The first occurrence of leaf mold of tomato caused by races 4.9 and 4.9.11 of <Emphasis Type="Italic">Passalora fulva</Emphasis> (syn. <Emphasis Type="Italic">Fulvia fulva</Emphasis>) in Japan

Tomato leaf mold caused by Passalora fulva was found on two tomato varieties carrying the Cf-9 gene in Japan, in 2007. The isolates obtained from Chiba and Fukushima were identified as race 4.9.11, and those from Gunma were races 4.9 or 4.9.11. This is the first report in Japan of tomato leaf mold caused by P. fulva strains that can overcome the Cf-9 gene.     

First report of blueberry red ringspot disease caused by <Emphasis Type="Italic">Blueberry</Emphasis><Emphasis Type="Italic">red</Emphasis><Emphasis Type="Italic">ringspot</Emphasis><Emphasis Type="Italic">virus</Emphasis> in Japan

Virus-like symptoms—red ringspots on stems and leaves, circular blotches or pale spots on fruit—were found on commercial highbush blueberry (Vaccinium corymbosum) cultivars Blueray, Weymouth, Duke and Sierra in Japan. In PCR testing, single DNA fragments were amplified from total nucleic acid samples of the diseased blueberry bushes using primers specific to Blueberry red ringspot virus (BRRV). Sequencing analysis of the amplified products revealed 95.7–97.7% nucleotide sequence identity with the BRRV genome. This paper is the first report of blueberry red ringspot disease caused by BRRV in Japan. The nucleotide sequence data reported in this paper are available in the GenBank/EMBL/DDBJ database as accessions AB469884 to AB469893 for BRRV isolates from Japan.     

Discrimination of <Emphasis Type="Italic">Xanthomonas campestris</Emphasis> pv. <Emphasis Type="Italic">campestris</Emphasis> races among strains from northwestern Spain by <Emphasis Type="Italic">Brassica</Emphasis> spp. genotypes and rep-PCR

Black rot, caused by Xanthomonas campestris pv. campestris (Xcc) is a severe seedborne disease of Brassica crops around the world. Nine races are recognized, being races 1 and 4 the most aggressive and widespread. The identification of Xcc races affecting Brassica crops in a target area is necessary to establish adequate control measures and breeding strategies. The objectives of this study were to isolate and identify Xcc strains from northwestern Spain by using semi-selective medium and pathogenicity tests, determine the existing races of Xcc in this area by differential series of Brassica spp., and evaluate the use of repetitive DNA polymerase chain reaction-based fingerprinting (rep-PCR) to differentiate among the nine existing Xcc races. Seventy five isolates recovered from infected fields were identified as Xcc. Race-typing tests determined the presence of the following seven pathogen races: 1, 4, 5, 6, 7, 8 and 9. Race 4 was the most frequent in Brassica oleracea and race 6 in Brassica rapa crops, therefore breeding should be focussed in obtaining resistant varieties to both races. Cluster analysis derived from the combined fingerprints showed four groups, but no clear relationship to race, crop or geographical origin was found. Rep-PCR analysis was found not to be a reliable method to discriminate among Xcc races, therefore race typing of Xcc isolates should be done by using the differential series of Brassica spp. genotypes or another alternative approach.     

Anthracnose of salt-wort (<Emphasis Type="Italic">Salsola komarovii</Emphasis>) caused by <Emphasis Type="Italic">Colletotrichum truncatum</Emphasis>

In July 2006, black rot was observed on the leaves of 4-leaf-stage seedlings of salt-wort (Salsola komarovii) in Yamagata Prefecture, Japan. We isolated two single-conidial isolates from the diseased leaves. Although colony appearance of the isolates was different from that of each other, both isolates were identified as Colletotrichum truncatum by morphology and molecular similarity. After inoculation of healthy salt-wort plants with the isolates, the isolates were reisolated from symptomatic plants. We thus propose a new disease, anthracnose of salt-wort.     

