Nematode vectors, grape fanleaf virus (GFLV) incidence and free virus vine plants obtaining in “Condado de Huelva” vineyards zone

The « Condado de Huelva » Registered Appellation Origin Mark (RAOM) is located in the Province of Huelva, in the southwest of Andalucía (Spain), being limited by the Atlantic Ocean and the Province of Sevilla. « Zalema », a white high productive grapevine plant is its major cultivar. The predominant rootstocks used are « Rupestris du Lot », « Castel 196-17 », « Couderc 161-49 », Couderc 33-09 », « Richter 110 » and « Millardet 41-B ». Traditionally, « Zalema » cv. has been dedicated to the elaboration of amber, bouquet-flavoured wines and in the last years mainly to young, fruit-flavoured white table wines. The presence and distribution of Grapevine fanleaf virus (GFLV) and Xiphinema index and X. italiae, the main nematode-vectors of GFLV, were determined by ELISA and soil analysis, respectively. Samples were collected according to a stratified random model. The number and distribution of the samples were related to the size of each area (county) of the RAOM and dispersion of the results represented by the standard deviation (S.D.), being 2.500 and 210 the total vines and soil samples analysed in two years in the 16 counties considered. From the results, an erratic distribution of healthy plants was found, ranging from 37% (63% of infected plants) in the most attacked county to 87% of free-virus plants in the less affected. The average was close to 27%, considering the surface of vineyards and incidence in each county.

There were also high variations in the nematodes distribution, existing counties without presence of them and others with high number of populations. In average, a 6.2% of soil samples with X. index and 20.5% with X. italiae were detected. There was no relationship between the number of nematodes and the number of GLFV-infected plants in each county. Nevertheless, if the nematode free zones are not considered, the results indicate a small but appreciable relationship. The use of non-controlled GFLV-infected scions for grafting was considered as the most important way for virus transmission.The in vitro culture of apical meristems was a good method for the obtaining of free-virus plant material, reaching even a 100% of healthy plants and the non-infected plant material grew better in vitro than the infected one. When this free-GFLV plant material was used as scion for grafting in field, an increase of plant growth and production was obtained.