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Survival of Xiphinema index in Vineyard Soil and Retention of Grapevine fanleaf virus Over Extended Time in the Absence of Host Plants

First and fifth authors: Laboratoire de Virologie, Institut National de la Recherche Agronomique, Unité Mixte de Recherche INRA-Université Louis Pasteur ‘Santé de la Vigne et Qualité du Vin’, 28 rue de Herrlisheim, 68021 Colmar, France; and second, third, fourth, and sixth authors: Laboratoire de Nématologie, Institut National de la Recherche Agronomique, Unité Mixte de Recherche Interaction Plantes-Microorganismes et Santé Végétale, 400 route des Chappes, 06903 Sophia Antipolis, France

Grapevine fanleaf virus (GFLV) is transmitted specifically from grapevine to grapevine by the ectoparasitic root-feeding nematode Xiphinema index. Limited information is available on the survival of X. index in vineyard soil and on the retention of GFLV by X. index over extended periods of time. We addressed these two issues by quantifying the numbers of living X. index recovered from soil samples that were collected in three naturally GFLV-infected vineyards in France and subsequently stored at 7 or 20°C in the absence of host plants. Our data indicated a two- to eightfold decrease in X. index numbers but the recovery of 8 to 10 living fourth-stage juveniles (J4) and adults per kilogram of soil after 4 years of storage regardless of temperature. In addition, GFLV was detected readily in all groups of 20 isolated X. index adults and J4 (except for J4 that were kept 4 years at 20°C) by reverse transcription-polymerase chain reaction using total nematode RNAs and a primer set located in conserved regions at the 3′ end of viral genomic RNA 2. Our findings on the long-term survival of viruliferous X. index under adverse conditions emphasize the need for new control strategies against GFLV.