In vitro Study of the Relationship Between Vitis vinifera and Eutypa lata (Pers.: Fr.) Tul. I. Demonstration of Toxic Compounds Secreted by the Fungus

Abstract

The fungus Eutypa lata (Pers.: Fr.) Tul. causes a slow plant decline in several varieties of Vitis vinifera L. In order to evaluate the virulence of the fungus and to use its toxic compounds for the selection of resistant somaclones, three types of in vitro bioassays were developed: (1) inoculation of in vitro plantlets with the fungus; (2) contact between culture filtrate and in vitro plantlets; and (3) contact between culture filtrate and excised in vitro plantlet leaves. A good correlation between the virulence of Eutypa lata isolates and the toxicity of their culture filtrate supports the possible involvement of toxic compounds in the Eutypa dieback disease syndrome. The three types of bioassay developed allow rapid assay of culture filtrate toxicity of various isolates. The excised plantlet leaves give a quick response (2 - 3 days) and reproducible results and is easy to carry out on a large scale. Further studies on the culture filtrates were performed showing, in particular, that the polysaccharide fraction was not involved in the expression of the in vitro symptoms. The expression of the resistance to E. lata in vitro is discussed.