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

ABSTRACT 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 degrees 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 degrees 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.