Herbicidal properties of the commercial formulation of methyl cinnamate, a natural compound in the invasive silver wattle (Acacia dealbata)

Abstract

Plants that release molecules affecting other plants are a source of potential bioherbicides. Silver wattle (Acacia dealbata Link), considered invasive worldwide, was found to be phytotoxic to various other plant species. Combining the search for alternative bioherbicides while reducing the spread of this invader by preventing seed formation is a good potential strategy to solve both agricultural and environmental problems. This study aimed to identify nonvolatile compounds from A. dealbata flowers and explore their phytotoxicity on the germination process and seedling and plant growth of lettuce (Lactuca sativa L.), wheat (Triticum aestivum L.), and rigid ryegrass (Lolium rigidum Gaudin). We identified methyl cinnamate and methyl anisate as potential phytotoxins in the extracts, but we used pure commercial molecules to conduct bioassays. Methyl cinnamate showed higher phytotoxicity than methyl anisate and was selected for further bioassays. Methyl cinnamate reduced guaiacol peroxidase activity by 57% and 85% in L. rigidum and lettuce, respectively, and α-amylase by 6% in L. rigidum. This compound also inhibited early stem and radicle growth of dicotyledonous lettuce (60% and 89%, respectively) and monocotyledonous L. rigidum (76% and 87%, respectively), both species having small seeds. However, wheat with a larger seed size was not affected by the phytotoxin. The results obtained indicate a potential bioherbicidal effect for methyl cinnamate, and its application might be useful in wheat crops infested by L. rigidum. We suggest that collecting A. dealbata flowers would prevent Acacia seed formation and thus play a role in invasive pest management, as well as serving as a source of potential herbicides to other species.

Potential role of Eucalyptus spp. and Acacia spp. allelochemicals in weed management

“…Methyl cinnamate is a compound found in the flowers of A. dealbata and other plants (Khanh et al, 2008) and has shown its herbicidal effects on Lolium rigidum Gaudin with its application reducing guaiacol peroxidase activity up to 57% and also inhibiting early stem and radicle growth of L. rigidum by 76% and 87%, respectively (Lorenzo et al, 2020). Methyl cinnamate can also significantly reduce L. rigidum seed germination and root length when applied at 640 nL cm -3 (Vasilakoglou et al, 2013).…”

Insights for the Valorization of Biomass from Portuguese Invasive Acacia spp. in a Biorefinery Perspective

“…The authors found methyl cinnamate as the most active compound, which showed selective phytotoxicity by inhibiting early stem and radicle growth of dicotyledonous lettuce (60% and 89%, respectively) and monocotyledonous L. rigidum (76% and 87%, respectively), but not affecting wheat. These results encouraged the exploitation of A. dealbata flowers as a source of potential bioherbicides, namely to be applied in wheat crops infested by rigid ryegrass [19]. A water extract from A. melanoxylon leaves evidenced promising results as a potential bioherbicide agent, given the inhibitory effect on the growth of Galician native species [64].…”

“…can be of great economic importance, since they are important sources of essences for the cosmetic and perfume industries and are of valuable anthochlor pigments (chalcones), in addition to relevant biological activities that have been found in their extracts. Moreover, its exploitation can be of crucial importance to the control of the propagation of Acacia spp., once its collection during the flowering period prevents the formation of seeds, so hindering plant proliferation through the seed dispersal route [19]. The biological activities and uses of Acacia spp.…”

“…Anisal is widely used in flavor and fragrance indutries, methyl p-hydroxycinnamate previously showed anti-inflammatory activity [99], and nematicidal effects were associated with p-anysil alcohol [100]. Lorenzo et al [19] explored the potential herbicidal effect of two compounds present in flowers of A. dealbata, methyl cinnamate and methyl anisate, against well-established plants, namely lettuce (L. sativa), the widely consumed wheat crop (Triticum aestivum), and against rigid ryegrass (Lolium rigidum Gaudin), a common weed in winter cereal and wheat crops. The authors found methyl cinnamate as the most active compound, which showed selective phytotoxicity by inhibiting early stem and radicle growth of dicotyledonous lettuce (60% and 89%, respectively) and monocotyledonous L. rigidum (76% and 87%, respectively), but not affecting wheat.…”

“…[18] In this way, the production of bioactive preparations of Acacia spp., either from well-established areas or from the biomass generated in the control operations, can be an option to bring an important economic return, overcoming expenses with collection and transport, while simultaneously contributing to motivating forest cleaning and management actions, reducing the risk of fires and improving the social-economic development of rural areas. Moreover, the valorization of its flowers, as an example, will have a positive contribution to the control of the proliferation by preventing the formation of seeds, thus minimizing the spread through the seed dispersal route [19]. Other well-studied applications of Acacia spp.…”