Control of postharvest fungal diseases in fruits using external application of RNAi

Polygalacturonase-inhibiting proteins as an exogenously applied natural solution for prevention of postharvest fungal infections

Polygalacturonase inhibiting proteins (PGIPs) are plant proteins involved in the inhibition of polygalacturonases (PGs), cell-wall degrading enzymes often secreted by phytopathogenic fungi. Previously, we confirmed that PGIP2 from Phaseolus vulgaris (PvPGIP2) can inhibit the growth of Aspergillus niger and Botrytis cinerea on agar plate. In this study, we further validated the feasibility of using PGIP as an environmental and ecological friendly agent to prevent fungal infection post-harvest. We found that application of either purified PGIP (full length PvPGIP2 or truncated tPvPGIP2_5-8), or PGIP-secreting Saccharomyces cerevisiae strains can effectively inhibit fungal growth and necrotic lesions on tobacco leaf. We also examined the effective amount and thermostability of PGIP when applied on plants. A concentration of 0.75 mg/mL or higher can significantly reduce the area of B. cinerea lesions. The activity of full-length PvPGIPs is not affected after incubation at various temperatures ranging from -20 to 42 °C for 24 h, while truncated tPvPGIP2_5-8 lost some efficacy after incubation at 42 °C. Furthermore, we have also examined the efficacy of PGIP on tomato fruit. When the purified PvPGIP2 proteins were applied to tomato fruit inoculated with B. cinerea at a concentration of roughly 1.0 mg/mL, disease incidence and area of disease had reduced by more than half compared to the controls without PGIP treatment. This study explores the potential of PGIPs as exogenously applied, eco-friendly fungal control agents on fruit and vegetables post-harvest.

Formulation of essential oils-loaded solid lipid nanoparticles-based chitosan/PVA hydrogels to control the growth of Botrytis cinerea and Penicillium expansum

Botrytis cinerea and Penicillium expansum are phytopathogenic fungi that produce the deterioration of fruits. Thus, essential oil (EO) has emerged as a sustainable strategy to minimize the use of synthetic fungicides, but their volatility and scarce solubility restrict their application. This study proposes the EO of Oreganum vulgare and Thymus vulgaris-loaded solid lipid nanoparticles (SLN) based chitosan/PVA hydrogels to reduce the infestation of fungi phytopathogen. EO of O. vulgare and T. vulgaris-loaded SLN had a good homogeneity (0.21-0.35) and stability (-28.8 to -33.0 mV) with a mean size of 180.4-188.4 nm. The optimization of EO-loaded SLN showed that the encapsulation of 800 and 1200 μL L-1 of EO of O vulgare and T. vulgaris had the best particle size. EO-loaded SLN significantly reduced the mycelial growth and spore germination of both fungi pathogen. EO-loaded SLN into hydrogels showed appropriate physicochemical characteristics to apply under environmental conditions. Furthermore, rheological analyses evidenced that hydrogels had solid-like characteristics and elastic behavior. EO-loaded SLN-based hydrogels inhibited the spore germination in B. cinerea (80.9 %) and P. expansum (55.7 %). These results show that SLN and hydrogels are eco-friendly strategies for applying EO with antifungal activity.

Physical properties of zein-alginate-glycerol edible films and their application in the preservation of chili peppers (Capsicum annuum L.)

Edible films elaborated from macromolecules, like carbohydrates, proteins, and lipids, must protect and maintain the integrity of foods during their handling, storage, and transportation. In this work, the effect of the concentration of zein (1-2% w/v), sodium alginate (1.5-2% w/v), and glycerol (2-4% w/v) on edible films physicochemical properties was evaluated. The Zein-Alginate-Glycerol interaction was evidenced by the FTIR analysis, the high permeability to water vapor and contact angles less than 90° of the polymer matrices formed. The film made with 2% zein, 1.5% sodium alginate and 4% glycerol preserved the quality of the chili pepper during 15 days of storage at 20 °C, the edible films allowed 3 more days of shelf life for weight loss and 10 more days for firmness. Edible films could be used in chili peppers that are destined for industrial processing, and before use, remove the film with a simple wash.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01393-z.

Microbial Biofungicides as a Substitute for Chemical Fungicides in the Control of Phytopathogens: Current Perspectives and Research Directions

These days, two important issues are causing concern in the global community: the alarmingly growing trend of the human population and the issue of food security. To this end, people around the world have been searching for solutions that could feed the needy in a sustainable way. In response to this urgent call, scientists from around the world started working on increasing crop production and productivity by controlling crop pathogens that could harm the productivity of crops. Synthetic fungicides have been in use for controlling crop diseases for several decades, but later, due to the evidenced side effects of the fungicides, there have been attempts to shift towards a less cost-effective and eco-friendly method of controlling crop diseases, and so far, many remarkable results have been achieved. However, due to the less effective and shorter shelf life of microbial biofungicides, as well as the less accessibility of these microbial biofungicides to growers around the world, it became difficult to remove the fungicides totally from the market. To minimize this problem, researchers suggested an integrated approach: the combination of microbial biofungicides with a reduced dose of synthetic fungicides. Hence, this review explored the status as well as the merits and demerits of microbial biofungicides as compared to synthetic fungicides.

