Lignin–Chitosan Nanocarriers for the Delivery of Bioactive Natural Products against Wood-Decay Phytopathogens

Abstract

The use of nanocarriers (NCs), i.e., nanomaterials capable of encapsulating drugs and releasing them selectively, is an emerging field in agriculture. In this study, the synthesis, characterization, and in vitro and in vivo testing of biodegradable NCs loaded with natural bioactive products was investigated for the control of certain phytopathogens responsible for wood degradation. In particular, NCs based on methacrylated lignin and chitosan oligomers, loaded with extracts from Rubia tinctorum, Silybum marianum, Equisetum arvense, and Urtica dioica, were first assayed in vitro against Neofusicoccum parvum, an aggressive fungus that causes cankers and diebacks in numerous woody hosts around the world. The in vitro antimicrobial activity of the most effective treatment was further explored against another fungal pathogen and two bacteria related to trunk diseases: Diplodia seriata, Xylophilus ampelinus, and Pseudomonas syringae pv. syringae, respectively. Subsequently, it was evaluated in field conditions, in which it was applied by endotherapy for the control of grapevine trunk diseases. In the in vitro mycelial growth inhibition tests, the NCs loaded with R. tinctorum resulted in EC90 concentrations of 65.8 and 91.0 μg·mL−1 against N. parvum and D. seriata, respectively. Concerning their antibacterial activity, a minimum inhibitory concentration of 37.5 μg·mL−1 was obtained for this treatment against both phytopathogens. Upon application via endotherapy on 20-year-old grapevines with clear esca and Botryosphaeria decay symptoms, no phytotoxicity effects were observed (according to SPAD and chlorophyll fluorescence measurements) and the sugar content of the grape juice was not affected either. Nonetheless, the treatment led to a noticeable decrease in foliar symptoms as well as a higher yield in the treated arms as compared to the control arms (3177 vs. 1932 g/arm), suggestive of high efficacy. Given the advantages in terms of controlled release and antimicrobial product savings, these biodegradable NCs loaded with natural extracts may deserve further research in large-scale field tests.

The Practical Utility of Imidazolium Hydrogen Sulfate Ionic Liquid in Fabrication of Lignin-Based Spheres: Structure Characteristic and Antibacterial Activity

“…Lignin- or cellulose-based micro- and nanomaterials capable of encapsulating active substances have been of great interest to scientists in recent times. These nanocarriers may be loaded by medicines (e.g., antibiotics), natural bioactive products (e.g., extracts from medicinal plants), porphyrins, silver ions or metal oxides ( Bazant et al, 2014 ; Klapiszewski et al, 2015 ; Li et al, 2020 ; Maldonado-Carmona et al, 2020 ; Paudel et al, 2021 ; Sánchez-Hernández et al, 2022 ). This allows to obtain antimicrobial activity of such materials.…”

“…Finally, the particles were prepared with a core-shell morphology and great antibacterial activity. Sánchez-Hernández et al (2022 ) produced lignin-chitosan-based nanoparticles which were loaded with natural bioactive products and they were tested against Diplodia seriata , Xylophilus ampelinus , and Pseudomonas syringae pv. syringae and the antibacterial activity was observed with good efficiency.…”

Sustainable Management of Diseases in Horticulture: Conventional and New Options

“…These nanocarriers can release the active product selectively to the plant. Among these nanocarriers, chitosan oligomers and methacrylated lignin could be effectively utilised [119]. PGPR strains could also be utilised as nano-fertilisers and/or inducers of systemic resistance to phytopathogens [120].…”

“…Endotherapy performed with glutaraldehyde on grapevine cuttings provided a satisfactory control of Phaeoacremonium minimum, one of the fungi involved in the esca disease complex [136]. In addition, endotherapy performed on grapevine plants showing symptoms of esca disease complex using chitosan oligomers as nanocarriers loaded with the extracts of some plants offering antimicrobial properties, such as Rubia tinctorum, Equisetum arvensis, Urtica dioica, and Silybum marianum, yielded a significant reduction of foliar symptoms [119].…”

Antifungal Activity of Methylxanthines against Grapevine Trunk Diseases

“…Firstly, the study presented herein fulfills a screening purpose, designed to shortlist-based on in vitro results-those treatments that may be the most effective for the control of GTDs. Nonetheless, in vivo and field (multi-year and multi-location) studies will be needed to confirm the real-world applicability of these treatments, define appropriate dosages, and determine the most suitable application procedure (e.g., via fertigation or endotherapy using nanocarriers [32]).…”