The race status of 5 local populations of Heterodera glycines occurring in Japan was studied under the scheme given by Golden et al.(1970). “Akita 1” and “Nagano 1” populations were designated as race 3, though a slight difference was found in the reproduction rate on “PI 88788” soybean. “Hokkaido 1” and “Hokkaido 2” populations were designated as race 1. “Hokkaido 3” population was another race which was not included in Golden et al.'s scheme, and designated as race 5. “Tozan 93”, a Japanese soybean variety derived from a cross with “NC 1-2-2”, appeared to be used for differentiating race 5 from the other races.

View full abstract

The experiment was carried out to make clear the possibility that B. lignicolus establish their population in the cold northern part of Japan. Almost all individuals of larvae, adults, dispersal 3 rd stage larvae (L_III) and dispersal 4 th stage larvae were killed by being stored in water at -20°C for 1 to 5 days, but about 50 percent of L_III survived the treatment at -10°C for 5 days. The adults and L_III were able to propagate after the treatment at -20°C for 24 hours. After the treatment at -20°C the ratios of surviving L_III in the pieces of wood were higher than those in water. The number of surviving nematodes (L_III) in the logs of wood decreased slightly after the treatment at-20°C for 10 days.

View full abstract

Host finding by plant parasitic nematodes is considered to be attained partly through orientation movement within the area where host stimuli work effectively, and partly through random movement outside of this area. Blake believes that the number of nematodes aggregated around the host root at any given time is the result of a balance between the larvae continuously moving away from and those arriving to the root. On the basis of this hypothesis, a mathematical model for the changes in the number of nematodes (x) aggregated around the host at a given time (t) was presented as follows,
x=p·N/p+q·(1-e^-(p+q)t)
where N is the total number of nematodes concerned, and p and q are parameters representing the arresting and inhibiting factors of the host plant, respectively.
This model was applied to some simple in vitro experiments concerning the preferential aggregation of nematodes among some hosts with considerable accuracy.

View full abstract

Five resistance-breaking races of the root-knot nematode, Meloidogyne incognita, which were selected under high temperature conditions from three different locations were used f or comparisons in pathogenicity as well as measurements of larvae. Three tomato resistance-breaking races were found not to propagate on the resistant varieties of tobacco and sweet potato. Another two races, each of tobacco resistancebreaking and sweet potato resistance-breaking, were also found not to propagate on resistant varieties of tomato and sweet potato, or resistant varieties of tomato and tobacco, respectively. No significant differences were observed in the measurements of larvae such as body length, a-value and tail length between resistancebreaking races and common populations which had propagated on common susceptible plant under low or high temperature conditions.

View full abstract

Host plants of Meloidogyne mali from mulberry were surveyed and morphological characters of the 2nd stage larvae of the nematode were compared with those of other four species of this genus collected from mulberry plants in Japan. Six species of arboreous plants, such as elm, fig, raspberry, paper mulberry and others, were recognized as new hosts of the nematode. Although it has been reported that M. mali has no host within herbaceous plants except white clover, five species of weed plants growing in the mulberry fields and twelve species of vegetables, such as tomato, egg plant, pepper, cucumber, pumpkin, cabbage, great burdock, soybean and others, were also recognized as new hosts of the nematode in this survey. Tail length of the larvae of M. mali (ca. 34μm) was significantly shorter than those of M. arenaria (ca. 58μm), M. hapla (ca. 58μm), M. incognita (acrita) (ca. 49μm) and M. javanica (ca. 49μm), and c-value of this species (ca. 13) was larger than those of the other four species (ca. 7-8). Excretory pore of the nematode was located more anterior portion (17-18% of body length from anterior end) than those of the others (20-21%).

View full abstract

Crossonema dryum n. sp. which was found around the roots of Quercus acutissima in Kumamoto, Japan, differs from C. fimbriatum in the smaller number of body spines per annule, and more elongated tail; from C. menzeli in the location of excretory pore and the shape of body spines.

View full abstract

Five trichodorid species associated with the roots of woody plants are described and illustrated. Trichodorus tricaulatus n. sp. is characterized by its shape of posterior part of oesophageal bulb, which extends slightly over the intestine, three ventromedian cervical pores of the male, and the anterior half of spicules being striated. T. aequalis Allen, 1957, previously known only from North America, is described from central Japan. T. longistylus Yokoo, 1964, and T. kurumeensis Yokoo, 1966, are designated as junior synonyms of T. cedarus Yokoo, 1964, to which additional description is given. This species has a wide host range and probably is the most widespread trichodorid species in Japan. Paratrichodorus (Atlantadorus) porosus (Allen, 1957) was also found to parasitize a wide variety of woody plants. Variation in the number of ventromedian advulvar pores was found in several populations of this species. P.(Nznidorus) minor (Colbran, 1956) is less abundant in the study site but is considered native to Japan.
Attention is drawn to the intraspecific variation in three Trichodorus species.

