Doenças radiculares do alho causadas por Setophoma terrestris e Fusarium oxysporum.

Abstract

The disease known as “pink root” of garlic and onion causes considerable damage to these crops, especially in areas of continuous cultivation. The etiological agent of the disease is known as Setophoma terrestris, however, the association of Fusarium oxysporum in symptomatic plants has already been documented in onion. This disease is probably a syndrome whose etiology is still poorly understood and the etiological agents persist in the soil as saprophytes, making its management difficult. The objective of this study was to clarify the etiology of pink root of garlic in Brazil, compare root symptoms caused by Setophoma and Fusarium oxysporum and evaluate the effect of these pathogens on bulb development. From garlic samples from producing areas of Minas Gerais, Goiás and Santa Catarina, we obtained isolates of S. terrestris and F. oxysporum, which were characterized based on morphological markers and identified by molecular phylogeny analysis using the barcode regions TEF (450 bp, Fusarium) and nrSSU + nrLSU (2364 bp, Setophoma). The pathogenicity test was performed in a greenhouse with isolates representing Setophoma and Fusarium, inoculated individually and together in plants kept in pots. Inoculation was done by immersing seeds in spore suspension and by infested substrate. Plants inoculated with Setophoma developed symptoms of roots with pink coloration, progressing to necrosis, while plants inoculated with F. nirenbergiae developed root wilt, progressing to rot, restricted to roots. The incidence of Setophoma and Fusarium reduced the bulb diameter at 90 days after planting by 27% and 24% respectively and when combined, by 24%. This study confirms that both Setophoma and Fusarium cause disease in the garlic root system.