An Integrated Evaluation of Mycoparasites from Organic Culture Soils as Biological Control Agents of Sclerotia of Sclerotinia Sclerotiorum in the Laboratory

Abstract

Sclerotinia sclerotiorum is one of the most harmful phytopathogens in agriculture. They form sclerotia which render them resistant and persistent. Crop protection is necessary and mycoparasites are a friendly and efficient alternative to chemicals, when used as Biological Control Agents (BCAs). In this work, one hundred ninety nine candidate mycoparasites from soils of organic crops in Southwestern Greece were isolated by using the method of trapping. After preliminary evaluation the best eighteen were selected and subjected to further evaluation. The mycoparasites were applied in the form of hyphae and spore suspension and were tested in water agar, sterile and non-sterile soil. Mycoparasites produced good results to the control of sclerotia of Sclerotinia sclerotiorum. In particular, the isolate G21-3 (Gliocladium sp.) proves to be an exceptional mycoparasite and a competent antagonist as well. Mycoparasites differ in effectiveness not only among them but, moreover, each one of them demonstrates different effectiveness in different environments. Effectiveness decreases significantly from the hyphae in water agar to the impregnation by spore suspension in sterile and non-sterile soil. In non-sterile soil the effectiveness of all the mycoparasites, except for G21-3, is minimal (close to zero). The antagonism of the existing soil microflora is a highly significant factor. The ideal period to isolate aggressive mycoparasites of sclerotia of Sclerotinia sclerotiorum from soil paste is 15 days. Preliminary evaluation in water agar followed by a two- week period of incubation proves to be a very good instrument in the preliminary process evaluation of a large number of candidate mycoparasites. The evaluation experiments, presented in this work, constitute an integrated methodology for the evaluation of candidate mycoparasites of sclerotia of Sclerotinia sclerotiorum species in the laboratory. They provide an excellent, economic and fast protocol for selecting the appropriate strain as Biological Control Agent (BCA), while minimizing the work and time in the field.