Fitotoxinas de Fusarium solani associadas a limão Cravo com sintomas de morte súbita dos citros ; Fusarium solani phytotoxins associated with Rangpur lime showing citrus sudden death symptoms

Tese apresentada à Universidade Federal de Lavras, como parte das exigências do Programa de Pós-Graduação em Fitopatologia, área de concentração em Fitopatologia para a obtenção do título de Doutor. ; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) ; Fitopatologia ; Citrus sudden death (CSD) is a plant disease associated with rootstock, which especially affects Citrus limonia (Rangpur lime) and Citrus volkameriana (Volkamerino lemon). With a symptomatology similar to tristeza disease, it is limited to northern São Paulo State and Western Minas Gerais State. Despite its economic importance, its etiology has not yet been elucidated. In the root system of a CSD symptomatic tree it is possible to observe colonization with Fusarium solani. The objective of this study was to verify if phytotoxins produced by isolates of the Fusarium solani species complex (FSSC) could play a role in the development of typical symptoms of CDS. Root-associated FSSC isolates were obtained from both apparently healthy and diseased plants and their morphological markers determined. Based on morphology and capacity for production of soluble pigments, selected isolates were cultivated on liquid Czapek-Dox culture medium and then filtered by vacuum. Culture filtrates showed toxicity in biotests to lettuce seeds, as well as to Citrus limonia twig cuts and leaves. Filtrates were also purified through TLC and submitted to spectrophotometry at 304 nm, to verify production of naphthazarins, which are phytotoxic pigments with absorbance at this wavelength. Culture filtrate of isolate CML 1152 showed the presence of 13.7 µg.mL-1 naphthazarins. Plants of Rangpur lime were exposed to culture filtrates of putative naphthazarin producers in hydroponic culture, where growth reduction, wilt, drying and leaf fall could be observed. Xylem fluids were extracted, purified trough TLC and submitted to spectrophotometry. In roots, naphthazarin contents from diseased and apparently healthy plants were similar. In the shoot, these toxin ...