Potential environmental fate of elsinochrome A, a perylenequinone toxin produced in culture by bindweed biocontrol fungus Stagonospora convolvuli LA39

Abstract

The photosensitizing perylenequinone toxin elsinochrome A (EA) is produced in culture by the bindweed biocontrol fungus Stagonospora convolvuli LA39 where it apparently plays a pathogenicity related role. We investigated the fate of EA with reference to its stability under different temperature and light conditions. EA remained stable when boiled in water at 100°C for 2 h. Similarly, exposing EA to 3-27°C in the dark for up to 16 weeks did not affect its stability either in dry or in aqueous form. However, results from irradiation experiments indicate that direct photolysis may be a significant degradation pathway for EA in the environment. EA either in dry form or dissolved in water was degraded by different irradiation wavelengths and intensities, with degradation plots fitting a first order rate kinetics. EA degraded faster if exposed in aqueous form, and at higher quantum flux density (jsmol s F m-2). Sunlight was more effective in degrading EA than artificial white light and ultraviolet radiations (UV-A or UV-B). Exposing EA to natural sunlight, particularly, during the intense sunshine (1,420-1,640 ismol s 2) days of 30

ISSR fingerprinting for the assessment of the bindweed biocontrol agent Stagonospora convolvuli LA39 after field release

“…We therefore conclude that this strain will not result in populations dense enough to have negative effects on the environment and other organisms in the longer term. These findings significantly add to earlier studies of our research group corroborating the potential of S. convolvuli LA39 as an efficient and risk‐free biocontrol agent (Ahonsi et al. 2006; Boss et al.…”

Elsinochrome A production by the bindweed biocontrol fungus Stagonospora convolvuli LA39 does not pose a risk to the environment or the consumer of treated crops

“…This concentration is 125 times lower than the LOEC for the most sensitive organism (Trichoderma atroviride, 5 ng mL À1 ), and thus far too low to be of any risk for the consumer. When estimating the risk of residues in agricultural products it must also be taken into account that normally the last mycoherbicide treatment is applied several weeks before harvest and that ELA is rapidly degraded by sunlight, as was demonstrated by Ahonsi et al (2006). They observed that ELA applied to an inert surface was degraded rapidly with a half-life of 14-99 h depending on the actual weather conditions.…”

Accumulation of Elsinochrome Phytotoxin does not Correlate with Fungal Virulence among Elsinoë fawcettii Isolates in Florida

“…The concentration of elsinochromes was determined by reference to a regression line that was established using pure cercosporin (Sigma, St Louis, MO, USA) as a standard, because no pure elsinochromes are commercially available. Cercosporin and elsinochromes have similar structures, molecular weights and absorbance spectra (Weiss et al., 1987; Ahonsi et al., 2006). Quantitative analysis of the elsinochromes was performed by extracting agar plugs containing fungal hyphae with 5 m KOH and by measuring absorbance at 480 nm.…”