. Maltose and NaNO3 were the optimum carbon and nitrogen resources for its mycelium growth in liquid media with the most suitable pH 6.0. The optimum carbon and nitrogen resources for spore germination were sodium carboxymethyl cellulose (CMC), peptone and glutamic acid (Glu) with the optimum pH 6.0–8.0. The optimum temperature was 25℃ for the pathogen growth on solid media or in liquid media. The lethal temperature for the conidia was 50℃ for 10 minutes.
  • Mycosystema. 2012, 31(4): 584-592.
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    Fusarium oxysporum f. sp. cubense race 4 (Focr4) is considered as one of the most destructive pathogens of the world distributed soil-borne banana. Its pathogenesis has not been clearly understood. The pathogenicity of mutant Focr4-1562 was significantly weakened after T-DNA insertion in its gene sequence. The inserted exogenous gene caused changes in functions of some genes in the △Focr4-1562. By means of cellophane penetration test as well as pathogenic test by inoculating live leaves and roots, changes in pathogenic phenotype of the mutant Focr4-1562 and △Focr4-1562 were compared with the wild type Focr4. The mutant Focr4-1562 and △Focr4-1562 could not grow through cellophane, and didn’t cause any disease spots and brown coloration in corm vascular bundle. The results showed that the optimum growth temperature of the wild type Focr4, Focr4-1562 and △Focr4-1562 were all at 28℃, and their optimum growth pH was 7.0 to 8.0. No evident difference was found in their spore morphology, but the sporulation of △Focr4-1562 was obviously delayed, and its sporulation capacity was significantly decreased. The Focr4-1562 and △Focr4-1562 were more resistant to cell wall degrading enzyme than the wild type Focr4-193-6. It is concluded that the knockout of the pathogenic gene is responsible for conidial production and cell wall formation of the wild type Focr4-193-6.
  • Mycosystema. 2012, 31(4): 593-607.
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    Fusarium wilt of banana (Musa spp.), caused by Fusarium oxysporum f. sp. cubense race 1, is the most important factor limiting the plantation of plantain banana (AAB Group Fenjao) on the large scale. The pathogenic mechanism is still not very clear yet. A nonpathogenic mutant Focr1-328 with a T-DNA insertion was recently obtained. The inactivated gene resulting from a T-DNA insertion was located in the genomic sequences of Focr1. Subsequently, the gene was knocked out and a deletion mutant △Focr1-328 was obtained by homologous recombination. In order to investigate the function of the pathogenic related gene, the pathogenicity of the wild type Focr1-N2 and the deletion mutant △Focr1-328 was tested by inoculating living leaves and roots with spore suspension. The differences in the colony morphology, mycelial growth and conidial production on PDA, the growth rates and morphology on different carbon and nitrogen sources and the biomass, potential of hydrogen value, optical density value as well as cellophane penetrating capability were studied. The results of pathogenicity experiments showed that the deletion mutant △Focr1-328 was nonpathogenic, indicating that △Focr1-328 lost the pathogenic capability. The growth rate, the quantity and germination rate of conidia and the biomass of mycelia of the deletion mutant △Focr1-328 were significantly lower than those of wild type. The best carbon sources for the mutant and the wild type growth was sorbitol and maltose, respectively. The optimum Nitrogen source was sodium nitrate in both cases but the growth rates and colors of mutant and wild type were different on various C and N media. The wild strain penetrated cellophane readily, but the mutant could not. The results indicated that pathogenic related gene which was inactivated by T-DNA insertion is related to the utilization of C source, acid production and mycelial penetration capability.
  • Mycosystema. 2012, 31(4): 608-622.
