| Abstract: | Hop plants became infected with the hop strain of arabis mosaic virus (AMV(H)) when grown in hopfield and woodland soil in which infected plants had been growing. Infection occurred in soil infested with the dagger nematode Xiphinema diversicaudatum, but neither in uninfested soil nor in soil previously heated to kill nematodes. X. diversicaudatum transferred direct from hop soils transmitted AMV(H) to young herbaceous plants and to hop seedlings; some of the hop seedlings developed nettlehead disease. A larger proportion of plants was infected using X. diversicaudatum obtained from a woodland soil and then given access to the roots of hop or herbaceous plants infected with AMV(H). AMV(H) was transmitted by adults and by larvae, in which the virus persisted for at least 36 and 29 wk, respectively. Difficulties were encountered in detecting AMV(H) in infected hop plants, due partly to the delay in virus movement from roots to shoots. Infection of hop shoots was seldom detected until the year after the roots were infested and sometimes nettlehead symptoms did not appear until the third year. Isolates of arabis mosiac virus from strawberry did not infect hop. The results are discussed in relation to the etiology and control of nettlehead and related diseases of hop. |
