We investigated the characteristics of desaturation in Trichoderma sp. AM076. Although 6,9,12-octadecatrienoic acid (18:3ω6) was detected when Trichoderma sp. AM076 was cultivated in the presence of 6,9-octadecadienoic acid (18:2ω9), the desaturation products of 6,9,12-octadecatrienoic acid (18:3ω6) and 6-octadecenoic acid (18:1Δ6) were not detected. These results suggest that the double bonds at the Δ6 position of 18:3ω6 and 18 :1Δ6 disturb their Δ15 and Δ9 desaturation, respectively. This fungus also introduced a double bond at the Δ15 position of 9,12-hexadecadienoic acid (16:2ω4), thereby yielding a novel C16 polyunsaturated fatty acid (PUFA) identified as 9,12,15-hexadecatrienoic acid (16:3ω1). Further investigations revealed that the mutant having enhanced accumulation of linolenic aid (18:3ω3) accumulates 16:3ω1 as one of the major PUFAs, together with 9,12-octadecadienoic acid (16:2ω4), when grown with palmitoleic acid (16:1ω7). These results suggest that, in this strain, the reaction that catalyzes the conversion of linoleic acid to linolenic acid, similar to the conversion of 16:2ω4 to 16:3ω1, is not ω3 desaturation but Δ15 desaturation.

A community of arbuscular mycorrhizal (AM) fungi was investigated in a warm-temperate deciduous broad-leaved forest using a molecular analysis method. Root samples were obtained from the forest, and DNA was extracted from the samples. Partial 18S rDNA of AM fungi were amplified from the extracted DNA by polymerase chain reaction using a universal eukaryotic primer NS31 and an AM fungal-specific primer AM1. After cloning the PCR products, 394 clones were obtained in total, which were divided into five types by restriction fragment length polymorphism (RFLP) with HinfI, RsaI, and Hsp92II. More than 20% of the clones were randomly selected from each RFLP type and sequenced. Phylogenetic analysis showed that all the obtained clones belonged to Glomus but could not be identified at species level. Topsoil of the forest containing plant roots was inoculated to nonmycorrhizal seedlings of indigenous woody plants, Rhus javanica var. roxburghii and Clethra barvinervis, to introduce the community of AM fungi into the seedlings. Among these five RFLP types, four types were detected from both seedlings, which indicates that the AM fungal community in the forest root samples was introduced at least partly into the seedlings. Meanwhile, an additional four types that were not found in the forest root samples were newly detected in the seedlings, these types were closely related to one another and close to G. fasciculatum or G. intraradices. It is expected that a community of indigenous diverse AM fungi could be introduced into target fields by planting these mycorrhizal seedlings.

Umbelopsis ramanniana is a well-known species in this genus. A characteristic morphological feature of this fungus is the remarkable variation in the sporangiospore shape, which implies the genetic variations occur in the nucleotide sequences of the internal transcribed spacer (ITS) regions of the nuclear ribosomal DNA (nrDNA) in the U. ramanniana isolates. The relationship between the variations of the sequences of the nrDNA ITS regions and those of the sporangiospore morphology was investigated for 12 isolates of U. ramanniana collected in Europe. Neighbor-joining and parsimony analyses on the sequences suggested that these isolates split into three groups. Precise examination of the morphology showed that the isolates of those respective groups were different from each other in their sporangiospore shape. The present study implies at least three intraspecific groups exist in U. ramanniana and that the variations in the nucleotide sequences of the nrDNA ITS regions correlate well with those in the sporangiospore shape in these intraspecific groups.

In the third report of the present series, four new and noteworthy plant-inhabiting fungi are described and illustrated. Pseudodidymaria symplocarpi on Symplocarpus nipponicus is reported as a new species. Cheirospora botryospora and Exosporium mexicanum are new to Japan. Pittosporum tobira is a new host plant for Flosculomyces floridaensis.

Changes in the fatty acid composition of docosahexaenoic acid (DHA)-producing Schizochytrium limacinum SR21 were investigated. The addition of cyanocobalamin, which is an active component of vitamin B₁₂, decreased the content of odd-chain fatty acids such as pentadecanoic acid (C15:0) and heptadecanoic acid (C17:0). Cyanocobalamin may upregulate the cobalamin-dependent methylmalonyl-CoA mutase, which converts propionic acid to succinic acid, thereby decreasing the content of odd-chain fatty acids. The addition of p-toluic acid resulted in a decrease in docosapentaenoic acid (DPA, 22:5n-6) content and an increase in eicosapentaenoic acid (EPA, 20:5n-3) content in a dose-dependent manner. Two additional peaks of fatty acids, characterized as Δ4,7,10,14-eicosatetraenoic acid (20:4n-7) and Δ4,7,10,14-docosatetraenoic acid (22:4n-9), were detected.

Entyloma species causing white smut disease of Cosmos species have been studied. Two species can be recognized, Entyloma holwayi on C. caudatus and C. sulphureus from North America, and E. cosmi sp. nov. on C. bipinnatus from Japan and Europe.

Dinemasporium longicapillatum sp. nov., isolated from a decaying leaf of sugar cane collected in Irabujima island, Japan, is described and illustrated. It is similar to D. strigosum and D. strigosulum in conidial length/width ratio, but differs mainly in its smaller conidia and longer conidial appendages.

Genetic relationships in a natural Japanese population of Pleurocybella porrigens were determined based on ITS sequence data. In a UPGMA similarity tree, all sequences of 23 specimens from 13 different geographic origins were grouped into two distinct clusters (groups A and B). Sequence variation of the ITS region between groups A and B consisted of 33-40 nucleotides, corresponding to 5%-6% of their total length, and specific nucleotide variations characterizing groups A and B were found. Although these results did not show correlation with differences of substrates for fruiting and geographic origins of the specimens, it was suggested that P. porrigens distributed in Japan include at least two genetically different populations.

The leaf blight and mummy fruit disease fungus of Prunus ssiori in northern Japan is newly named M. ssiori, as a fourth member in the M. padi group of section Disjunctoriae of the genus Monilinia (Sclerotiniaceae). It has been misidentified with Monilinia kusanoi, but recent studies show it is different from M. kusanoi as well as other related species on prunaceous hosts in respect to host relation, pathogenicity, morphology, and gene analysis.