Germinação carpogênica de Sclerotinia sclerotiorum (Lib.) De Bary sob resíduos e extratos aquosos de restos vegetais de culturas de inverno

Abstract

The fungus Sclerotinia sclerotiorum (Lib.) of Bary, which causes white mold in several plants of economic interest, is favored by conditions of high humidity and mild climate. Pathogen control is hampered by its survival structures that can remain viable for many years. The objective of this work was to evaluate the inhibitory and suppressive potential of extracts and residues of winter cultivated plants on the carpogenic germination of S. sclerotiorum under laboratory conditions and two sources of light. The trials were developed in the Phytopathology Laboratory of the Federal University of Grande Dourados, and the experimental design was completely randomized. Residues of crotalaria, vetch, millet, corn and niger were evaluated in two replicates with different light sources. Sclerodes of the fungus were arranged in gerbox boxes, on agar-water and covered with the respective fragmented residues. In another trial, extracts aqueous from the residues were prepared and incorporated into agar-water. The evaluations started from the formation of stipes and apotécios in the control treatment, verifying the percentage of sclerosis presenting stipes and the amount of stipes and apotécios emitted by sclerodium. Extracts of crotalaria, vetch, millet, corn and niger presented suppressive effect on the carpogenic germination of S. sclerotiorum sclerotia. Residues of crotalaria, millet, corn, and niger residues did not prevent the formation of reproductive structures by sclerotia. Sclerodes under cover with vetch residues had the germination suppressed in all replicates, regardless of the lighting regime employed in the incubation. The obtained results from the tests evaluated indicate the effect of fluorescent light as a fundamental factor in the process of differentiation of the apotécios, due to the emission of ultraviolet rays.