Keizo Katsuya

Pathogenic Races of Phakopsora pachyrhizi on Soybean and Wild Host Plants Collected in Japan

A total of 45 single uredinial isolates of Phakopsora pachyrhizi were collected from rust-infected soybean and wild host plants (Pueraria lobata and G. soja ) at different localities in central and southwestern Japan. Eighteen pathogenic races were identified using a set of differential varieties composed of nine cultivars of soybean and two accession lines of G. soja. Nine and 11 races were found on soybean and wild host plants, respectively. Two races were common to soybean and wild host plants.

Mycorrhizal association of isolates from sporocarps and ectomycorrhizas with Pinus densiflora seedlings

Thirty-two isolates from sporocarps of 27 species of macromycetes, 43 isolates from ectomycorrhizas ofPinus densiflora (Japanese red pine) and 1 isolate from an ectomycorrhiza ofQuercus myrsinaefolia were tested for the ability to form mycorrhizas withP. densiflora seedlings in glass tubes. Ten isolates from sporocarps ofHebeloma sp.,Laccaria bicolor, Lactarius chrysorrheus, Suillus granulatus, Scleroderma areolatum, Russula mariae andR. nigricans had formed ectomycorrhizas by 8 months after transplantation. Twenty isolates taken from mycorrhizas including ofCenococcum geophilum, R. mariae andR. nigricans formed ectomycorrhizas. The synthesized mycorrhizas were classified based on morphological characteristics such as hyphal arrangement of their fungal sheath, and appearance of cystidia and emanating hyphae. Twenty-one mycorrhizal types were recognized.

The disparity between the number of ectomycorrhizal fungi and those producing fruit bodies in a Pinus densiflora stand

Spatial distributions and species diversity of ectomycorrhizal fungi were studied. Epigeous fungal fruit bodies and mycorrhizas were investigated in a reforested stand of Pinus densiflora aged 45 yr. Forty species of fruit bodies, including the dominant genera, Russula and Inocybe , were recorded throughout the three-year investigation. A species-area curve of the fruit bodies indicated that mean species number in 1.5 m 2 was ca 1.0. Pine ectomycorrhiza, which were randomly sampled throughout the same investigation period, were assigned to 51 morphotypes microscopically. Although the dominant morphotypes were not manifested due to the sampling method used, a species-area curve of the mycorrhizas indicated the mean species number in 1.5 m 2 was ca 25. Thus, spatial distributions among fruit bodies and mycorrhizas were quite different, and the mycorrhizas showed more complex distributions than fruit bodies. Several species abundance and diversity coefficients changed in relation to both the calculation method and fungal material used, which suggested the necessity for a uniform method of characterizing ectomycorrhizal fungal community structure.

Potential for symbiosis of Rhizoctonia solani and binucleate Rhizoctonia with seeds of Spiranthes sinensis var. amoena in vitro

Rhizoctonia isolates obtained from non-orchid sources were tested for symbiotic ability with seeds of Spiranthes sinensis var. amoena in vitro . All or some isolates of Rhizoctonia solani anastomosis group (AG)-1, AG-2-1, AG-2-2, AG-3, AG-4, AG-5, AG-6, AG-7, AG-8, and AG-BI induced symbiotic germination of the orchid seeds. In binucleate Rhizoctonia anastomosis groups, also all or some isolates of AG-A, AG-Ba, AG-Bb, AG-B, AG-C, AG-D, AG-E, AG-F, AG-G, AG-H, AG-I, AG-K, AG-L, AG-M, AG-O, AG-P and AG-Q, induced the symbiotic germination. However, no germination occurred when the seeds were inoculated with Sebacina vermifera ( R. globularis ) and Waitea circinata ( R. zeae , and R. oryzae ) in vitro .

Morphological classification of ectomycorrhizas of Pinus densiflora

Morphological classification of ectomycorrhizas ofPinus densiflora was conducted. Fifty soil samples containing pine ectomycorrhizas, and 40 pine seedlings were collected randomly in two separate reforested stands ofP. densiflora (45 yr old) from May 1992 to October 1994. Fifty-six types of ectomycorrhizas could be classified based upon microscopically observable morphological characteristics. Fifty percent of the types showed cystidia or other specific characteristics such as laticiferous hyphae in the fungal sheaths, verrucose emanating hyphae and a positive hyphal reaction to UV irradiation. Four mycorrhizal types were confirmed to be formed by the fungiRussula delica, R. mariae, R. nigricans, andCenococcum geophilum, respectively. Although the other 52 types were unidentified mycobionts at species level, it was inferred that they were formed by the fungiHebeloma, Lactarius, Russula andTuber. There was a slight difference in the observed mycorrhizal types between the tree ages.

