Abstract
Pathogenic infestations are significant threats to vegetable yield, and have become an urgent problem to be solved. Rhizoctonia solani is one of the worst fungi affecting tomato crops, reducing yield in some regions. It is a known fact that plants have their own defense against such infestations; however, it is unclear whether any exogenous material can help plants against infestation. Therefore, we performed greenhouse experiments to evaluate the impacts of R. solani on 15- and 30-day old tomato plants after fungal infestation, and estimated the antifungal activity of nanoparticles (NPs) against the pathogen. We observed severe pathogenic impacts on the above-ground tissues of tomato plants which would affect plant physiology and crop production. Pathogenic infection reduced total chlorophyll and anthocyanin contents, which subsequently disturbed plant physiology. Further, total phenolic contents (TPC), total flavonoid contents (TFC), and malondialdehyde (MDA) contents were significantly increased in pathogen treatments. Constitutively, enhanced activities were estimated for catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX) in response to reactive oxygen species (ROS)in pathogen-treated plants. Moreover, pathogenesis-related genes, namely, chitinase, plant glutathione S-transferase (GST), phenylalanine ammonia-lyase (PAL1), pathogenesis-related protein (PR12), and pathogenesis-related protein (PR1) were evaluated, with significant differences between treated and control plants. In vitro and greenhouse antifungal activity of silver nanoparticles (Ag NPs), chitosan nanoparticles, and Ag NPs/CHI NPs composites and plant health was studied using transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectrophotometry. We found astonishing results, namely, that Ag and CHI have antifungal activities against R. solani. Overall, plant health was much improved following treatment with Ag NPs/CHI NPs composites. In order to manage R. solani pathogenicity and improve tomato health, Ag/CHI NPs composites could be used infield as well as on commercial levels based on recommendations. However, there is an urgent need to first evaluate whether these NP composites have any secondary impacts on human health or the environment.
Highlights
Rhizoctonia solani (Kuhn) is a ground-dwelling plant pathogenic fungus with a broadspectrum of hosts and global spread, causing plant diseases like collar rot, root rot, damping off, and wire stem [1]
It is a phytopathogen that attacks tomatoes cultivated under greenhouse conditions, causing root and crown rot diseases
FW), was observed regarding NC and C treatments, respectively (Figure 4B). These results indicated that phenolic compounds were produced in high quantities when tomato plants had been exposed to the fungus
Summary
Rhizoctonia solani (Kuhn) is a ground-dwelling plant pathogenic fungus with a broadspectrum of hosts and global spread, causing plant diseases like collar rot, root rot, damping off, and wire stem [1]. R. solani is the smallest fungus known to originate from “damping-off”, and can live in soil without a host for several years. The main reason behind this survival is the formation of sclerotia, a dense pile of toughened fungal mycelia 1–3 mm in diameter including food stocks [3]. Its broad host range and ability to compose sclerotia make this pathogen very challenging to manage. This pathogen causes disease in several important vegetables and crops including corn, tomato, potatoes, cereals, sugar beet and cucumber
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