Search Results (5)

Verticillium spp. are soil-borne fungal pathogens capable of infecting over 400 plant species via their root systems, with each species demonstrating a distinct host range. The primary host of Verticillium nonalfalfae is the hop plant (Humulus lupulus), which becomes affected by Verticillium wilt and, in severe cases, dieback. A dual screening approach was employed to isolate Streptomycetes as potential biocontrol agents from the hop root systems alongside other bacterial species from hop xylem. Three Pseudomonas strains from the xylem and three Streptomyces strains from the roots were selected based on their in vitro antifungal activity against Verticillium dahliae and/or V. nonalfalfae. Their potential for controlling Verticillium wilt was further assessed through in planta assays conducted under greenhouse conditions. The results demonstrated that Pseudomonas sp. HX1, Streptomyces luteogriseus HR40, and Streptomyces flavofungini HR77 significantly reduced the disease severity index by 32.56% compared to artificially infected control plants. In contrast, the commercial biocontrol product Serenade^® ASO, containing Bacillus amyloliquefaciens QST 713, achieved a reduction of 13.96%. These findings underscore the potential of the selected bacterial strains as promising candidates for the biological control of Verticillium wilt in hops affected by V. nonalfalfae. Full article

Brown rot disease caused by Monilinia fructicola is one of the most important peach fruit threats in the world. The use of biological control agents (BCAs), instead of synthetic fungicides, to successfully inhibit postharvest disease development is a challenge in sustainable and efficient crop management. The commercially available BCA Bacillus amyloliquefaciens QST 713 (formerly Bacillus subtilis QST713) is able to inhibit a variety of fungal pathogens and suppress several plant diseases. Our results showed that this BCA inhibited mycelial growth in vitro, and was able to suppress the disease’s severity in peach fruits via delaying and reducing brown rot symptoms. A transcriptomic analysis of fruits during their pre-treatment with this biocontrol agent following M. fructicola challenge revealed a significant upregulation of specific differentially expressed genes (DEGs) at 48 h after inoculation (HAI). These genes are related to the activation of several transcriptional factors, such as members of the WRKY and NAC families, and receptors that are involved in pathogen recognition and signaling transduction (e.g., LRR-RLKs). Furthermore, the inhibition of M. fructicola by this biocontrol agent was confirmed by analyzing the expression profiles of specific fungal genes, which highlighted the direct antimicrobial impact of this bacterial strain against the fungus. Hence, these findings clearly suggest that B. amyloliquefaciens QST 713 is an efficient BCA against brown rot disease, which can directly inhibit M. fructicola and improve peach fruit tolerance. Full article

As climate change is an imminent threat to the environment and agriculture, there is an increasing need to find immediate solutions capable of compensating for water deficits even in semi-arid conditions. This study is focused on the evaluation of the vegetative growth of grapevine plants Vitis vinifera L., of the Greek variety “Debina” in a water deficit environment, with the application of two bacterial-based formulations: one with Bacillus amyloliquefaciens (strain QST 713) and one with Sinorhizobium meliloti (strain cepa B2352). The two formulations were tested under rational irrigation (100% of Available Water) and deficit irrigation (57% of AW). After 140 days, plant growth parameters, such as total plant growth length, leaf area, roots, shoots, and leaves dry biomass showed better performance on treatments with plant growth-promoting rhizobacteria (PGPR) formulations under either rational or deficit irrigation conditions. In addition, the metabolic response of the grapevine plants to the deficit irrigation stress, such as the total chlorophyll, leaf relative water, total phenolic, and proline content, proved to be enriched on the treatments with PGPR formulations during this experiment. The two formulations, in conditions of abiotic stress, achieved to almost compensate for the irrigation deficit, boosting the plant metabolism. This study reveals the need for further research on PGPR biostimulants, as this first trial of these formulations on grapevine could be significant in the case of water scarcity and climate change. Full article

Gnomoniopsis smithogilvyi (Gs) is a relevant pathogen of chestnut since it provokes significant losses worldwide. The aim of this study was to screen the effect of a new biocontrol agent (BCA) against Gs isolated from chestnut (CIMO-BCA1) on the mould’s growth as well as on the production of secondary metabolites. The chemical fungicide Horizon^® (tebuconazole; HOR) and the commercial biofungicide Serenade^® ASO (Bacillus amyloliquefaciens QST 713; ASO) were also tested. Three concentrations of each antifungal (HOR, ASO, and CIMO-BCA1) were faced with Gs in the growth study in a chestnut-based medium. The intermediate concentrations were used for the analyses of metabolites by LC-MS/MS. CIMO-BCA1 was also identified as B. amyloliquefaciens. All agents reduced the mould’s growth, and the CIMO-BCA1 treatment with an intermediate concentration was the most effective. The metabolite analysis revealed, for the first time, the production of two mycotoxins by Gs, including 3-nitropropionic acid and diplodiatoxin. Additionally, HOR stimulated the production of diplodiatoxin. In conclusion, Gs could present a health risk for consumers. B. amyloliquefaciens strains effectively decreased the mould’s growth, but they must be applied at effective concentrations or in combination with other strategies to completely reduce the hazard. Full article

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum, is a devastating disease of oilseed rape that may cause significant yield losses if not controlled by cultural management strategies and fungicide applications. Studies were conducted to evaluate the efficacy of different group of fungicides as well as a biopesticide, including azoxystrobin, boscalid, fludioxonil, prothioconazole, tebuconazole, azoxystrobin/tebuconazole, boscalid/pyraclostrobin, prothioconazole/fluopyram and Bacillus amyloliquefaciens, on baseline sensitivity of S. sclerotiorum isolates under in-vitro conditions as well as control of SSR in the field. Artificial inoculation and mist irrigation prompt to reproducible SSR infection in oilseed rape cultivation. All compounds significantly reduced 36.7% to 86.9% SSR severity and increased 55.2% to 98.7% yield, 1.5% to 7.0% thousand grain-weight, 1.5% to 5.9% oil and 0.1% to 1.3% protein content. Fludioxonil, boscalid/pyraclostrobin and fluopyram/prothioconazole achieved strongest fungicidal activity against SSR. The biopesticide provided 36% of disease control. Under in vitro conditions, B. amyloliquefaciens not only strongly inhibited mycelial growth but also the formation of sclerotia in all concentrations. Boscalid and fludioxonil exhibited the highest level of fungicidal activity against S. sclerotiorum, with mean EC50 values of 1.23 and 1.60 μg a.s. mL⁻¹. The highest variability of EC50 values between isolates was observed towards prothioconazole and azoxystrobin. Full article