Vesicular-arbuscular mycorrhizal fungi in coastal dune plant communities I. Spore formation of Glomus spp. predominates under a patch of Elymus mollis

Vesicular-arbuscular (VA) mycorrhizal fungi in pure patches of coastal dune plantsElymus mollis, Wedelia prostrata andZoysia macrostachya were examined for frequency of occurrence and number of spores of VA mycorrhizal fungi over one year. Six species in three genera of VA mycorrhizal fungi were recovered. Under a patch ofE. mollis, spores ofAcaulospora sp. 1,Glomus tortuosum, Glomus sp. 1,Glomus sp. 2 andScutellospora gregaria were recovered. Spores ofGlomus spp. were most common. In patches ofW. prostrata andZ. macrostachya spores ofAcaulospora sp. 1,G. tortuosum, Glomus sp. 1,Glomus sp. 2,S. gregaria andScutellospora sp. 1 were found.

Mycorrhizal differences between genuine roots and tuberous roots of adult plants ofSpiranthes sinensis var.amoena (Orchidaceae)

Genuine roots ofSpiranthes sinensis var.amoena were infected with the mycorrhizal fungusRhizoctonia repens immediately after root formation in autumn. Infection by the mycorrhizal fungus extended, reaching a maximum the following early summer. The amount of living mycorrhizal fungus in the genuine roots dramatically declined in the flowering season, and then the roots decomposed. Tuberous roots were formed in spring. Mycorrhizas were limited to local infections and did not spread along the roots. The infection level of living mycorrhizal fungus in the tuberous roots was less than in the genuine roots throughout the year. The amount of dead fungal coils in the tuberous roots increased as the tuberous roots aged. The mycorrhizal characteritics of tuberous roots ofS. sinensis var.amoena were totally different from those of genuine roots although the tuberous roots morphologically resembled the genuine roots.

Vesicular-arbuscular mycorrhizal fungi in coastal dune plant communities : II. Spore formation of Glomus spp. predominates under geographically separated patches of Elymus mollis

Five study sites in Japan with pure patches ofElymus mollis near to the shoreline were chosen. Abundance of spore formation ofGlomus spp. underE. mollis patches were studied at four sites to understand the factors determining the development of VA mycorrhizal fungal communities at the edge of coastal sand dune vegetation. At each study site, eight soil samples from two soil depths were collected four times (three times for “Niigata”) during a year. Spores ofGlomus spp. predominated at every site, but species composition ofGlomus spp. differed from site to site. In a further experiment to measure the soil depth of the highest spore densities underE. mollis, the highest density was found at depths where rhizomes ofE. mollis were present.

Mating type of isolates derived from the spermogonial state of Puccinia coronata var. coronata

Hyphal confrontation between two haploid cultures originating from single basidiospores was used to determine the mating type ofPuccinia coronata var.coronata. Pairs of 15 single-basidiospore cultures were placed approximately 1 mm apart on the medium in all possible combinations. Hyphae of the pairs of colonies came into contact with each other in all combinations approximately two weeks after confrontations. When the nuclear number of hyphal cells in a contact zone was investigated one month after confrontation, monokaryotic hyphae were observed in selfing combination. On the other hand, dikaryotic hyphae were observed in 90.5% of crossing combinations between different cultures. Two isolates are considered compatible if dikaryotic hyphae are present in the contact zone but incompatible if they are absent. The mating type of the fungus was found to be characterized by multiple-allelomorphic tetrapolar incompatibility controlled by the “A” and “B” incompatible factors.

Fungal coil formation ofRhizoctonia repens in seedlings ofGaleola septentrionalis (orchidaceae)

Protocorms or protocorms with roots of an achlorophyllous orchidGaleola septentrionalis were inoculated with isolates ofRhizoctonia repens, R. solani, andRhizoctonia spp. The seedlings were infected with eight of twelve isolates ofR. repens. Fungal coils were formed in the cells, which was suggestive of a symbiotic association. The other isolates caused soft rot or no infection to the protocorms or the protocorms with a root.