Viruses, viroids and MLOs in Japan
In citrus, satsuma dwarf nepovirus (SDV) and citrus tatter leaf ' virus ' (CTLV) are spreading in Japan (M. Koizumi, Fruit Tree Research Station, Shizuoka 420-02; abstract 9 of Appendix on FFTC Symposium). dsRNA analysis is being used to detect these viruses and also citrus tristeza closterovirus (EPPO A2 List) and citrus rugose leafilarvirus (T. Kano et al., same address; abstract P. I-1-11).
In apple, the agent of dapple apple and scar skin disease has been identified and named as apple scar skin viroid (H. Koganezawa & J. Hashimoto, Fruit Tree Research Station, Morioka 020-01; abstract P. I-2-98). Strains of hop stunt viroid have been found infecting plum and peach, as well as hop, grapevine, cucumber and citrus (as previously reported in Japan and in EPPO region) (T. Sano et al., Faculty of Agriculture, Sapporo 060; abstract St.I.-7-2). These two viroids can be detected by return-gel electrophoresis (S. Saito et al., Faculty of Agriculture, Iwate University, Morioka 020; abstract P. I-2-108).
In a survey of strawberry viruses, strawberry mild yellow edge luteovirus was detected in 66 % of plants and strawberry mottle 'virus' in 60 %. Strawberry vein-banding caulimovirus (EPPO A2 List) was rare, and strawberry crinkle rhabdovirus was not found. Other diseases were pseudo mild yellow edge, necrotic shock and vein-yellowing. EM studies showed nucleus-associated rhabdovirus particles in plants infected by strawberry latent C 'virus' (EPPO Al List) and carlavirus particles in plants affected by pseudo mild yellow edge (N. Yoshikawa & T. Inouye, Faculty of Agriculture, Iwate University, Morioka 020 and College of Agriculture, University of Osaka, Sakai 591; abstract P.I-1-32).
In grapevine, the most important viruses are all phloem-limited: grapevine Ajinashika virus (GAV) and grapevine stunt virus (GSV) (both small and spherical about 25 nm) and grapevine leafroll virus (GLRV), probably a closterovirus (S. Namba et al.; Faculty of Agriculture, Tokyo University, Bunkyo-ku, Tokyo 113; abstract P. I-1-57). IEM can be used to detect GLRV in grapevine leaves, while ELISA can be used for GAV (J. Takahashi et al.; Suntory Ltd. Institute f or Fundamental Research, Mishima, Osaka 618; abstract P. I-1-8).
Among the most important plant disease MLOs in Japan are mulberry dwarf MLO, paulownia witches’ broom MLO and cryptotaenia witches' broom MLO. The last is transmitted by Macrosteles striifrons and affects many vegetables as well as Cryptotaenia japonica (carrot, lettuce, spinach, onion, etc.). (Y. Doi et al.; Faculty of Agriculture, Tamagawa University, Machida, Tokyo 194; abstract St. II-5-1).
Sources
Abstracts of the 5th International Congress of Plant Pathology, Kyoto (JP), 1988-08-20/27