Identification of bioactive compounds of Bacillus velezensis HNA3 that contribute to its dual effects as plant growth promoter and biocontrol against post-harvested fungi

IMPORTANCE

The current study is an extension to our previous work on the plant growth-promoting rhizobacteria (PGPR) Bacillus velezensis HNA3 strain, which comes to confirm and reveals the huge stock of active secondary metabolites produced by HNA3. HNA3-emitted volatile organic compounds (VOCs) have demonstrated the capacity to impede the growth of phytopathogens affecting some fruits and vegetables, even in the absence of direct contact. Additionally, these volatiles enhanced soybean seed germination by breaking seed dormancy and inducing root system development. Furthermore, they promoted seedling growth, giving it prominence in soybean cultivation. The relevance of active volatiles derives from the fact that they can be developed as natural-safe biocontrol agents and plant promoters. This research validates the remarkable bioactivities exhibited by the Bacillus velezensis HNA3 and their potential applications in agriculture as an inoculant, encompassing biocontrol, plant growth promotion, and seed germination activities, thereby offering a safer alternative to hazardous chemicals.

Research progress on the application of different preservation methods for controlling fungi and toxins in fruit and vegetable

Fruits and vegetables are susceptible to fungal infections during picking, transportation, storage and processing, which have a high potential to produce toxins. Fungi and toxins can cause acute or chronic poisoning after entering the body. In the field of fruit and vegetable preservation, technologies such as temperature control, modified atmosphere, irradiation, application of natural or chemical preservatives, and edible films are commonly used. In practical applications, according to the types, physiological differences and actual needs of fruits and vegetables, suitable preservation methods can be selected to achieve the effect of preservation and control of fungi and toxins. The starting point of fresh-keeping technology is to delay post-harvest senescence of fruits and vegetables, inhibit the respiratory intensity, and control the reproduction of microorganisms, which is important to control the reproduction of fungi and the production of toxins. From the three directions of physical, chemical and biological means, the article analyses and explores the effects of different external factors on the production of toxins and the effects of different preservation techniques on fungal growth and toxin production in fruits and vegetables, in order to provide new ideas for the preservation of fruits and vegetables and the control of harmful substances in food.

Management of Post-Harvest Anthracnose: Current Approaches and Future Perspectives

Anthracnose is a severe disease caused by Colletotrichum spp. on several crop species. Fungal infections can occur both in the field and at the post-harvest stage causing severe lesions on fruits and economic losses. Physical treatments and synthetic fungicides have traditionally been the preferred means to control anthracnose adverse effects; however, the urgent need to decrease the use of toxic chemicals led to the investigation of innovative and sustainable protection techniques. Evidence for the efficacy of biological agents and vegetal derivates has been reported; however, their introduction into actual crop protection strategies requires the solutions of several critical issues. Biotechnology-based approaches have also been explored, revealing the opportunity to develop innovative and safe methods for anthracnose management through genome editing and RNA interference technologies. Nevertheless, besides the number of advantages related to their use, e.g., the putative absence of adverse effects due to their high specificity, a number of aspects remain to be clarified to enable their introduction into Integrated Pest Management (IPM) protocols against Colletotrichum spp. disease.

Discovery of Chitin Deacetylase Inhibitors through Structure-Based Virtual Screening and Biological Assays

Chitin deacetylase (CDA) inhibitors were developed as novel antifungal agents because CDA participates in critical fungal physiological and metabolic processes and increases virulence in soilborne fungal pathogens. However, few CDA inhibitors have been reported. In this study, 150 candidate CDA inhibitors were selected from the commercial Chemdiv compound library through structure-based virtual screening. The top-ranked 25 compounds were further evaluated for biological activity. The compound J075-4187 had an IC50 of 4.24 ± 0.16 μM for AnCDA. Molecular docking calculations predicted that compound J075-4187 binds to the amino acid residues, including active sites (H101, D48). Furthermore, compound J075-4187 inhibited food spoilage fungi and plant pathogenic fungi, with minimum inhibitory concentration (MIC) at 260 μg/ml and minimum fungicidal concentration (MFC) at 520 μg/ml. Therefore, compound J075-4187 is a good candidate for use in developing antifungal agents for fungi control.