[Show abstract][Hide abstract]ABSTRACT: Twenty-nine isolates of Thanatephorus cucumeris (Rhizoctonia solani) AG-2-2 IV were collected from the roots, petioles, and leaves of diseased sugar beets in Hokkaido, Japan. We examined the genetic variation of the field isolates using somatic compatibility grouping of progeny (cultured isolates derived from induced basidiospores) based on analysis of hyphal anastomosis reactions (i.e., hyphal perfect fusion) and inter-simple sequence repeats (ISSRs). The number of somatic compatibility groups (SCGs) of single basidiospore isolates was strongly correlated with the host plant tissue from which the parental isolates were obtained. Parental isolates from roots and petioles tended to be genetically heterogeneous and generated plural SCGs, whereas isolates (except for two non-self-anastomosing isolates) from leaves tended to be homogeneous and generated a single SCG. Heterogeneous sibling basidiospore isolates yielded homogeneous progeny within a few generations. These findings were supported by the results of ISSR analysis, which showed that the homogeneous isolates generated progeny with the same genotype, whereas heterogeneous isolates generated progeny with different genotypes. However, like SCGs, ISSR genotypes of heterogeneous progeny tended to be homogeneous within two or three generations. Additionally, we examined clonal diversity during the basidiospore infection process over a 2-year period. A heterogeneous isolate generated a large number of progeny SCGs, thereby increasing clonal diversity. In contrast, progeny SCGs were almost all the same in a homogeneous isolate plot with a few exceptions. These results indicate that infection of T. cucumeris basidiospores play a role in the clonal diversity of AG-2-2 IV isolates, as indicated by progeny SCGs in the field.
Full-text · Article · Mar 2014 · Journal of General Plant Pathology
[Show abstract][Hide abstract]ABSTRACT: AG-A belongs to the binucleate Rhizoctonia (BNR) anastomosis group (AG) of the Ceratobasidium teleomorph, which parasitizes the roots of many plant species. Ninety nine isolate species of AG-A were obtained from Tibet,
Sichuan, and Yunnan Province in China. All isolates were divided into three types based on their cultural characteristics.
Type I: abundant aerial mycelia, dense hyphae, loose sclerotia; Type II: abundant aerial mycelia, no sclerotia. Type III:
sparse aerial mycelium and no sclerotia. All of the isolates infected the seedlings of Chinese mustard and Chinese cabbage,
causing the formation of lesions on the stem and a brown discoloration of the roots. Sequence analysis of the 5.8S rDNA-ITS
showed a similarity of 98–100% among the isolates. Inter Simple Sequence Repeat (ISSR) was used to detect genetic variation
in binucleate Rhizoctonia spp. Forty two AG-A isolates were amplified using 15 random primers. From a total of 164 bands, 144 bands (87.8%) were polymorphic
in the 42 tested isolates. A dendrogram showing genetic relationships between the isolates was constructed using unweighted
pair-group averages based on genetic distances. According to the dendrogram, the 42 tested isolates could be aligned into
three clusters with a genetic similarity coefficient of 0.29, the first clusters including 27 isolates with III of culture
characteristics on PDA; the second clusters included eight isolates with I of cultural characteristics on PDA; the third cluster
included seven isolates with II of cultural characteristics on PDA. The results of ISSR analysis showed an association between
the hosts of these isolates. Our results showed that ISSR analysis can reveal more molecular variation among isolates of AG-A
than sequence analysis using the 5.8S rDNA-ITS.
[Show abstract][Hide abstract]ABSTRACT: Random amplified polymorphic DNA (RAPD) analysis using the OPG-06 primer generated specific patterns for Japanese genotypes
US-1, JP-1, and a new A1 (JP-2, JP-3, and JP-4) of Phytophthora infestans. N605, a specific RAPD fragment, was cloned and sequenced. PCR primers BD1/BD2 were constructed based on the N605 sequence
and were used to clarify the genotypes. PCR products using the BD1/BD2 primers (N605ab marker) easily distinguished the new
A1 from US-1 and JP-1. This technique provides a simple and effective method for rapid genotype discrimination that can be
used in ecological experiments and forecasts for the occurrence of late blight.
No preview · Article · Apr 2008 · Journal of General Plant Pathology
[Show abstract][Hide abstract]ABSTRACT: Five Pythium species (Pythium irregulare, P. mamillatum, P. myriotylum, P. spinosum and P. ultimum var. ultimum) were isolated from the hypocotyls and roots of kidney bean plants with damping-off from a commercial field and from experimental
plots that have undergone either continuous cropping with kidney bean or rotational cropping with arable crops. In inoculation
tests, all five Pythium species were pathogenic to kidney bean. This is the first report of damping-off of kidney bean caused by Pythium species; we named this disease damping-off of kidney bean.