Multigene phylogenetic analysis of inter- and intraspecific relationships in <Emphasis Type="Italic">Venturia nashicola</Emphasis> and <Emphasis Type="Italic">V. pirina</Emphasis>

Isolates of Venturia species isolated from pear in Japan, China, Taiwan and Israel were used in this study to analyze their molecular phylogenetic relationship. The nucleotides of rDNA-ITS, partial β-tubulin and elongation factor 1α genes were sequenced directly after PCR. Based on these sequence data two phylogenetic groups could be distinguished. Isolates collected from Asian pears such as Japanese and Chinese pears formed a distinct evolutionary lineage from those derived from European and Syrian pears. This result corroborated the early taxonomic separation of V. nashicola from V. pirina. In addition, trees from single-locus data sets and the combined data set showed that all isolates of V. nashicola were included in a monophyletic group and representative isolates of five pathological races originating from different locations and cultivars formed a single lineage. In contrast, two distinct evolutionary lineages were revealed in V. pirina and isolates of five races were scattered in two lineages. Israeli isolates of race 2 as well as two Japanese isolates of V. pirina formed a distinct lineage from other isolates of this species, while other Israeli isolates belonging to races 1, 3, 4, and 5 were closely related to each other and formed another lineage. It was indicated that the evolution of pathological races in V. nashicola might have occurred relatively recently as compared with V. pirina.     

Pathogenicity of morphologically different isolates of <Emphasis Type="Italic">Sclerotinia sclerotiorum</Emphasis> with <Emphasis Type="Italic">Brassica napus</Emphasis> and <Emphasis Type="Italic">B. juncea</Emphasis> genotypes

Sclerotinia stem rot caused by Sclerotinia sclerotiorum is a serious threat to oilseed production in Australia. Eight isolates of S. sclerotiorum were collected from Mount Barker and Walkway regions of Western Australia in 2004. Comparisons of colony characteristics on potato dextrose agar (PDA) as well as pathogenicity studies of these isolates were conducted on selected genotypes of Brassica napus and B. juncea. Three darkly-pigmented isolates (WW-1, WW-2 and WW-4) were identified and this is the first report of the occurrence of such isolates in Australia. There was, however, no correlation between pigmentation or colony diameter on PDA with the pathogenicity of different isolates of this pathogen as measured by diameter of cotyledon lesion on the host genotypes. Significant differences were observed between different isolates (P ≤ 0.001) in two separate experiments in relation to pathogenicity. Differences were also observed between the different Brassica genotypes (P ≤ 0.001) in their responses to different isolates of S. sclerotiorum and there was also a significant host × pathogen interaction (P ≤ 0.001) in both experiments. Responses between the two experiments were significantly correlated in relation to diameter of cotyledon lesions caused by selected isolates (r = 0.79; P < 0.001, n = 48). Responses of some genotypes (e.g., cv. Charlton) were relatively consistent irrespective of the isolates of the pathogen tested, whereas highly variable responses were observed in some other genotypes (e.g., Zhongyou-ang No. 4, Purler) against the same isolates. Results indicate that, ideally, more than one S. sclerotiorum isolate should be included in any screening programme to identify host resistance. Unique genotypes which show relatively consistent resistant reactions (e.g., cv. Charlton) across different isolates are the best for commercial exploitation of this resistance in oilseed Brassica breeding programmes.     

Characterization of <Emphasis Type="Italic">Inago1</Emphasis> and <Emphasis Type="Italic">Inago2</Emphasis> retrotransposons in <Emphasis Type="Italic">Magnaporthe oryzae</Emphasis>

From the genome of a Japanese field isolate of the rice blast fungus, Magnaporthe oryzae, we newly identified Inago1 and Inago2 LTR retrotransposons. Both elements were found to be Ty3/gypsy-like elements whose copies were dispersed within the genome of Magnaporthe spp. isolates infecting rice and other monocot plants. Southern hybridization patterns of nine re-isolates derived from conidia of the strain Ina168 produced after a methyl viologen treatment were not changed, indicating that the insertion pattern of Inago elements is relatively stable.     

