Transmission of the California Tobacco Rattle Virus (CTRV) by Three Species of the Nematode Genus Trichodorus

Abstract

The California tobacco rattle virus (CTRV), serologically related to the Dutch strains of TRV, was successfully transmitted by three species of the nematode genus Trichodorus Cobb, 1913. Trichodorus christiei Allen, 1957 (Riverside and Shafter isolates) and T. porosus Allen, 1957, were moderately good vectors when California Wonder pepper and Glurk tobacco, respectively, both poor hosts for the nematodes, were used as sources of virus and as bait plants. Trichodorus allius Jensen, 1963 was an excellent vector and was used in all experiments on nematode-virus interrelationships. Ten nematodes were sufficient to transmit CTRV to 100 percent of the bait plants, Nicotiana glutinosa, while one and five nematodes transmitted the virus to 60 and 80 percent of the bait plants, respectively. When Glurk tobacco (Nicotiana tabacum var. Xanthi-nc) was used, all the stages of T. allius transmitted the virus with almost equal efficiency. Ten nematodes of any stage, the three larval stages and the adult females, provided 100-percent transmission; five nematodes of any stage except third-stage larvae produced similar results. When single nematodes were used, percentage transmission was as follows; Adult females, 100, second-stage larvae, 50, fourth-stage larvae, 33.3; and third-stage larvae, 16.7. When 50 nematodes per pot were used, Trichodorus californicus Allen, 1957 did not transmit CTRV. Populations of T. allius became infective after feeding on virus-infected Glurk tobacco for 1 hour. Efficiency increased as the feeding time was increased up to 24 hours. An infective population transmitted CTRV within 1 hour after being added to the roots of a bait-plant, and efficiency of transmission increased up to 48 hours. Evidence for transovarial transmission and transtadial passage of the virus was not conclusive. Populations remamed infective for 20 weeks when kept at 20°C. without a host and 27 weeks when feeding on a virus-immune host. Virus was recovered directly from cut nematodes when their body contents were rubbed on leaves of cowpea, Vigna sinensis (Tomer) Savi.