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A postharvest rot of ripe sweet pepper fruits was found in Kagawa Prefecture in western Japan in October 2002. A fungus, isolated repeatedly from the diseased fruits and identified as Fusarium lactis, was demonstrated to be pathogenic on wounded fruits of sweet pepper. The disease was diagnosed as an internal fruit rot that had been noted abroad. The disease and the fungus were judged new in Japan. The fungal isolate was also pathogenic on wounded fruits of tomato and eggplant.

Brown lesions were found on leaves of the weed barnyardgrass in paddy fields in Hiroshima Prefecture in western Japan in June 2017. A fungus, isolated repeatedly from diseased plants and identified as Exserohilum oryzicola, was demonstrated to be pathogenic to barnyardgrass. The disease was diagnosed as leaf spot, reported abroad but new to Japan. In pathogenicity tests, the isolate was also pathogenic to barley, bread wheat, durum wheat, and rice but foliar symptoms were milder than on barnyardgrass; it was nonpathogenic on soybean.

Pink coloration of barley seeds has caused quality loss since 2015 in some areas where barley is grown in Japan. A bacterium, isolated frequently from the affected seeds and identified as Erwinia persicina, was demonstrated to induce the coloration. Barley was judged to be a new host for E. persicina, and this new disease was named pink seed of barley.

Cercospora blight caused by Cercospora asparagi routinely developed on asparagus in certain plastic hoop houses in Hiroshima Prefecture in western Japan every July to November. Stemphylium lycopersici was repeatedly isolated with C. asparagi from the blighted leaves in September 2016 and shown to be another causal agent of the blighting and added as another pathogen causing Stemphylium leaf spot of asparagus.

Blighting of lower sheaths was found on barley, bread wheat and durum wheat grown in western Japan in April 2014, May 2016, and April 2019, respectively. A fungus, isolated repeatedly from the diseased plants and identified as Ceratobasidium cereale, was demonstrated to be pathogenic to the three crops. The diseases, new in Japan, were diagnosed as sharp eyespot that had been noted abroad.

Fusarium asiaticum was repeatedly isolated from blighted spikes of durum wheat with head blight-like symptoms in our experimental fields in Fukuyama, Hiroshima Prefecture in western Japan, then demonstrated to be pathogenic to the crop. F. asiaticum was not previously reported as causing head blight on durum wheat, so it has been added to the pathogens causing this disease.

Many bands were detected on an electrophoretic profile of double-stranded (ds) RNA preparation from a single strain of Fusarium poae isolated from wheat. When the purified dsRNA sample was deep-sequenced by a next-generation sequencer, sixteen virus-like assembled contigs with predicted amino acid sequences showing homologies to respective viral RNA-dependent RNA polymerases (RdRps) were found by BLAST analysis. Fourteen out of sixteen sequences showed homologies to RdRps of known mycoviruses, that is, four mitoviruses, two narnaviruses, two partitiviruses, an alternavirus, a fusarivirus, a hypovirus, a victorivirus, and two unclassified mycoviruses, Sclerotinia sclerotiorum dsRNA mycovirus-L and Aspergillus foetidus slow virus 2, respectively. The other two putative viral RdRp sequences showed homologies to those of members of negative-stranded RNA viruses, the Ophiovirus and the Phlebovirus respectively, which mycoviruses had been not ever assigned to. Based on genome structure and phylogenetic analysis, both viruses were thought to be members of novel respective negative-stranded RNA virus groups. The presences of all sixteen viral RdRp sequences identified by BLAST analysis were confirmed by sequencing RT-PCR products generated from the starting dsRNA material using primers designed from the de novo assembled sequences of respective putative mycoviruses. Since the single strain of F. poae was considered to be multiply infected with mycoviruses from novel taxonomical groups in addition to many common mycoviruses, the RNA virome of the strain was found to be highly diverse.

Ear rot with white or pink mold was found on corn (Zea mays L.). A species of Fusarium, not registered previously as a pathogen causing Gibberella ear rot of corn in Japan, was isolated from the rotted ear. The isolates, identified as F. asiaticum based on morphological characteristics and nucleotide sequences, caused white or pink mold on corn ear after inoculation. Moreover, the 3-acetyl deoxynivalenol chemotype and the nivalenol chemotype were found in the isolates. We propose to include F. asiaticum as one of the pathogens causing Gibberella ear rot of corn in Japan.