Reaction of <Emphasis Type="Italic">Leersia</Emphasis> grasses to <Emphasis Type="Italic">Xanthomonas oryzae</Emphasis> pv. <Emphasis Type="Italic">oryzae</Emphasis> collected from Japan and Asian countries

The present study was conducted to determine if there is specificity in the host-pathogen relationship between the isolates of Xanthomonas oryzae pv. oryzae, the causal bacterium for rice blight and Leersia grasses, the alternative weed hosts of the disease. Plants of three species of Leersia, namely, L. sayanuka, L. oryzoides and L. japonica, were collected from various parts of Japan and were inoculated with the X. oryzae pv. oryzae isolates obtained from various locations in Japan and from 11 Asian countries. Four L. sayanuka plants were found susceptible to all Race II isolates and some Race I isolates, but were resistant to all Race III isolates. Race III is known to have a wider range pathogenicity to rice cultivar groups compared with Race I and II. Although the reactions of two L. oryzoides plants to Race I and II isolates were similar to that of L. sayanuka, the L. oryzoides plant collected from Niigata Prefecture showed a susceptible reaction to some Race III isolates. On the other hand, L. japonica plants gave reactions different those of L. sayanuka and L. oryzoides, with two plants of L. japonica found to be resistant to all test isolates collected from Japan. The Asian isolates exhibited a wide host range against the international differential rice cultivars, but almost all of them were avirulent to Leersia plants. These results indicate that the relationship between the pathogenicity of the causal bacterium and the resistance of host plants is very complex, and suggest that pathogenic diversity of X. oryzae pv. oryzae might be related to the resistance of Leersia spp.     

Population structure of <Emphasis Type="Italic">Eleusine</Emphasis> isolates of <Emphasis Type="Italic">Pyricularia oryzae</Emphasis> and its evolutionary implications

Population structure of Eleusine isolates of Pyricularia oryzae (Magnaporthe oryzae) was examined using DNA markers. On the basis of rDNA sequences, Eleusine isolates were divided into two groups. One group clustered with Triticum isolates, while the other clustered with Eragrostis isolates. This grouping was supported by DNA fingerprinting with three repetitive elements: MGR586, MGR583, and grasshopper. These results suggest that the population of Eleusine isolates is composed of at least two groups that evolved independently from the original population of P. oryzae. Most of the isolates that were collected just after an outbreak of finger millet blast in the 1970s had almost identical fingerprint profiles although they were collected in distant prefectures. This result supports the idea that the outbreak was caused by seed transmission of a particular strain of Eleusine isolates.     

Fusarium rot of hyacinth caused by <Emphasis Type="Italic">Gibberella zeae</Emphasis> (anamorph: <Emphasis Type="Italic">Fusarium</Emphasis><Emphasis Type="Italic"> graminearum</Emphasis>)

Severe rot of leaves, peduncles and flowers caused by Gibberella zeae (anamorph: Fusarium graminearum) was found on potted plants of hyacinth (Hyacinthus orientalis), a liliaceous ornamental, in greenhouses in Kagawa Prefecture, Japan, in January 2001. This disease was named “Fusarium rot of hyacinth” as a new disease because only the anamorph, F. graminearum, was identified on the diseased host plant. The authors contributed equally to this work. The fungal isolate and its nucleotide sequence data obtained in this study were deposited in the Genebank, National Institute of Agrobiological Sciences and the DDBJ/EMBL/GenBank databases under the accession numbers MAFF239499 and AB366161, respectively.     

Characterization of <Emphasis Type="Italic">Phytophthora clandestina</Emphasis> races on <Emphasis Type="Italic">Trifolium subterraneum</Emphasis> in Western Australia

Phytophthora clandestina is a causal agent of root rot disease of subterranean clover in Western Australia (W.A). As a significant number of isolates of P. clandestina from W.A. could not previously be designated using existing differentials, a comprehensive set of subterranean clover (Trifolium subterraneum) cultivars was used as differentials to delineate a broader range of races of the pathogen. One hundred and one isolates of the pathogen collected from W.A. were screened on nine subterranean clover cultivars, of which seven were found to be useful as host differentials. A total of 10 races (in contrast to the five recognized previously) were defined and differentiated using octal nomenclature, presenting a clearer picture of the racial distribution of P. clandestina among W.A. isolates. Differences were found in the race populations between Australian states and are therefore important to the selection/breeding of cultivars for specific regions of Australia to counter the predominant race populations and for enforcing quarantine measures in relation to seed movements within and outside Australia. The octal nomenclature used provides a sound basis for follow-up studies and future race designations. Races 173 and 177 in this study were widely distributed and were the most common races in W.A., and together constitute 80% of the isolates characterized. While six of the seven host differentials were resistant to isolates belonging to race 001 and all were resistant to 000, it is of concern that only one differential was resistant to 157 and 173 and that none of the host differentials were resistant to 177. Our approach to P. clandestina race delineation is clearly conservative and is different from previous studies. The octal nomenclature we applied in this study is not only scientifically sound but also will facilitate rapid recognition and characterization of the races.     

