The objective of the proposal is to develop a strategy for controlling fungal diseases in crop plants based on the use of biopolymeric nanoparticles (NPs) loaded with agrochemicals. The effect of biopolymeric NPs on plant growth and metabolism will be investigated to ensure the phyto-safety of this innovative approach.
The proposal will focus on a highly remunerative fresh-market variety of tomato variety datterino F1 zucchero and on one of its fungal pathogen, i.e. Botrytis cinerea, causal agent of the grey mold disease chosen within a list of the most problematic microorganisms for the tomato agro-industry. The agrochemical fluopyram, specifically used to limit this pathogen, will be used as free or loaded in poly(lactic-co-glycolic acid)(PLGA) NPs.
A rapid screening (multiwell plate assays) will be settled for identifying the best performing size and amount of NPs and agrochemical to be used. The investigation will be performed on tomato plants under controlled conditions in detached leaves and potted plants. The influence of empty or fluopyram-loaded PLGA NPs and of free fluopyram on B. cinerea infected and not infected plants will be evaluated by morphological and phenomenological observations. Furthermore, the primary and secondary metabolism of tomato leaves will be investigated by NMR-based metabolomics and LC-MS-based lipidomics. The study will allow to identify the best option for controlling B. cinerea that will be sustainable for tomato (no phytotoxicity) whilst consistently reducing the amount of agrochemicals used.
Nanotechnologies are gaining attention for having an enormous impact on all human activities, including agriculture, even if the production of some nanomaterials is not environmentally friendly or could have adverse effects on agriculture and the environment (Vurro et al. 2019 Pest Manag Sci DOI 10.1002/ps.5348. Other nanomaterials could allow the development of nanoformulated pesticides which could administered in smaller quantities and with lower frequency, making them more effective and more sustainable. Nanoformulations can improve efficacy, reduce effective doses, and increase shelf-life and persistence of bioactives. Polymer nanoparticles and nanocapsules are composed of natural or synthetic polymeric materials, some of which have desirable features such as biodegradability. (Gogos et al. 2012 JAFC 60:9781). The idea of using nanomaterials for field applications in agriculture must be addressed carefully in order to avoid the creation of new problems while solving others (Perez-de-Luque A. 2017 Front Environ Sci 5:12). Several polymers such as chitosan, poly(lactic-co-glycolic acid) (PLGA), poly(epsilon-caprolactone) (PCL), and zein have shown great potential for use in the development of nano-based delivery systems for plants ( Palocci et al. 2017 Plant Cell Reports 36: 1917).
Effective pest management is a major challenge in modern agriculture, with a need to consider control efficacy, cost affordability, environmental safety, toxicity towards non-target organisms, and sustainability of the production system. Despite remarkable progress in many technological fields, most management of these constraints is still based on the use of synthetic chemicals. However, a large number of pesticides have already been withdrawn for regulatory reasons, because of their hazardous effects on the ecosystem or on the food chain, or because they have become ineffective as the result of increasing pesticide resistance (Kah M. et al. 2018 Nat Nanotechnol 13: 677). For those reasons, determination of the toxicity and potential negative environmental impacts of nanodevices is necessary before approval. One of the best ways to deal with this obstacle is to turn to nanomaterials that have proven to be innocuous and safe for human consumption.
However, this is not always a guarantee that massive application in the field of a product already in use in the food industry will not have negative environmental effects, as is the case with silver NPs. Toxicity is a relevant factor to be tested before using a nanodevice in agricultural applications. The direct toxic effects of NPs are usually associated with their chemical composition and their high specific surface area (high reactivity), which makes them biologically reactive. However, it is important to differentiate between compounds that produce cytotoxicity and those that are toxic for the entire organism (acute or chronic). Because of their high reactivity, some nanomaterials can be occasionally cytotoxic and lethal for individual cells, but their effect on the entire organism is negligible and innocuous. Nanomaterials can have damaging effects on plants and other organisms, or can affect environmental processes. In the case of plants the negative consequences can involve alterations in photosynthesis due to several factors such as reduction in light availability and gas exchange, leading to decreased CO2 fixation, or by directly inactivating the plant photosystem and affecting the electron transport chain. Additionally, plant growth and physiology can be negatively altered [Lin and Xing (2007). Environ. Pollut. 150:243].
Our proposal will guarantee a consistent step beyond the state of the art in understanding and evaluating from phenotype to metabolomic level the impact of the use of NPs in crop plants. Moreover, this proposal, conceived as a proof-of-concept, would pave the way for a novel approach in plant pathogens control. As previously said, agrochemical companies are facing a growing number of constraints from the emergence of pathogen resistance as well as from more and more severe legislation. The use of NPs could provide an effective strategy for lowering the doses of fungicides significantly delaying the appearance of resistance at field level and gaining to researchers more time for individuating more sustainable solutions for challenging pathogens whilst guaranteeing the productivity and safety of plant products.