A method to quantify resting spores of Olpidium virulentus, fungal vector of Mirafiori lettuce big-vein virus, which causes lettuce big-vein disease, in lettuce roots was developed using a DAS-ELISA with a polyclonal antibody against the resting spores and used to evaluate the relationship between the resting spore density in soil and disease severity. When lettuce seedlings were grown on soils containing a powder made from diseased roots with a known number of resting spores, symptoms developed from ca. 102 spores/g of soil or more. This simple method can be used in soil diagnosis and risk assessment of the disease.

Severe wilt was found on seedlings of turnip green (Brassica rapa L., perviridis group) in Ibaraki Prefecture, Japan, from May to September 2013. A fungus repeatedly isolated from diseased plants was identified as Rhizoctonia solani AG-4 HG-III based on culture morphology, anastomosis and sequencing of the internal transcribed spacer region on ribosomal DNA (rDNA-ITS region). Pathogenicity of this isolate to turnip green was confirmed based on inoculation test. Because Rhizoctonia blight of turnip green by AG-4 HG-III has not been reported so far, we propose including it as one of the pathogens causing this disease.

Severe blight of stems was found on Madagascar periwinkle (Catharanthus roseus) in Shizuoka and Okinawa prefectures, Japan, in July 2003 and September 2004, respectively. Similar fungi were isolated from the diseased plants. The isolated fungi caused the disease after inoculation and subsequently were reisolated from diseased tissues. The fungi were identified as species closely related to C. siamense or C. tropicale according to sequences of the β-tubulin-2 gene, indicating that they belong to the Colletotrichum gloeosporioides species complex. This is the first report specifying the genetic relationships of the pathogens of Madagascar periwinkle anthracnose in the complex.

Rotting of roots and stem bases and wilting of entire plants were found on a gentianaceous flowering plant, prairie gentian (Eustoma grandiflorum), grown in Kagawa Prefecture in the southwest region of Japan in April 2001. A mitosporic fungus, isolated repeatedly from the diseased plants, was identified as a species belonging to the clade 3 of Fusarium solani species complex based on the morphology and the sequence of the translation elongation factor gene. It was demonstrated to cause the disease by inoculating potted plants and reisolating the fungus from the diseased plants. We propose the name “Fusarium root rot of prairie gentian” for this disease.

Severe spotting and blight of leaves caused by Colletotrichum destructivum were found on snapdragon (Antirrhinum majus L.), a scrophulariaceous ornamental, in open fields in Shizuoka Prefecture, Japan, from June through September 2004. The fungus is added to the group of the pathogens causing anthracnose of snapdragon.

Foliar wilt as well as crown and root rot with sclerotia formation has affected potted liver leaf (Hepatica nobilis var. japonica f. magna) in Ojiya, Niigata Prefecture, Japan, since 2006. Apothecia developed from the sclerotia on soil surface of pots with the diseased plants in March. A fungus forming the apothecia was identified as Dumontinia tuberosa (Sclerotiniaceae) based on its morphology and demonstrated to cause the disease. We coined the name “Dumontinia root rot (Dumontinia-negusare-byo in Japanese) of liver leaf” for the new disease.

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)”.

A wilt disease of the model legume Lotus japonicus was observed in a greenhouse in Tokyo, Japan in May 2004. Roots of diseased plants were rotted and dark brown with lesions spreading to lower stems and leaves, resulting in rapid plant death. The causal agent was identified as Fusarium solani based on the morphology. Sequence analysis of rDNA supported the identification. Inoculation of roots of healthy plants with conidia reproduced characteristic disease symptoms, and F. solani was reisolated from lesions, satisfying Koch’s postulates. The isolate also caused chlorotic to necrotic lesions on leaves of healthy plants after wound-inoculation. Infection by F. solani of leaves of L. japonicus was confirmed histologically. Mycelia were observed in the intercellular spaces of parenchymatous tissues in the lesion area and the surrounding tissues. This is the first report of fungal disease on L. japonicus satisfying Koch’s postulates. We named it “Fusarium root rot of L. japonicus” as a new disease. The compatibility of L. japonicus and F. solani is expected to form a novel pathosystem for studying interactions between legumes and fungal pathogens.

Based on inoculation experiments and morphological studies on the pathogenic isolates of Plectosporium spp., Microdochium blight (Hakuhan-byo in Japanese) of pumpkin (Cucurbita maxima Duch.) occurring in Japan was reconfirmed to be caused by Plectosporium tabacinum, and seedling blight (Kabugare-byo in Japanese) of ranunculus (Ranunculus asiaticus L.) was demonstrated to be caused by P. tabacinum. Both diseases are renamed Plectosporium blight in this article. Some isolates of the fungus appeared to have host specificity, whereas the others had either weak or no pathogenicity to pumpkin and ranunculus.

