A team of researchers from the Research Center for Engineering in Chemical Processes and Forest Products (CIEPQPF) and the Center for Functional Ecology (CFE) of the Faculty of Science and Technology of the University of Coimbra (FCTUC) has found a way to recover waste resulting from the processing of walnut fruit, which currently have no use, through the extraction of compounds with “nematicidal” effect, that is, for the control of parasitic nematodes from plants that affect a wide range of economically important species, causing high losses at the level of production (quality and quantity).
These new nematicides of natural origin result from a collaboration initiated about a decade ago by researchers Hermínio de Sousa (Department of Chemical Engineering) and Isabel Abrantes (Department of Life Sciences), with the objective of reusing and valuing residues from the agrifood industry through the extraction of compounds for later use in different purposes and applications.
In this search, the researchers identified two compounds belonging to the group of naphthoquinones, which would prove to be “bionematodicidas” effective in combating parasitic plant nematodes.
Plant-parasitic nematodes, with an emphasis on root gall nematodes (Meloidogyne spp.), Thus designated as inducing gall formation in the root system of several plants, are one of the greatest threats to agricultural production worldwide.
It is estimated that each year these nematodes cause crop losses, worldwide, of around 5%, which constitutes an obstacle to agricultural production.
Naphthoquinones «are peculiar because they are responsible for the intense aroma of the walnut fruit or the tree itself. When analyzing the molecules of naphthoquinones, it was found that they could function as pesticides of natural origin because they have chemical similarities with commercial molecules.
After optimizing the extraction processes, we obtained an extract enriched in two compounds: 1,4-naphthoquinone and juglone», report Carla Maleita and Mara Braga, researchers in the project.
After analyzing the obtained extract, several tests were followed to verify its effectiveness as a nematodicide. The results were very positive, reveal the researchers from FCTUC: «the active compounds identified in the extract were tested directly on two types of phytoparasitic nematodes that affect tomato and potato crops, root gall nematodes and root lesions. After 72 hours, one of the compounds had eliminated more than 40% of the nematodes, without affecting the non-target organisms and the plants ».
In addition to allowing the recovery of walnut fruit residues, as renewable sources of naphthoquinone-based products, this study also contributes to the development of a more sustainable and environmentally friendly agriculture, constituting an alternative to the application of synthetic nematodicides, which present high impacts on human health and the environment.
The researchers note that “the residues of the walnut fruit, which have some toxicity, are usually placed in landfills which can lead to a high concentration of naphthoquinones in the soil and, eventually, contamination of water courses or groundwater“.
Although it is still necessary to carry out some more laboratory and field tests, the team believes that, in the medium term, these extracts may become part of commercial nematodicidal products «as long as the industry shows interest.
We have several indicators that it is possible to have a product of this nature and with this nematodicidal capacity on the market, since the extracts developed have proved to be an effective alternative to synthetic nematodicides», conclude Carla Maleita and Mara Braga.