Characterization of three cysteine-rich proteins and an elongation factor from the secretome of Fusarium graminearum

Fusarium graminearum is one of the primary causal agents of Fusarium head blight (FHB) in cereals. Most proteins in the secretome of this pathogen are uncharacterized and their role in FHB is undefined. This study was aimed at elucidating the roles of four secreted proteins in F. graminearum growth and aggressiveness; a cerato-platanin, FgCPP1, two CFEM-containing proteins, FgCFEM1 and FgCFEM2 and the elongation factor 1A (FgEF1A). Characterization of gene disruption and in locus overexpression (OX) transformants for these proteins showed that CPP1-OX produced more DON in culture and also caused higher initial infection in different wheat cultivars. CFEM1-OX accumulated less DON in culture but showed increased disease spread in a moderately susceptible wheat cultivar. FgEF1A overexpression did not lead to substantially higher FgEF1A expression; nevertheless, a reduction in fitness and aggressiveness was observed. This study provides some basic insights into the roles of these secreted proteins in F. graminearum aggressiveness

Characterization of Novel Trichoderma asperellum Isolates to Select Effective Biocontrol Agents Against Tomato Fusarium Wilt

The use of novel isolates of Trichoderma with efficient antagonistic capacity against Fusarium oxysporum f. sp. lycopersici (FOL) is a promising alternative strategy to pesticides for tomato wilt management. We evaluated the antagonistic activity of 30 isolates of T. asperellum against 4 different isolates of FOL. The production of extracellular cell wall degrading enzymes of the antagonistic isolates was also measured. The random amplified polymorphic DNA (RAPD) method was applied to assess the genetic variability among the T. asperellum isolates. All of the T. asperellum isolates significantly reduced the mycelial growth of FOL isolates but the amount of growth reduction varied significantly as well. There was a correlation between the antagonistic capacity of T. asperellum isolates towards FOL and their lytic enzyme production. Isolates showing high levels of chitinase and β-1,3-glucanase activities strongly inhibited the growth of FOL isolates. RAPD analysis showed a high level of genetic variation among T. asperellum isolates. The UPGMA dendrogram revealed that T. asperellum isolates could not be grouped by their anta- gonistic behavior or lytic enzymes production. Six isolates of T. asperellum were highly antagonistic towards FOL and potentially could be used in commercial agriculture to control tomato wilt. Our results are consistent with the conclusion that understanding the genetic variation within Trichoderma isolates and their biochemical capabilities are required for the selection of effective indigenous fungal strains for the use as biocontrol agents

Enniatin Production Influences Fusarium avenaceum Virulence on Potato Tubers, but not on Durum Wheat or Peas

Fusarium avenaceum is a generalist pathogen responsible for diseases in numerous crop species. The fungus produces a series of mycotoxins including the cyclohexadepsipeptide enniatins. Mycotoxins can be pathogenicity and virulence factors in various plant–pathogen interactions, and enniatins have been shown to influence aggressiveness on potato tubers. To determine the role of these mycotoxins in other F. avenaceum–host interactions, ENNIATIN SYNTHASE 1 (ESYN1) disruption and overexpression mutants were generated and their ability to infect wheat and peas investigated. As a preliminary study, the transformants were screened for their ability to cause potato tuber necrosis and, consistent with a previous report, enniatin production increased necrotic lesion size on the tubers. By contrast, when the same mutants were assessed in their ability to cause disease in pea roots or durum wheat spikes, no changes in disease symptoms or virulence were observed. While it is known that, at least in the case of wheat, exogenously applied enniatins can cause tissue necrosis, this group of mycotoxins does not appear to be a key factor on its own in disease development on peas or durum wheat