Identification and pathogenicity of Fusarium lactis, causal agent of internal fruit rot of greenhouse sweet pepper in Alberta

Internal fruit rot of sweet pepper was found in Alberta greenhouses in 2003. White fungal mycelium covered the interior of pepper fruits and caused internal fruit rot. Research Was undertaken to Study the etiology of this new disease. Samples were collected from nine greenhouses in Alberta in 2004. Fungi from symptomatic fruits and sterns were isolated, identified, and the pathogenicity of representative isolates was confirmed following Koch's postulates. Identification of Fusarium isolates was based on cultural characteristics as well as DNA analysis of the partial sequences of translation elongation factor 1-alpha, mitochondrial small Subunit ribosomal DNA, and beta-tubulin genes. Fifty-six Fusarium isolates were collected from infected pepper fruits and steins from Alberta greenhouses in 2004 and were classified into two principal species: 32 Fusarium lactis and 18 Fusarium solani. Three isolates of Fusarium proliferatum and three isolates of Fusarium oxysporum were also identified. In pathogenicity tests, two isolates of F lactis predominately caused internal infection of fruits when flowers were inoculated with the fungus, and such infection developed slowly. An isolate of F solani caused external infection that developed rapidly on fruits. Eleven sweet pepper cultivars were evaluated for their susceptibility to F. lactis, and although all were Susceptible, the degree of susceptibility varied. Fusarium lactis was subsequently isolated and identified from infected sweet pepper fruits from greenhouses in Saskatchewan and Ontario in 2006 and 2007.