Caracterização de isolados de fusarium oxysporum associados à podridão-do-colo do maracujazeiro no estado do Ceará

Abstract

Brazil is the biggest world producer of passionfruit, and this crop has been exploited in different regions of the country. The Fusarium-root-rot and Fusarium-wilt, caused by fungal species in the genus Fusarium are within the diseases that affect the production, leading to economic losses to growers. The objective of this study was to characterize morphologically and to test de pathogenicity of Fusarium oxysporum isolates associated to passionfruit Fusarium-root-rot in the Ceará State. Passionfruit plants showing Fusarium-root-rot symptoms were collected and taken to laboratory in order to isolate the fungi associated. After the isolation in agar-agar, the isolates were transferred to potato-dextrose-agar (PDA) and spezieller nährstoffarmer agar (SNA) media, and the characteristics of colonies and morphological structures were assessed. All isolates showed typical cultural and morphological characteristics of F. oxysporum. In the pathogenicity trials two methods were evaluated: I - Immersion of roots in spore suspensions of 106 conidia . mL-1 (dipping) and II - Layer of colonized corn meal. The F. oxysporum inoculations for ten isolates were conducted in green house. The treatments were assessed regarding the number of dead plants in each method and, when plants died, they were used for reisolation in order to complete Koch's postulates. Within the ten assessed isolates, only UFCM-0447, UFCM-0449 and UFCM-0451 were pathogenic to passionfruit, inducing wilt symptom, followed by the plant death. The Fusarium-wilt occurs associated to Fusarium-root-rot on passionfruit in the Ceará State.