Severe rotting and blight of seedlings of soybean, Glycine max (L.) Merr., were found in Hiroshima Prefecture in the southwest region of Japan in July 2009. A filamentous microorganism, isolated repeatedly from the diseased seedlings and identified as Pythium myriotylum, was demonstrated to be pathogenic to seedlings of soybean. The disease was new in Japan, and we propose to include this oomycete as one of the pathogens causing damping-off of soybean.

Severe spotting and blighting of leaves were found on bacopa (Sutera cordata), a scrophulariaceous ornamental, in greenhouses in Gunma Prefecture, Japan, from January through February 2007. After we isolated and identified the causal fungus as Colletotrichum destructivum and inoculated host plants with the isolate to confirm pathogenicity, we named this new disease anthracnose of bacopa.

A severe rot of postharvest fruits of sweet pepper, a variety of Capsicum annuum, was found in Kagawa Prefecture in southwestern Japan in August 1999. A fungus, isolated repeatedly from the diseased fruits and identified as Stemphylium lycopersici, was demonstrated to be pathogenic to fruits of sweet pepper. The disease was new to Japan, and the fungus was added to the pathogens causing fruit rot of C. annuum.

Severe blight of potted seedlings of monkshood caused by Plectosporium tabacinum was found in glasshouses in Kagawa Prefecture in southwest Japan in May 2001. Root rot and browning of stem bases were followed by wilting and yellowing of leaves, then blighting of leaves, flower buds and stems. A fungus was isolated from diseased plants and confirmed to cause the disease. The new disease was named “Plectosporium blight of monkshood”.

Severe wilt and blight of entire plants of yacon (Smallanthus sonchifolius) grafts on sunflower (Helianthus annuus) were found in greenhouses in Kagawa Prefecture in the southwest region of Japan from April to May between 1997 and 1999. A mitosporic fungus, isolated repeatedly from the diseased plants and identified as Botrytis cinerea, was demonstrated to be virulent to both yacon and sunflower. The new disease on yacon was named gray mold of yacon. The disease on sunflower, gray mold of sunflower, is new to Japan.

Severe wilt with spots and/or leaf and stem blight were found on a scrophulariaceous flowering plant, Nemesia strumosa, grown in Kagawa Prefecture, Japan, in February 1999. Wilted plants had numerous lesions and died early. A mitosporic fungus isolated repeatedly from the diseased plants was identified as Colletotrichum fuscum and was demonstrated to cause the disease. N. strumosa is a new host for C. fuscum, which has been known to attack foxglove (Digitalis spp.). The present disease was named “anthracnose of N. strumosa” as a new disease.

In October 1998, a disease causing mainly foliar necrotic lesions was found on African marigold (Tagetes erecta) and French marigold (T. patula) grown in Miyagi Prefecture, Japan. Similar lesions also developed on stems and flowers, resulting in early blight of the affected organs. Plants with numerous lesions withered rapidly. A mitosporic fungus isolated repeatedly from the diseased plants was identified as Alternaria tagetica and demonstrated to cause the disease. The disease, as well as the fungus, is new to Japan. We propose the name “hanten-byo”, which means leaf spot in Japanese, for this disease.

Severe spotting, blight and drop of leaves caused by Colletotrichum dematium were found on potted plants of Polygonatum falcatum, a liliaceous ornamental, in open fields in Kagawa Prefecture, Japan, in May 2001. This new disease was named anthracnose of P. falcatum.

Severe blight of stems, leaves and pods caused by Botrytis cinerea was found on pearl lupine (Lupinus mutabilis), a legume crop, grown in Kagawa Prefecture, Japan, in March–June 1996–2002. This disease was named “gray mold of pearl lupine” as a new disease.

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.

Stem rot and wilt of Jew’s marrow (nalta jute, Corchorus olitorius) were found on Is. Okinawa, Okinawa Prefecture, Japan, in March 2000. An anamorphic fungus, Lasiodiplodia theobromae was isolated repeatedly from the diseased plants and demonstrated to cause the disease. We coined the Japanese name “kurogare-byo” of Jew’s marrow for the present disease because it was new to Japan, although it had already been reported in India and Bangladesh as black band of the plant.

Severe rot of stem bases caused by Pythium aphanidermatum was found on ulluco (Ullucus tuberosus) grown in Kagawa Prefecture, Japan, in September 1999. The name “foot rot of ulluco” is proposed for this new disease.

Severe blight of stems and leaves caused by Rhizoctonia solani AG-1 (IB) was found on yacon (Smallanthus sonchifolius), a Compositae tuber crop, grown in Ehime Prefecture, Japan, from August to September 1996 and 1999. We named it “Rhizoctonia blight of yacon” as a new disease.