10th INTERNATIONAL VERTICILLIUM SYMPOSIUM 16-20 ...

DISTRIBUTION OF VERTICILLIUM DAHLIAE THROUGHWATERING SYSTEMS IN IRRIGATED OLIVE ORCHARDS INANDALUCIALÓPEZ-ESCUDERO, F.J. (ag2loesj@uco.es), GARCÍA-CABELLO, S.(g3gacas@uco.es), BLANCO-LÓPEZ, M.A. (ag1bllom@uco.es).Departamento de Agronomia, Universidad de Córdoba, Campus Univ. Rabanales,Edificio Celestino Mutis, 14071, Córdoba, SpainDispersal of Verticillium dahliae microsclerotia (MS) by irrigation water hasbeen always considered very probable, although only little direct experimentalevidences were available. The aim of this research was determine the presence of V.dahliae MS in water or in soil or plant debris particles carried by water, ininfrastructures of the main pumping station of an important Irrigation Community inSouthern Spain, in an area occupied by olive orchards, in which pathogen causesVerticillium wilt of olive (VWO). Pathogen was present in all the engineeringstructures of the community involved in water transporting to irrigated plots. The studystarts in Cordobilla reservoir, from which water is pumped to the community mainchannel. Analyses of samples collected from the soil pellet decanted in this channelshowed mean ID of V. dahliae that reached 2.24 MS/gr of pellet. Pathogen ID alsoreached 1.28 Ms/gr in the pellet settled down inside the reception tank, where water isinitially gathered in the station after being taken up from the main channel. Duringwatering season, the pumping station continuously delivers water to plots. Farmersuse in the watering pipe connection in plots different kind of filters, such as sandfilters, commonly used in drip irrigated olive orchards that usually retain particlesbigger than 120 μm. We have found the pathogen in the sand of filters of several oliveorchards affected by VWO with a mean of 0.007 MS/gr of sampled sand. Moreover,fungus MS were also found in the pellet decanted is storing water ponds at these olivefields. Finally, for determining the amount of V. dahliae MS directly delivered in soilof plots through the drippers during irrigation, a similar situation was reproduced inthe pumping station installations. The simulation consisted of inserting between thestation water main a filtering system that allowed to recover particles suspended inwater 35 to 120 µm in size, to explore large water volume. Monthly analyzes of meanwater volumes of 20 m 3 allowed to detect the fungus in variable amounts that reached0.041 and 0.94 MS/m 3 during November and April, respectively. Resultsdemonstrated that V. dahliae is distributed through irrigation system, which canprovide to the pathogen a long-distance spreading in wide cultivation areas. This facthas surely contributed to increase VWO disease incidence and severity in Andalucía.80