View full abstract

Amino acid composition of A. besseyi propagated aseptically on alfalfa callus tissues was investigated. The nematode material comprising larvae and adults was homogenized and then separated into two parts by centrifugation; one is supernatant containing free amino acid, and the other is sediment containing tissue protein. Then, the sediment was hydrolysed to amino acid. The amounts of amino acids in the supernatant and the hydrolysate were measured with an amino acid autoanalyser. Twenty-five kinds of amino acids, 4 amins, urea, ammonia and 5 unknown ninhydrin positive compounds were detected. Of the amino acids detected, Alanine, Glutamine, Glutamic acid and Glycine from the supernatant and Glycine, Glutamic acid, Aspartic acid, Alanine, Leucine, Proline, Lysine, Valine and Serine from the hydrolysate were abundant. Analytical method of the amino acid and relation between amino acid composition and the metabolism were discussed.

View full abstract

One hundred and seventy-two plant species of 48 families including crops and weeds were tested. Among them, 168 species were found to be hosts of Pratylenchus penetrans. Plants of Leguminosae, Compositae, and Cucurbitaceae were good hosts in general. Especially, kidney bean, great burdock, lettuce, garland chrysanthemum, Japanese butterbur, onion, welsh onion, and okra were excellent hosts. While, 3 species of marigold and nut grass were not host.

View full abstract

The number of nematodes of Bursaphelenchus lignicolus and B. mucronatus aggregating to the shoot segments of Pinus thunbergii and P. taeda showed a tendency to decrease by immersing the segments in ethyl ether or ethyl alcohol. The rates of invasion into the segments were conspicuously reduced by distilled water treatment of the segments, while they were unchanged or rather increased by ethyl ether treatment. From these facts, the invasion and aggregation of these pine wood nematodes to host pine segments were considered to be regulated in different ways by host-origin substances. Another experiment revealed that ethyl ethere xtracts of the segments promoted nematode aggregation, while distilled water extracts from the segments of P. taeda repelled the nematode. Jap. J. Nematol. 9: 54-59 (1979)

View full abstract

Fusarium wilt in the tomato plants grown in the soil infested with both Meloidogyne incognita and Fusarium oxysporum f.sp. lycopersici occurred in a wilt-susceptible cultivar Matsudo-Ponderosa, but not in the other wilt-resistant cultivar Toyonishiki. The wilt symptom was severer in the plants grown in the nematode-infested soil than in those grown in the non-infested soil. In a period before the symptom appeared the rhizosphere microflora of the plants infected with nematodes changed variously in comparison to that of the non-infected plants. The population of F. oxysporum propagules was temporarily kept at a significantly high level during the early stage of the plant growth and the nematode larvae were invading into the roots, then it decreased gradually as the plants grew. Whereas the total populations of bacteria, especially including the Gram-negatives, increased drastically as the root galls developed. The rhizosphere microflora of two tomato cultivars tested changed in a similar pattern during the young period of the plant growth despite the presence of the root galls. In those plants representing wilt symptoms, there was a highly significant increase in the number of each microorganisms except Actinomycetes in the rhizosphere of the galled roots, but the number of F. oxysporum propagules varied greatly in each replicated materials. Occurrence of Fusarium wilt in the tomato seedlings inoculated with both fungus and nematode in the sterile soil was greater than in those inoculated in the non-sterile soil. Considerable increase of Gram-negative bacteria and reduction of F. oxysporum propagules were characteristic in the rhizosphere microflora of the tomato seedlings inoculated with both pathogens in the non-sterile soil, while it was not recognized in that of the seedlings inoculated with the fungus alone.

View full abstract

A few nematodes were found in the healthy roots of the chestnut seedlings inoculated with a large number of Pseudhalenchus anchilisposomus in the steamsterilized soil. While the number of nematodes in the declining roots of the seedlings grown under a hyper-moist soil condition was much higher than that in the healthy roots grown under ordinary condition. The nematodes were detected intercellularly in the cortical tissues and the branching portion of the roots, but they were not observed in the xylem. Sometimes the coiled nematodes remaining in the cortical cells of the declined roots were recognized. Certain symptoms associated with the dark-spoted granulation of the cell contents were observed occasionally in the cells in which the nematodes had established and in a few surrounding cells.

View full abstract