Pathogenic susceptibility in microplastic-exposed crops: the case of Solanum lycopersicum var San Marzano nano

Beatrice Chiavacci ¹, Ivan Baccelli ², Sihem Fodil ², Cristina Gonnelli ¹, Ilaria Colzi ¹

Department of Biology, University of Florence, Florence, Italy ¹, Institute for Sustainable Plant Protection, National Research Council, Sesto Fiorentino, Italy ²

Plastic has become a pervasive presence in our daily life; used in all industrial sectors and commercialized in the most diverse forms, its production rates are growing year by year. Due to this, the dispersion of this material in the environment becomes inevitable and its exposure to physical, chemical and biological processes leads to micro- and nano-plastics formation (MPs, particles diameter < 5 mm and ≤ 100 nm, respectively). The harmfulness of these polymers depends on the particle size with the smaller as the more toxic. Despite the recent increasing attention on the fate of MPs in the soil-plant system, the effect that their accumulation in the soil generates on disease resistance mechanisms of plants has never been investigated. Since agriculture is moving towards sustainability targets, it appears impelling to understand how soil pollution with MPs may affect the plant innate immune system. Enhanced pathogen susceptibility, for instance, would have consequences in terms of crop losses and increased use of plant protection products. The project “MINACROP - The dark side of MIcro- and NAno-plastics in the soil: impact on CROP physiology and pathogen resistance” (PRIN2022) aims at filling this gap by investigating at the physiological and phyto-pathological level the effects of MPs on the model crop species Solanum lycopersicum var. San Marzano Nano. To address this issue, two of the most widely dispersed plastic polymers in the environment and in agricultural soils, polyvinyl chloride (PVC) and polyethylene terephthalate (PET), were chosen, based on the ecologically realistic MPs levels found in these areas. Plant seedlings were exposed to three different MPs concentrations (0.5, 1.0 and 1.5 % w/w , size range 40-50 μm) and grown in pots for 14 days under controlled conditions. At the end of the treatment period, before harvesting, photosynthetic efficiency and pigment content analysis were performed. Then, plants were sampled and biometric traits and elemental composition were evaluated. The effects of MPs contamination on the susceptibility of S. lycopersicum to two different pathogens (Botrytis cinerea and Pseudomonas syringae pv tomato DC3000) were evaluated after infection. MPs-exposed plants showed a higher fresh and dry weight, even though not significantly. Photosynthetic efficiency was not considerably altered after 14 days, except for the minimal chlorophyll fluorescence parameter, consistently with a relevant MPs dose-dependent reduction of chlorophyll and flavonoid levels observed in all the plastic treatments. Despite the short exposure period, all MPs concentrations impacted on the ionomic profile of plant shoots. Interestingly, plants treated with higher MPs concentrations exhibited a significant increased P. syringae cell growth in infected leaves, while B. cinerea induced larger lesion diameter only in PET treated samples. The obtained results indicate that soil contamination with MPs has negative impacts on the disease resistance against S. lycopersicum pathogens. Despite the lack of detectable adverse effects on plant growth, the alterations that MPs induced in the plant physiology resulted in a higher susceptibility to pathogens infections which may have a negative impact on tomato crop health, productivity and quality.

Main author career stage: Postdoc / Fellow

Contribution type: Talk

First choice session: 4. Structure, physiology, and development

Second choice session: 2. Ecology