Evaluation of biotypisation assays of grape phylloxera (Daktulosphaira vitifoliae Fitch) on Vitis spp.

Grape phylloxera biotypes exist throughout viticultural regions causing substantial economic losses worldwide. The term “biotype” is used for phylloxera strains that vary in their host adaption. Numerous studies have phenotyped phylloxera biotypes, particularly regarding their performance on various Vitis spp. hosts. Our goal was to compare screening methods on their respective efficacy to provide stringent biotype definitions by performing a comparison of the applied methods. Three commonly used biotyping assays were tested employing two phylloxera strains: Biotype A adapted to V. vinifera) and biotype C (adapted to V. vinifera and rootstock hybrids V. riparia x V. berlandieri) on the partially resistant rootstock Teleki 5C (V. berlandieri x V. riparia) and V. vinifera L. cv. Riesling. 1) Simple isolation chambers consisting of rooted dormant cuttings in a perlite:peat substrate were cultivated and infested in climate chambers (25±5°C; 16h photoperiod) according to Forneck et al. (2001). 2) Excised root bio assays according to Granett et al. (1997) were performed on excised roots in Petri dishes (24°C±1°C; 16h photoperiod). 3) Sterile tissue culture plants were infested (24°C±1°C; 16h photoperiod) according to the aspetic dual culture system (Forneck et al., 1996). Life table parameters as well as plant based response (root galling) were recorded. The results of the three applied screening systems were not consistent showing that the existent biotyping assays are not comparable among them and may lead to divergent biotype assumptions. Depending on the purpose of the phylloxera screening, a combination including at least one assay involving the complete host response is recommended.

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FORNECK, A., WALKER, M. A., BLAICH, R., YVON, M. & LECLANT, F. 2001. Interaction of phylloxera (Daktulosphaira vitifoliae Fitch) with grape (Vitis spp.) in simple isolation chambers. American journal of enology and viticulture, 52, 28-34.
GRANETT, J., KOCSIS, L., OMER, A. D.,  WALKER, M. A. & LOTTER, D. Grape Phylloxera-Grape Varieties-Grape IPM.  International Symposium on the Importance of Varieties and Clones in the production of Quality Wine 473, 1997. 121-130.