Linhagens filogenéticas do complexo Fusarium oxysporum e Fusarium udum associadas à murcha do maracujazeiro

Abstract

Sour and sweet passion fruit are species of the genus Passiflora widely cultivated in Brazil. Among the most important diseases is Fusarium wilt, whose causal agent is known as Fusarium oxysporum f. sp passiflorae. This disease is of great economic importance in areas with sandy soils and is transmitted from one orchard to another through infected seedlings, and between plants by contact between roots and irrigation water. Preliminary studies have shown that most formae speciales of the Fusarium oxysporum species complex FOSC do not represent monophyletic groups, while ot her pathogens with morphological characteristics similar to Fusarium oxysporum cause wilt. In this context, we formulated the hypothesis that formae specialis that causes wilt in passion fruit is represented by distinct phylogenetic lineages and that there is more than one species associated with wilting of passion fruit in Brazil. Forty-six isolates from plants wilt symptoms were evaluated by phylogenetic analysis of the TEF-1 region, sexual compatibility tests, morphological markers and pathogenicity tests.The results obtained through phylogenetic analysis of TEF-1 region showed that three different phylogenetic lineages of the FOSC are associated with wilting of passion fruit. Isolates obtained from passion fruit also grouped with reference material of Fusarium udum, a species belonging to Fusarium fujikuroi species complex FFSC.The pathogenicity test demonstrated that isolates from all three different lineages of the FOSC and F. udum induced wilt symptoms in passionfruit and six other plants tested:Solanum lycopersicum, Phaseolus vulgaris, Gossypium hirsutum, Cucumis sativus, Cajanus cajan and Crotalaria ochroleuca.There are no morphological markers which help to separate different lineages of the FOSC and F. udum.From crosses with F. udumtesters strains and isolated obtained from the field, it was possible to identify the mating type and to induce the formation of fertile perithecia, confirming the identity of the pathogen.Fusarium udum is recorded for the first time as a pathogen of Passiflora and other evaluated plants. The supposed specificity of formae speciales is not confirmed, as the isolates caused disease in all tested plants.The results will support a more objective diagnosis of the etiological agent of Fusarium wilt, including its incidence, geographical distribution and host range. Future research aiming at the selection of genotypes with resistance to wilt will also be guided by these findings.