No preview · Article · Feb 2008 · Journal of General Plant Pathology
[Show abstract][Hide abstract]ABSTRACT: Twelve isolates of Japanese Phytophthora infestans, which differed from the major genotypes US-1, JP-1, JP-2, and JP-3, were analyzed for RG57 fingerprints, mtDNA haplotypes,
two allozyme genotypes, and mating types. Genotypes JP-1.1, JP-2.1, JP-2.2, JP-3.1, and JP-4 were newly defined. JP-1.1 and
JP-2.1 were isolated discontinuously from potato fields in several years, and JP-1.1 was found in Hokkaido and Kagoshima.
These results show that some minor genotypes can overwinter and disperse from their original site.
No preview · Article · Sep 2007 · Journal of General Plant Pathology
[Show abstract][Hide abstract]ABSTRACT: Phialophora gregata f. sp. adzukicola, a causal agent of brown stem rot in adzuki beans, produces phytotoxic compounds: gregatins A, B, C, D, and E. Gregatins
A, C, and D cause wilting and vascular browning in adzuki beans, which resemble the disease symptoms. Thus, gregatins are
considered to be involved in pathogenicity. However, molecular analyses have not been conducted, and little is known about
other pathogenic factors. We sought to isolate nonpathogenic and gregatin-deficient mutants through Agrobacterium tumefaciens-mediated transformation (ATMT) for cloning of pathogenicity-related genes. The co-cultivation of P. gregata and A. tumefaciens for 48h at 20°C with 200μM acetosyringone resulted in approximately 80 transformants per 106 conidia. The presence of acetosyringone in the A. tumefaciens pre-cultivation period led to an increase in T-DNA copy number per genome. Of 420 and 110 transformants tested for their
pathogenicity and productivity of gregatins, one nonpathogenic and three gregatin-deficient mutants were obtained, respectively.
The nonpathogenic mutant produced gregatins, whereas the gregatin-deficient mutants had pathogenicity comparable to the wild-type
strain. This is the first report of ATMT of P. gregata. Further analysis of these mutants will help reveal the nature of the pathogenicity of this fungus including the role of
gregatin in pathogenesis.
No preview · Article · Jul 2007 · Journal of General Plant Pathology
[Show abstract][Hide abstract]ABSTRACT: During July 2004, wirestem was frequently observed on the seedlings of Betula nigra at Dehong district in Yunnan Province, China. Isolates of Rhizoctonia spp. consistently obtained from their diseased leaves, roots and stems were identified as belonging to binucleate Rhizoctonia anastomosis groups (AG) AG-P and AG-R, and R. solani AG-I IB and AG-4 HG-I, based on cultural characteristics, nuclear staining, anastomisis reaction and analysis of their ITS rDNA region. The percentage of recovery of AG-P, AG-1, AG-R and AG-4 was 48%, 39%, 8% and 3%, respectively. This is the first report of wirestem of red birch cause by binucleate Rhizoctonia AG-P and AG-R, and R. solani AG-1 IB and AG-4 HG-I in China.
No preview · Article · Jan 2006 · Journal of Phytopathology
[Show abstract][Hide abstract]ABSTRACT: A total of 401 isolates of Phytophthora infestans were collected from eight Asian regions (Korea, India, Taiwan, Indonesia, Thailand, Nepal, China and Japan) between 1992 and 2000 – 318 from potato and 83 from tomato. The isolates were analysed for mating type, metalaxyl resistance, RG57 fingerprinting, mitochondrial DNA (mtDNA) haplotype and the polymorphism of three allozyme loci, i.e. glucose-6-phosphate isomerase (Gpi), peptidase (Pep) and malic enzyme (Me). The isolates were multilocus-genotyped based on RFLP (RG57) fingerprint, dilocus allozyme genotype, mtDNA haplotype and mating type. Twenty multilocus genotypes were identified among 125 isolates. Of these genotypes, 14 had not been previously reported. Some of the multilocus genotypes were common to isolates from several geographical regions, suggesting migration. The metalaxyl-resistant isolates belonged to the multilocus genotypes JP-1, JP-2, and JP-3. Multilocus genotypes coexisting in a single field were found in following regions: Thailand (1994), central China (1996), Nepal (1997) and Japan (1998 and 2000). The possible origins of certain genotypes are discussed, including the possibility of sexual recombination within the P. infestans populations in Nepal and perhaps Thailand.
[Show abstract][Hide abstract]ABSTRACT: Adzuki bean cultivar Acc259, which is resistant to races 1 and 2 of Phialophora gregata f. sp. adzukicola, was used as a breeding resource for resistance to brown stem rot (BSR). During the third year after two successive cultivations of Acc259, a severe outbreak of BSR occurred in an experimental plot at the Tokachi Agricultural Experiment Station, Hokkaido, Japan. The isolates obtained from diseased plants were virulent to Erimo-shozu (susceptible to all races) and Acc259 but avirulent to Kita-no-otome (resistant to race 1 but susceptible to race 2). The existence of a new race of P. gregata f. sp. adzukicola, designated race 3, was determined; and its frequency in the plot soil was shown to increase from 16.7% before planting Acc259 to 100% after the third year. Of 140 isolates from the commercial production area that were formerly identified as race 1, 13 were actually race 3 and were restricted to certain limited fields.
