Abstract
Research has been increasingly focusing on the selection of novel and effective biological control agents (BCAs) against soil-borne plant pathogens. The large-scale application of BCAs requires fast and robust screening methods for the evaluation of the efficacy of high numbers of candidates. In this context, the digital technologies can be applied not only for early disease detection but also for rapid performance analyses of BCAs. The present study investigates the ability of different Trichoderma spp. to contain the development of main baby-leaf vegetable pathogens and applies functional plant imaging to select the best performing antagonists against multiple pathosystems. Specifically, sixteen different Trichoderma spp. strains were characterized both in vivo and in vitro for their ability to contain R. solani, S. sclerotiorum and S. rolfsii development. All Trichoderma spp. showed, in vitro significant radial growth inhibition of the target phytopathogens. Furthermore, biocontrol trials were performed on wild rocket, green and red baby lettuces infected, respectively, with R. solani, S. sclerotiorum and S. rolfsii. The plant status was monitored by using hyperspectral imaging. Two strains, Tl35 and Ta56, belonging to T. longibrachiatum and T. atroviride species, significantly reduced disease incidence and severity (DI and DSI) in the three pathosystems. Vegetation indices, calculated on the hyperspectral data extracted from the images of plant-Trichoderma-pathogen interaction, proved to be suitable to refer about the plant health status. Four of them (OSAVI, SAVI, TSAVI and TVI) were found informative for all the pathosystems analyzed, resulting closely correlated to DSI according to significant changes in the spectral signatures among health, infected and bio-protected plants. Findings clearly indicate the possibility to promote sustainable disease management of crops by applying digital plant imaging as large-scale screening method of BCAs' effectiveness and precision biological control support.
Highlights
Baby leaf vegetables constitute the major ingredient of readyto-eat salads, very appreciated worldwide by consumers looking for healthy diets rich in fibers and low in calories, with organoleptic and nutraceutical traits enhanced in pigmented varieties
Findings of the present study indicate the potential to boost the sustainability of disease management protocols trough highperforming hyperspectral vegetation indices (VIs) that can drive the biocontrol practices, such as, for example, the microbial augmentation, based on the early recognition of the worsening of the plant state and of the possible effectiveness reduction of the adopted plant protection strategy
The high-effective Trichoderma strains identified in this study are able for protecting baby-leaf vegetables from a wide-spectrum of soil-borne pathogens, such as R. solani, S. sclerotiorum, and R. rolfsii
Summary
Baby leaf vegetables constitute the major ingredient of readyto-eat salads, very appreciated worldwide by consumers looking for healthy diets rich in fibers and low in calories, with organoleptic and nutraceutical traits enhanced in pigmented varieties. The soil-borne fungi Rhizoctonia solani Kuhn, Sclerotinia sclerotiorum (Lib.) de Bary and Sclerotium rolfsii Sacc., belonging to the Phylum Basidiomycota, are parenchymatic, polyphagous, necrotrophic pathogens of different salad crops, causing huge economic losses and symptoms ranging from the simple rotting of the attacked organs to the damping-off. Their non-chemical counteraction is requested under sustainable management systems pursuing the zero residues goal, while it is mandatory according to the organic farming rules (Giménez et al, 2019). The integrated disease management people are exploring alternative approaches to synthetic fungicides, including the implementation of effective microbes able to control phytopathogenic attacks, referred as biological control agents (BCAs)
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