Several cultivars of radish (Raphanus sativus) and white mustard (Sinapis alba) as a trap crop have been developed in Europe to control Heterodera schachtii. In this study, an inoculation test was carried out to find out whether there is a trap crop of H. schachtii among green manure crops such as radish and white mustard available in Japan. H. schachtii did not multiply on the radish ‘Kobuberi-daikon’ among the test cultivars and ‘Kobuberi-daikon’ was not effective in increasing the nematode population density in soil. As a result, it was concluded that the radish‘ Kobuberi-daikon’ may be a trap crop of H. schachtii.

In this study, phylogenetic analysis was performed based on nearly full-length sequences of the 18S ribosomal RNA (rRNA) gene and 5.8S rRNA gene/internal transcribed spacer (ITS) region of the plant-parasitic nematodes Hirschmanniella diversa and H. imamuri and other related taxa. The analysis placed H. diversa and H. imamuri in Clade I with 3 known species, namely, H. santarosae, H. pomponiensis and H. gracilis. Among the hosts of these nematodes, families Poaceae and Typhaceae were consistent among H. diversa and the 2 species in Clade I. Phylogenetic analysis based on the 5.8S rRNA gene/ITS region suggests that Hirschmanniella spp. in all clades can parasitize family Poaceae. Interestingly, although H. imamuri and H. oryzae are both rice (Oryza sativa) root-parasitic nematodes, they were placed in Clade I and Clade III, respectively, indicating that they have different evolutionary histories.

A population of sugar beet cyst nematode, Heterodera schachtii (HS), was first detected in 2017 in a Brassicaceae crop field in Hara village of Nagano Prefecture in central Japan. The village is known for highland summer vegetable production. Currently, emergency control measures have been introduced prohibiting cultivation and exportation of potential host crops, and requiring soil fumigation. After HS is controlled, a new farming system based on crop rotation and use of catch crops is needed for prevention of HS recurrence and rapid resumption of cultivation. Reportedly, HS has a wider host range compared with other cyst nematode species, and the range may differ among populations. Thus, for development of a farming system, information on the host range of the HS population is essential. In this report, we provide information on the host range of the HS population. Several inoculation experiments were conducted with a total of 17 crops and 106 cultivars, mainly crops commonly grown or can be grown in Hara village. Broccoli, cabbage, cauliflower, Chinese cabbage, radish, swiss chard, sugar beet and spinach were good hosts. Among the tested crops, resistant cultivars were not found. Tomato and buckwheat were considered moderate and poor hosts, respectively. Lettuce, maize, zucchini, celery, parsley, lacy phacelia (landscape plant) and clover were non-hosts. We found an individual susceptible plant among the commercial seeds of the leafy radish cultivar, which has been reported to be resistant to HS and used as a catch crop.