No preview · Article · Sep 2005 · Journal of General Plant Pathology
[Show abstract][Hide abstract]ABSTRACT: Twenty binucleate Rhizoctonia (BNR) isolates were collected from roots of soya bean, pea, snap bean and pak choy with root rot symptoms in Yunnan Province, China. Chinese isolates anastomosed with the tester isolate of anastomosis group-A (AG-A; C-517) with a high C2 fusion rate (>70%). Chinese isolates were pathogenic to soya bean, pea, snap bean and pak choy and had 97% similarity sequence of 5.8S rDNA-internal transcribed spacer with AG-A tester isolates SN-2 and C-662. When compared with other groups, AG-Ba and AG-Bb, Chinese isolates showed 77% sequence similarity. These results show that Chinese isolates belong to AG-A of BNR. Growth rate, hyphal diameter, cultural characteristics and pathogenicity of the Chinese isolates differed significantly from the tester isolate of AG-A. This is the first report on AG-A in China.
No preview · Article · Jun 2005 · Journal of Phytopathology
[Show abstract][Hide abstract]ABSTRACT: During December 2003, stem canker and wirestem were observed on the stems of green amaranth (Amaranthus viridis) and Chinese amaranth (Amaranthus tricolor) in greenhouses at Ximao district in Yunnnan Province, China. Isolates of Rhizoctonia solani obtained from the two amaranths with stem canker and wirestem, were identical to anastomosis group (AG)-4. The isolates from diseased plant showed high virulence on young seedlings of two amaranths. Results of sequence analysis of 5.8s rDNA-ITS of Chinese isolates showed 99–100% sequence similarity with AG-4HG-III tester isolates. When compared with other subgroups of AG-4, Chinese isolates showed similarity levels of 94%. This is the first report of stem canker and wirestem of Green amaranth and Chinese amaranth caused by AG-4HG-III and AG-4HG-III in China.
No preview · Article · Mar 2005 · Journal of Phytopathology
[Show abstract][Hide abstract]ABSTRACT: Abstract Since 1997, severe epidemics of a black rot disease of maize (Zea mays) have occurred at Yuanmou County, Yunnan Province, China. Olpitrichum tenellum, identified by morphology of conidia and conidiophores was recovered from infected plant material. Its strong infectivity on maize and causal role in inducing black rot was confirmed by pathogenicity tests in the greenhouse. This is the first report of black rot of maize caused by O. tenellum in China.
No preview · Article · Feb 2005 · Journal of Phytopathology
[Show abstract][Hide abstract]ABSTRACT: The sexual preferences of Japanese isolates of Phytophthora infestans were determined by mating on agar, in broth, or in plants. The influence of their sexual preference was confirmed in the host tissues. Three wild-type isolates and a -glucuronidase (GUS) transformant were co-cultured to identify the origin of antheridia and oogonia. Japanese A1 isolate had a unique sexual preference compared with foreign isolates. It produced self-fertile oospores with about 40% of total gametangia but tended to form antheridia on V-8 agar medium. In addition, oospores were formed in plants, but their sexual preference could not be reflected in vitro.
No preview · Article · Jan 2005 · Journal of General Plant Pathology
[Show abstract][Hide abstract]ABSTRACT: The genetic characteristics of the dominant genotypes of Phytophthora infestans in Japan (US-1, JP-1, Japanese A1-A, A1-B) were compared. Differences were evident in the peptidase genotype, amplified fragment length polymorphism, and RG57 DNA fingerprints. Almost all of the fingerprint bands for the Japanese genotype A1-B were also present in JP-1 and Japanese A1-A, and few bands were unique to Japanese A1-B. These results suggest that the Japanese A1-B genotype was generated from sexual reproduction involving Japanese A1-A and JP-1 or related genotypes.
No preview · Article · Jan 2005 · Journal of General Plant Pathology
[Show abstract][Hide abstract]ABSTRACT: The mating type, glucose-6-phosphate isomerase (Gpi) and peptidase (Pep) genotypes, RG57 fingerprint, and mitochondrial DNA (mtDNA) haplotype of Chinese isolates of Phytophthora infestans collected in Hebei and Gansu in 1996 were compared with those of Japanese isolates collected during 1997–2000. The Chinese isolates were divided into four genotypes, one of which was identical to the dominant Japanese genotype, A1-A (mating type A1; Gpi 100/100; Pep 100/100; RG57 100010001100110100011001110: 1–25, 14a, and 24a; and mtDNA haplotype IIa). Comparison of the genotypes with reported data revealed that some completely and partially identical genotypes occur in Russia and parts of Europe. The other two A1 genotypes and one A2 genotype were also detected in Gansu (Gpi 100/100, Pep 100/100, and mtDNA haplotype Ia), which were regarded as unique to this region.
No preview · Article · Jul 2004 · Journal of General Plant Pathology