Characterization of <Emphasis Type="Italic">Pectobacterium carotovorum</Emphasis> subsp. <Emphasis Type="Italic">carotovorum</Emphasis> causing soft-rot disease on <Emphasis Type="Italic">Pinellia ternata</Emphasis> in China

Pinellia ternata is a traditional Chinese herb which has been used in China for over 1,000 years. A soft-rot disease characterized by water-soaked lesions and soft-rot symptoms with a stinking odour was commonly observed in cultivated fields of this plant, and Pectobacterium-like bacteria were consistently isolated from the infected tissues. Two typical strains (SXR1 and ZJR1), isolated from Shanxi and Zhejiang, respectively, were identified. Pathogenicity tests revealed that these strains were virulent to P. ternata and induced the same symptoms as observed in the field. Characterization involving fatty acid profile, metabolic and physiological properties, 16S rDNA sequence and PCR-RFLP identified both isolates as P. carotovorum subsp. carotovorum (Pcc). The 16S rDNA of both isolates shared 97–99% sequence similarity with that of Pcc strains. The phylogenetic trees showed that both isolates were clustered in the group of Pcc and P. carotovorum subsp. odorifera and both PCR-RFLP profiles were consistent with the pattern E produced by the minority of Pcc strains. Thus, isolates SXR1 and ZJR1 were characterized as Pcc in spite of some differences. This is the first report that Pcc has been proven as a causal agent of soft-rot disease on P. ternata.     

<Emphasis Type="Italic">Eremothecium coryli</Emphasis> and <Emphasis Type="Italic">E.</Emphasis><Emphasis Type="Italic">ashbyi</Emphasis> cause yeast spot of azuki bean

Yeast-like fungi were isolated from lesions on azuki bean (cv. Shin-Kyotodainagon) seeds that had been sucked by bean bugs in Kyoto Prefecture, Japan. On the basis of morphological and physiological characteristics and sequence data of the internal transcribed spacer (ITS) regions including the 5.8S rDNA, these yeasts were identified as Eremothecium coryli and E. ashbyi. Pathogenicity of those yeasts was confirmed by a reinoculation test. To our knowledge, this is the first report of the occurrence of yeast spot in azuki bean in Japan. The nucleotide sequence data reported are available in the GeneBank/EMBL/DDBJ database as accessions AB478291–AB478309 for E. coryli AZC1–19 and AB478310–AB478317 for E. ashbyi AZA1–8.     

First report of <Emphasis Type="Italic">Rhizoctonia</Emphasis> disease of lily caused by <Emphasis Type="Italic">Rhizoctonia solani</Emphasis> AG-11 in Japan

Blight on leaves, stems and bulbs of lilies grown in a greenhouse were found in Hokkaido, Japan, in 2012. Two isolates obtained from the lesions were identified as Rhizoctonia solani anastomosis group (AG)-11 based on morphology and molecular analysis. Original symptoms were reproduced after artificial inoculation with the isolates. Except for R. solani AG-2-1 and AG-4 HG-I, none of the AGs have been reported as pathogens causing lily Rhizoctonia disease in Japan; therefore, we propose adding AG-11 as a pathogen of the disease. More importantly, we report the first appearance of crop disease caused by AG-11 in Japan.     

<Emphasis Type="Italic">Colletotrichum destructivum from</Emphasis> cowpea infecting <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> and its identity to <Emphasis Type="Italic">C. higginsianum</Emphasis>

Colletotrichum isolates isolated from cowpea in the Hangzhou area of China were identified as C. destructivum based on morphological characteristics, pathogenicity tests, sequence analysis of the internal transcribed spacer (ITS)1, 5.8S RNA gene and ITS2 regions of ribosomal DNA and the infection process. The ability of the C. destructivum isolates to infect Arabidopsis thaliana was investigated under laboratory conditions and showed a two-phase hemibiotrophic infection process. In addition, the sequences of the rDNA ITS region of C. destructivum isolates from cowpea were identical with 100% similarity to that of isolates of C. higginsianum originating from cruciferous plants. This article presents new evidence in support of C. higginsianum as a synonym of C. destructivum.     

