Abstract
The use of many fungal phytotoxins as natural herbicides is still limited because they cannot penetrate leaf cuticle without injury and a little is known on their selectivity. In order to assess the herbicidal potential of phytotoxic 10-membered lactones (stagonolide A, stagonolide K, and herbarumin I), the selection of adjuvants, the evaluation of selectivity of the toxins and the efficacy of their formulations were performed. Among four adjuvants tested, Hasten™ (0.1%, v/v) increased phytotoxic activity of all the toxins assayed on non-punctured leaf discs of Sonchus arvensis. When assayed on intact leaf fragments of 18 plants species, 10 species were low to moderately sensitive to stagonolide A, while just five and three species were sensitive to stagonolide K and herbarumin I, respectively. Both leaf damage or addition of Hasten™ (0.1%) to the formulations of the compounds considerably increased or altered the sensitivity of plants to the toxins. Stagonolide A was shown to be non-selective phytotoxin. The selectivity profile of stagonolide K and herbarumin I depended on the leaf wounding or the adjuvant addition. Stagonolide A and herbarumin I formulated in 0.5% Hasten™ showed considerable herbicidal effect on S. arvensis aerial shoots. This study supported the potential of the oil-based adjuvant Hasten™ to increase the herbicidal efficacy of natural phytotoxins.
Highlights
The application of chemical control has aided humanity to increase crop productivity for many years, but over the past few decades the intensive use of synthetic herbicides has led to non-targeted adverse environmental effects, soil and water contamination and herbicide resistance in weeds [1].The bioherbicides and natural product-derived herbicides (NPDH) are considered as relatively safe alternatives for weed control in both organic and conventional agriculture [2,3].Natural phytotoxins of microbial and plant origin have been used as base scaffolds for new NPDHs
Among four adjuvants tested HastenTM was shown to be most compatible with the fungal phytotoxins allowing them to damage the intact leaf discs of
Here, we demonstrated some changes in selectivity of three phytotoxic nonenolides when applied in formulations with 0.1% HastenTM that is important for their future development as NPDHs
Summary
The bioherbicides and natural product-derived herbicides (NPDH) are considered as relatively safe alternatives for weed control in both organic and conventional agriculture [2,3]. Natural phytotoxins of microbial and plant origin have been used as base scaffolds for new NPDHs. Glufosinate (a synthetic mixture of d- and l-phosphinothricin, the latter is a breakdown product of natural phytotoxin bialophos isolated from Streptomyces spp.), manuka oil (from the plant, Leptospermum scoparium) and triketone herbicides Ascaulitoxin and its aglycone, phytotoxic non-proteinogenic amino acids produced by Ascochyta caulina [5], showed the herbicidal potential as reviewed by Cimmino et al, 2015 [6].
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