Fungos associados à podridão e à síndrome da murcha em cana-de-açúcar

Abstract

With the ban on burning, sugarcane cultivation faces new challenges in the control and management of fungal diseases previously considered secondary. Increasing losses have been recorded during periods of water deficit due to the higher incidence and severity of Red Rot and Rind Rot, leading to stalk drying, wilting, and rotting, resulting in reduced productivity and sugar quality. In the 2023/2024 growing season, a phenomenon called Sugarcane Wilt Syndrome (SWS) was also observed, characterized by the simultaneous association of Phaeocytostroma, Colletotrichum, and Fusarium. The main etiological agent of SWS remains unknown, but its occurrence is attributed to climatic conditions, such as prolonged drought, which significantly influence the progress of the syndrome.The objectives of this study were to: (i) identify the fungi associated with Rind Rot and Sugarcane Wilt Syndrome (SWS) through morphological evaluation and molecular phylogenetic analysis; (ii) test the pathogenicity of representative isolates of the species found; and (iii) describe and document the symptoms observed in the field and in pathogenicity tests. In samples collected from the states of MG, GO, PE, and MS, the fungi Phaeocytostroma sacchari, Colletotrichum falcatum, and species of Fusarium from the F. fujikuroi complex were found associated with symptoms of Rind Rot and Wilt Syndrome. Based on morphological markers, Phaeocytostroma and C. falcatum were identified. Through phylogenetic analysis of DNA sequences from ITS, LSU, and EF-1α regions, seven isolates were identified as P. sacchari. The pathogenicity of P. sacchari and C. falcatum isolates was tested individually and in combination. Both fungi induced Red Rot symptoms in detached stalks, with P. sacchari alone causing less severe symptoms compared to the other treatments. In tests using detached leaves, only C. falcatum and the combination of both fungi induced Red Rot symptoms. With the method used, it was not possible to reproduce symptoms of wilting and stalk desiccation. Further tests should be conducted to clarify the causes of SWS onset. The information generated may contribute to plant health management and support breeding programs for resistant varieties