Choanephora rot of floral tops of <Emphasis Type="Italic">Hyoscyamus muticus</Emphasis> caused by <Emphasis Type="Italic">Choanephora cucurbitarum</Emphasis>

Floral rot of Egyptian henbane (Hyoscyamus muticus L.) was found on potted plants in a greenhouse in Yamaguchi city, Japan, in the late summer of 2008 and 2009. The symptoms were identical to those of rots caused by Choanephora species. The pathogen was isolated and identified as C. cucurbitarum (Berkeley and Ravenel) Thaxter. This new disease was named Choanephora rot (Kougai-kabi-byo) of Egyptian henbane.     

Anthracnose of <Emphasis Type="Italic">Enkianthus campanulatus</Emphasis> and <Emphasis Type="Italic">Rhynchosia acuminatifolia</Emphasis> caused by <Emphasis Type="Italic">Colletotrichum gloeosporioides</Emphasis> (new occurrence)

In 2003–2004, anthracnoses of Enkianthus campanulatus and Rhynchosia acuminatifolia were found for the first time in Kanagawa Prefecture and Tokyo in Japan. These pathogens were identified as Colletotrichum gloeosporioides based on their pathogenicity, morphology and ribosomal DNA spacer sequences. Results were presented at the annual meeting of The Phytopathological Society of Japan in 2004.     

The use of GFP<Emphasis Type="Italic">-</Emphasis>transformed isolates to study infection of banana with <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">cubense</Emphasis> race 4

Fusarium oxysporum f. sp. cubense (Foc) is the causal pathogen of Fusarium wilt of banana. To understand infection of banana roots by Foc race 4, we developed a green fluorescent protein (GFP)-tagged transformant and studied pathogenesis using fluorescence microscopy and confocal laser scanning microscopy. The transformation was efficient, and GFP expression was stable for at least six subcultures with fluorescence clearly visible in both hyphae and spores. The transformed Foc isolate also retained its pathogenicity and growth pattern, which was similar to that of the wild type. The study showed that: (i) Foc race 4 was capable of invading the epidermal cells of banana roots directly; (ii) potential invasion sites include epidermal cells of root caps and elongation zone, and natural wounds in the lateral root base; (iii) in banana roots, fungal hyphae were able to penetrate cell walls directly to grow inside and outside cells; and (iv) fungal spores were produced in the root system and rhizome. To better understand the interaction between Foc race 4 and bananas, nine banana cultivars were inoculated with the GFP-transformed pathogen. Root exudates from these cultivars were collected and their effect on conidia of the GFP-tagged Foc race 4 was determined. Our results showed that roots of the Foc race 4-susceptible banana plants were well colonized with the pathogen, but not those of the Foc race 4-resistant cultivars. Root exudates from highly resistant cultivars inhibited the germination and growth of the Fusarium wilt pathogen; those of moderately resistant cultivars reduced spore germination and hyphal growth, whereas the susceptible cultivars did not affect fungal germination and growth. The results of this work demonstrated that GFP-tagged Foc race 4 isolates are an effective tool to study plant–fungus interactions that could potentially be used for evaluating resistance in banana to Foc race 4 by means of root colonization studies. Banana root exudates could potentially also be used to identify cultivars in the Chinese Banana Germplasm Collection with resistance to the Fusarium wilt pathogen.     

White rust of <Emphasis Type="Italic">Ipomoea</Emphasis> caused by <Emphasis Type="Italic">Albugo ipomoeae-panduratae</Emphasis> and <Emphasis Type="Italic">A. ipomoeae-hardwickii</Emphasis> and their host specificity

In some areas of Japan, yellow spots with white pustules on leaves, stems, petioles, peduncles and calyces were found on Ipomoea nil, I. triloba, I. lacunosa and I. hederacea var. integriuscula. We demonstrated that the diseases on I. nil, I. triloba and I. lacunosa were caused by host-specific strains of Albugo ipomoeae-panduratae and defined three forma speciales of the fungus, respectively, for the three Ipomoea species: “f. sp. nile”, “f. sp. trilobae” and “f. sp. lacunosae”. Because the diseases were new to Japan, we coined the Japanese name “shirosabi-byo”, which means white rust. We also showed that the disease on I. hederacea var. integriuscula was caused by A. ipomoeae-hardwickii. We named this new disease “white rust (shirosabi-byo in Japanese)”.