Virusfree hops and their reinfection in the field
1992
Eppler, A. (Justus-Liebig Univ., Giessen (Germany). Inst. fuer Phytopathologie und Angewandte Zoologie)
A screening of virusfree plants in hop gardens in the western part of Germany revealed a very low reinfection rate for arabis mosaic nepovirus of 1.5 % and for prunus necrotic ringspot ilarvirus of 2,6%. This reinfection was attributed to farm-dependent propagation and planting procedures. In the majority of the hop gardens no reinfection with these two viruses was observed. Despite an overall distribution of the vector of ArMV in the hop growing area of Spalt even there only 2,4 % of the samples were reinfected. Quick spread was observed for the carlaviruses hop mosaic and hop latent with 59 % and 67 %, respectively. Only for HMV and the Hallertau area an exceptional low infestation of only 20 % was observed. An explanation for this cannot be given so far. Other viruses were not found in the hop yards established with virufree planting material. The results obtained in virusfree plots surrounded by traditional hops indicate a very accelerated virus spread. As a final result the conclusion can be made, that virusfree planting material is an advantage for eliminating PNRV and ArMV when pure material is used and complete stands are established on virgin soil without virus contaminated vector populations. For the elimination of HMV and HLV with their mobil aphid vectors only the foundation of completely new hop growing areas might have a chance.
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