Espécies de Colletotrichum e Fusarium associadas a sintomas da podridão vermelha da cana-de-açúcar

Abstract

Red rot of sugarcane is one of the important fungal diseases which can result in losses of yield and quality. The causal agent is known as Colletotrichum falcatum, inducing symptoms of rot inside the stem and reddish lesions along the central part of the leaves. Another fungal disease, “Pokkah boeng”, is caused by species of the Fusarium fujikuroi species complex FFSC. Recently published results show that C. falcatum as well as Fusarium species are associated with symptoms of red rot and that symptoms sometimes overlap with those of “Pokkah boeng”. The objectives of this study were (i.) to verify if there is more than a single species of Colletotrichum associated with sugar cane plants with symptoms of red rot; (ii.) to evaluate the effect of coinfection with C. falcatum and Fusarium species on the evolution of symptoms of red rot; (iii.) to verify if also Fusarium species are able to induce reddish lesions along the central part of the leaves. Symptomatic plant material was collected in the states of Minas Gerais, São Paulo and Pernambuco in 2021, and the obtained isolates were identified by evaluation of morphological markers and molecular phylogenetic analyses of the barcode gene regions TEF, ITS, ACT and GAPDH. Pathogenicity of selected strains was tested by inoculation in stems and leaves. Fusarium madaense, F. sacchari and F. verticillioides are reported for the first time in Brazil inducing symptoms of red rot in leaves of sugarcane. A supposedly new species of Colletotrichum was identified in association with sugarcane, together with F. fredkrugeri, another member of the FFSC. Stems inoculated with F. sacchari, C. falcatum, and the combination of both, developed severe symptoms. When inoculated in leaves, F. madaense and C. falcatum induced longer lesions on the central part of the leaves compared with the other species. In conclusion, several species can cause red rot in sugarcane in Brazil. Also, Fusarium species induce symptoms of red lesions on the central part of the leaves and the association of Fusarium and C. falcatum result in the development of more severe symptoms on stems. These findings will permit the correct diagnosis of the causal agents of sugarcane red rot, and give support to breeding programs and the elaboration of adequate strategies for disease management, including the recommendation of biological and chemical products for disease control.