The geographical distribution of the clover cyst nematode Heterodera trifolii in eastern Japan on white clover (Trifolium repens) and greenhouse carnation (Dianthus caryophyllus) was surveyed in 2012. A total of 195 and eight soil samples were collected from the rhizospheres of white clover and greenhouse carnation in eastern Japan, respectively. Second-stage juveniles (J2s) of cyst nematodes were detected in 57 of the 195 samples of white clover (29.2%) and five of the eight samples of greenhouse carnation (62.5%) by the Baermann funnel method. The cyst nematodes were identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the internal transcribed spacer (ITS) region of the nuclear ribosomal RNA (rRNA) gene by using digestion patterns of AluI, MseI, and RsaI. Consequently, H. trifolii was detected from 56 of the 195 samples of white clover (28.7%) and five of the eight samples of greenhouse carnation (62.5%). Our results showed that H. trifolii is widely distributed in eastern Japan and can be potentially a serious threat to carnation production.
Sugarcane yield in Japan has continuously decreased by 17% over the past 20 years. The objective of this study was to quantify the sugarcane yield loss caused by plant-parasitic nematodes (PPN) under field conditions in Japan. We set up 15 plots in a sugarcane field in Kitadaito, Okinawa, and assigned them to nematicide-treated (fosthiazate, 3 kg (×0.7) and 7.5 kg (×1.7) per ha) and non-treated control plots in 5 replicates. Initially, the numbers of lesion nematodes (Pratylenchus zeae) did not differ significantly among the three treatments, but were significantly lower in ×1.7 fosthiazate than in the control after 3 and 5 months. Sugarcane yield in 12 months was significantly higher by ca. 15% in both the ×0.7 and ×1.7 nematicidal treatment (55 t/ha) plots than in the control (48 t/ha) plots. The results implied that the lesion nematode may suppress the number of tillers in the early stage, resulting in yield reduction.
Root-knot nematodes (Meloidogyne spp.) were surveyed from suitable wild herbaceous plant hosts in non-crop fields at an elevation of less than 200 m of northwest Kyushu by pulling out and observing the root systems for galls. Nematodes were detected in 10 out of 49 surveyed sites (20%): M. hapla in nine sites and M. incognita in one site. Nematodes were identified by perineal patterns of adult females or size of amplicon of partial mitochondrial DNA. Our survey suggests that M. hapla is the predominant species in non-crop fields in northwest Kyushu.
A newly bred, common oat cultivar Sniper, which has originated from Tachiibuki, a known fall forage cultivar that suppresses root-knot nematodes damage to succeeding crop of sweet potatoes, was tested to examine its susceptibility to five major nematode species which were distributed in upland of Kyushu, Japan. Sniper showed poor host suitability to the four Meloidogyne species in a pot experiment. Meanwhile, its host suitability for Pratylenchus coffeae was similar to that exhibited by other common oat cultivars examined in this study.
To establish an easy axenic culture method for Steinernema carpocapsae and to understand the nutrition provided for nematode growth and propagation produced in the insect cadaver, we tested several supplementations to axenic liquid cultures. S. carpocapsae grew but reproduced poorly on the liquid static axenic culture developed for bacterial-feeding nematodes; however, supplementation by S. carpocapsae-infected insect cadavers sterilized by autoclaving largely improved nematode growth and propagation. These results suggest supplementation of the cadaver is a useful method to improve axenic culture and the autoclaved nematode-infected insect contains important heat-stable nutritional factors for the growth and reproduction of S. carpocapsae.