Rotylenchulus reniformis is a parasitic nematode that causes damage to a wide range of crops worldwide. Whereas amphimictic type reniform populations are commonly found globally, the parthenogenetic type has so far been found only in Japan with no reported damage to crops. We are interested in elucidating the relationships between the amphimictic and parthenogenic types as well as their respective pathogenicity. By using the internal transcribed spacer (ITS) of ribosomal sequences and the mitochondrial cytochrome c oxidase subunit I (mtDNA COI) gene, we aimed to characterize the two R. reniformis reproductive types in Japan, to examine the relationship between these two types, and to obtain information necessary for elucidating their pathogenicity. Both long and short rDNA ITS sequences from individual nematodes were obtained by PCR amplification and analyzed. Even within an individual, the long ITS sequences had considerably more variations than the short ITS. Phylogenetic analysis based on the ITS region revealed that each reproductive type formed a cluster in the clade for the long and short ITS sequences, respectively, except for two long ITS sequences, which were found in both reproductive types. The two long ITS sequences formed a cluster with the short ITS and seemed to be the intermediate of long and short ITS. Analyses of the mtDNA COI gene suggest that the two reproductive types of R. reniformis in Japan are within the intraspecific variation.

Ditylenchus destructor severly damages garlic production in Japan. Although it is one of the major potato pathogens in Europe, no information is available as to whether it causes any damage to potatoes in Japan. The present study aimed to examine if D. destructor from garlic could infect, propagate, and damage potatoes under laboratory conditions. The nematodes aseptically inoculated onto the tuber cubes of two major potato varieties,“ Irish Cobbler” and“ May Queen,” in Japan propagated on both varieties during an 8 weekincubation. Nematode propagation was significantly higher in the cubes pre-inoculated with the Fusarium oxysporum fungus than in those without the fungus. The nematodes inoculated directly onto the potato tuber’s surface did not infect either of the two potato varieties nor propagate in them. In pot experiments, the inoculated nematodes propagated but did not damage the tubers. These results suggest that D. destructor from garlic has a low likelihood of damaging either of the two major potato varieties in Japan.

A novel assay was developed to evaluate chemicals that exhibit antinematodal activity against mycetophagous nematodes, including the pine wilt nematode Bursaphelenchus xylophilus. This new assay was superior to the previously reported cotton ball test in terms of reproducibility and quantitativeness. In this new method, annular filter papers were used instead of cotton balls to calculate half-maximal inhibitory concentration. Morantel tartrate (MT), an antinematodal agent, was used as an indicator to confirm the efficacy of this novel assay. Results indicated that the assay procedures could be simplified without counting nematodes, and that detailed comparisons with other samples are possible. This novel assay was used to study the activity of 4-methylumbelliferone (MU) and synthetic MU glycosides. To improve the solubility of antinematodal MU in water, Mitsunobu reagent was used for glycosylation to synthesize four MU glycosides. The results of this novel assay revealed that MU had lower antinematodal activity than MT. The solubility of MU glycosides in water was improved, but their activity was reduced.

Globodera tabacum was detected only once in Japan, from an eggplant greenhouse in 1998. This species includes three subspecies, G. tabacum tabacum, G. tabacum virginiae, and G. tabacum solanacearum. The population detected in Japan (Gt-j), however, was yet to be identified at the subspecies level. Therefore, to identify the subspecies of Gt-j, we performed a PCR-RFLP test using CLAVATA3/endosperm surrounding region-related (CLE) peptidecoding genes and the sequence analysis of a pectate lyase gene. Restriction fragment patterns of the Gt-j CLE peptidecoding genes Cle1 and Cle5 were identical to those of G. tabacum tabacum. In addition, the sequence comparison of Pel1 showed more than 99% similarity between Gt-j and eight isolates of G. tabacum tabacum. Based on these results, we identified Gt-j as G. tabacum tabacum.