Abstract
Phoma-like fungi are known as producers of diverse spectrum of secondary metabolites, including phytotoxins. Our bioassays had shown that extracts of Paraphoma sp. VIZR 1.46, a pathogen of Cirsium arvense, are phytotoxic. In this study, two phytotoxically active metabolites were isolated from Paraphoma sp. VIZR 1.46 liquid and solid cultures and identified as curvulin and phaeosphaeride A, respectively. The latter is reported also for the first time as a fungal phytotoxic product with potential herbicidal activity. Both metabolites were assayed for phytotoxic, antimicrobial and zootoxic activities. Curvulin and phaeosphaeride A were tested on weedy and agrarian plants, fungi, Gram-positive and Gram-negative bacteria, and on paramecia. Curvulin was shown to be weakly phytotoxic, while phaeosphaeride A caused severe necrotic lesions on all the tested plants. To evaluate phaeosphaeride A’s herbicidal efficacy, the phytotoxic activity of this compound in combination with five different adjuvants was studied. Hasten at 0.1% (v/v) was found to be the most potent and compatible adjuvant, and its combination with 0.5% (v/v) semi-purified extract of Paraphoma sp. VIZR 1.46 solid culture exhibited maximum damage to C. arvense plants. These findings may offer significant importance for further investigation of herbicidal potential of phaeosphaeride A and possibly in devising new herbicide of natural origin.
Highlights
The search of new biologically active compounds and investigation of their mode of action is an important task for the development of new pesticides, including herbicides [1,2]
The phylogenetic tree of large subunit (LSU) was used for species of closely related genera to assess the placement of the isolates within the family Phaeosphaeriaceae [22]
Curvulin and phaeosphaeride A were isolated for the first time as phytotoxic metabolites from
Summary
The search of new biologically active compounds and investigation of their mode of action is an important task for the development of new pesticides, including herbicides [1,2]. Phytotoxins of Phoma macrostoma, macrocidin A and macrocidin B were found to be active ingredients of the extracts obtained from liquid culture of this fungus which are used as a bioherbicide for Canada thistle [10]. The most of natural phytotoxins cannot overcome the cuticle barrier of the plant leaves and in many cases leaf wounding or infiltration are used to obtain a phytotoxic effect in currently used bioassays [17]. There is no data available on the use of adjuvants together with natural phytotoxins to improve their activity on intact leaves of weeds. The effect of five commercial adjuvants was studied in order to evaluate the herbicidal potential of one of the main phytotoxins produced by Paraphoma sp.
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