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    Thirty-nine single pustule isolates were collected from volunteer wheat seedlings in Tianshui, Longnan and Dingxi, southern Gansu Province, for exploring the virulent component and population structure of Puccinia striiformis f. sp. tritici on volunteers by virulence analysis using both Chinese and U.S. differentials and TP-M13-SSR fluorescent labeling methods. From the isolates, 9 races were identified based on reactions on the 19 Chinese differentials and 24 races on the 20 U.S. ones. A total of 30 virulence patterns were identified among the 39 isolates based on their reactions on both Chinese and U.S. differentials. Based on Chinese differentials, CYR32 and CYR33 were the dominant races, the virulence frequencies were 35.9% and 30.8%, respectively. The 39 isolates were clustered into 6 groups by both the virulence and the SSR data, which were switched to the middle value of the similarity range data. Virulence and SSR data had a low (r=0.043) correlation. There were same phenotypes or genotypes (similarity 100%) from different geographical populations by both virulence and SSR analyses, and the gene flow value (Nm) was 2.59. The results above reveal that there exists abundant virulence phenotype and molecular genotype diversity of Pst on Longnan volunteer wheat, and there is frequent gene flow in different populations, which are reserved high diversity source pathogens for autumn seedlings in Longnan over-summering zone. The results of present study can provide a theoretical basis for integrated management of wheat stripe rust and effective deployment of resistance genes in Pst over-summering zones.
  • Mycosystema. 2012, 31(4): 623-629.
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    Laccases are copper-containing phenol oxidases which are involved in plant pathogenesis, pigment synthesis, and delignification. In order to understand the catalysis and catalytic activity in Cochliobolus lunatus, the intracellular laccase activity of the fungus was tested by spectrophotometer under 420nm with 2,2’-azobis (3-thylbenzothiazole-6-sulfonaic acid) (ABTS) as the substrate and the absorbance results suggest that the optimal reaction conditions were pH 2.8, 500μmol/L Cu2+ and 0.6μmol/L substrate concentration. The homologous fragments of ClLac1 gene was cloned by PCR amplification with degenerated primer sets designed around the copper-binding-sites. Its full length cDNA sequence was obtained by RACE method with 1,803bp encoding 600 amino acids and the deduced protein amino acids were highly identitical with the laccases of other fungi. It contained four conserved copper-binding sites, eight putative N-glycosylation sites and a signal peptide sequence was found in the N-terminal by bioinformatics analysis. The promoter region contained one MRE (metal responsive element), one STRE (stress responsive element), two CreA-binding sites, four nitrogen factor binding sites.
  • Mycosystema. 2012, 31(4): 630-638.
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    The diseased stems, leaves and faceplates of sunflower with black stem symptom were sampled in Xinjiang Autonomous Region, China. Twenty fungal isolates were finally isolated from the materials. Isolates XJ011 and XJ111 were found to be pathogenic to sunflower plants. ITS sequence analysis indicated the isolates XJ011 and XJ111 were Phoma macdonaldii. A pair of specific primers 320FOR/320REV were designed for rDNA-ITS of P. macdonaldii according to polymorphism region, and it can be used to detect P. macdonaldii specifically with highly sensitivity of 1fg concentration.
  • short communications
  • Mycosystema. 2012, 31(4): 639-641.
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    Three new records of Phyllachora from China are reported. They are Phyllachora centothecae on Centotheca lappacea, Phyllachora coorgiana on Coix lachryma-jobi, and Phyllachora digitariicola on Digitaria sanguinalis. Specimens studied were collected from Jiangxi, Anhui, Hainan, Shaanxi and Yunnan provinces. Descriptions and illustrations of the species are given based on Chinese specimens. The specimens are deposited in Mycological Herbarium of the Northwest Agriculture & Forestry University (HMUABO) and Mycological Herbarium of the Yunnan Agricultural University (MHYAU), China.
  • Mycosystema. 2012, 31(4): 645-647.
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    Canna indica is a well-known ornamental plant. The pathogen of black leaf spot disease in Kunming, China was found to be a very widespread Alternaria species, Alternaria alternata. The pathogenicity of the fungus was investigated.
  • Mycosystema. 2012, 31(4): 782-784.
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    Three new Chinese records of Phyllachora are reported. They are Phyllachora minutissima on Pennisetum flaccidum, P. platyelliptica on Themeda giguntia var. caudata, and P. contigua on Millettia sp. Descriptions and illustrations are given based on Chinese specimens. The specimens are deposited in Mycological Herbarium of the Yunnan Agricultural University (MHYAU), China.