Epidemiological studies on lethal redness disease occurring in strawberry crops in Argentina.

FERNÁNDEZ, F; MENEGUZZI, N.G; KIRSCHBAUM, D.; GALDEANO, ERNESTINA; CONCI, V. C.; CONCI, L. R.

Roma

Congreso; 22nd ‘International Conference on Virus and Other Graft Transmissible Diseases of Fruit Crops; 2012

ICVF

In strawberry (Fragaria x ananassa D. cv camarosa) plants, the lethal redness symptom is characterized by stunting, curled leaves and redness on the abaxial face, followed by a generalized decline, necrosis and subsequent death of the plant. These symptoms cause yield losses by preventing proper fruit development. Previous work reported the association of those symptoms with at least two different phytoplasmas. The strawberry read leaf phytoplasma (16SrXIII, subgroup E) and the strawberry X-disease phytoplasma (16SrIII) vwhich have been reported exclusively associated with strawberry in Argentina. The aim of this work is study the relationship between those and other phytoplasmas, with the symptoms described and to determine the incidence and prevalence of the described symptom and the percentage of diseased plants, in strawberry crops in Argentina. During the period 2010-2011 40 plots of strawberry fields located in Lules (Tucumán province, Northwest Argentina), the most important production region in Argentina, were sampled. Incidence (I= Nº of plants with symptoms/Nº total of plant counted), prevalence (P= presence of at least 1 plant with symptoms per plot /Nº total of plots analyzed) and percentage of infected plants (No. of PCR-positive samples for phytoplasmas/No. of symptomatic plants analyzed) were determined. In each sampled plot, transects constituted by 100 plants (300 x ha) were randomly laid. Each symptomatic plant was analyzed by PCR. Our result shows that the strawberry lethal redness is present with a 62% of prevalence and low incidence (0.45%) in strawberry production areas. We also demonstrate that the described symptoms are not always associated with phytoplasma infection, since only 7.96% of them were positive by PCR, suggesting the presence of other pathogens or abiotic stresses involved. It is necessary to continue the surveys in production areas and it would be important to study these symptoms in nurseries where strawberry seedlings are produced.