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

Abstract

Biological control as an alternative to chemical pesticides is of increasing public interest. However, to ensure safe use of biocontrol methods, strategies to assess the possible risks need to be developed. The production of toxic metabolites is an aspect which has so far largely been neglected in the risk assessment and the registration process for biocontrol products. We have evaluated the risks of elsinochrome A (ELA) and leptosphaerodione production by the fungus Stagonospora convolvuli LA39, an effective biocontrol agent used against bindweeds. The toxicity of the two metabolites to bacteria, protozoa, fungi and plants was evaluated in in vitro assays. The most sensitive bacteria and fungi were already affected at 0.01-0.07 microM ELA, whereas plants were far less sensitive. Leptosphaerodione was less toxic than ELA. Subsequently, it was investigated whether ELA is present in the applied biocontrol product or LA39-treated bindweed and crop plants. In plants ELA was never detected and in the biocontrol product the ELA concentration was far too low to have toxic effects even on the most sensitive organisms. We conclude that the production of ELA by biocontrol strain LA39 does not pose a risk to the environment or to the consumer.

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

“…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. 2007).…”

“…The fate of Stagonospora convolvuli LA39 (Pfirter and Défago 1998) was investigated in two experiments conducted in areas with natural field and hedge bindweed infestation. A detailed description of cultivation and application of LA39 was provided in a previous study (Boss et al. 2007).…”

Tissue specific reactions of sorghum roots to the mycoherbicideFusariumoxysporumf. sp.strigaeversus the pathogenicF. proliferatum

“…Greenhouse experiments have revealed that Foxy 2 is effective and specific to S. hermonthica causing a reduction in Striga germination of up to 83% (Elzein and Kroschel 2004). To ensure the safe use of biocontrol methods, strategies to assess the associated risks need to be developed (Boss, Maurhofer, Schläpfer, and Defago 2007). For this, it is necessary first of all to understand the interactions between the biocontrol agent and the parasitic weed together with the host plant which is the non-target plant and the desired crop (Hearne 2009); before its implementation on large scale can be recommended.…”

Safety assessment of biocontrol and plant growth-promoting pseudomonads useful in crop production

“…Another factor complicating safety assessments of microbes for novel uses is the current lack of standardised test systems suitable for testing toxicity or pathogenicity of microorganisms with all their constituents and metabolites. Where specific metabolites of potential concern are known, toxicity studies can be performed with these compounds in pure form (Peltola et al , 2004; Boss et al , 2007). However, screening for toxic compounds without prior knowledge of the metabolites produced by a certain microbe requires that the tests be performed on the microbial cells themselves or cell homogenates.…”