An implementation framework for evaluating the biocidal potential of essential oils in controlling Fusarium wilt in spinach: from in vitro to in planta.

Fusarium wilt, caused by Fusarium oxysporum f. sp. spinaciae, causes a significant challenge on vegetative spinach and seed production. Addressing this issue necessitates continuous research focused on innovative treatments and protocols through comprehensive bioassays. Recent studies have highlighted the potential of plant-based compounds in controlling fungal diseases. The present work aims to conduct a series of experiments, encompassing both in vitro and in planta assessments, to investigate the biocontrol capabilities of different essential oils (EOs) at various application rates, with the ultimate goal of reducing the incidence of Fusarium wilt in spinach. The inhibitory effect of four plant EOs (marjoram, thyme, oregano, and tea tree) was initially assessed on the spore germination of five unknown Fusarium strains. The outcomes revealed diverse sensitivities of Fusarium strains to EOs, with thyme exhibiting the broadest inhibition, followed by oregano at the highest concentration (6.66 µL/mL) in most strains. The tested compounds displayed a diverse range of median effective dose (ED50) values (0.69 to 7.53 µL/mL), with thyme and oregano consistently showing lower ED50 values. The direct and indirect inhibitory impact of these compounds on Fusarium mycelial growth ranged from ~14% to ~100%, wherein thyme and oregano consistently exhibiting the highest effectiveness. Following the results of five distinct inoculation approaches and molecular identification, the highly pathogenic strain F-17536 (F. oxysporum f.sp. spinaciae) was chosen for Fusarium wilt assessment in spinach seedlings, employing two promising EO candidates through seed and soil treatments. Our findings indicate that colonized grain (CG) proved to be a convenient and optimal inoculation method for consistent Fusarium wilt assessment under greenhouse conditions. Seed treatments with thyme and oregano EOs consistently resulted in significantly better disease reduction rates, approximately 54% and 36% respectively, compared to soil treatments (P > 0.05). Notably, thyme, applied at 6.66 µL/mL, exhibited a favorable emergence rate (ERI), exceeding seven, in both treatments, emphasizing its potential for effective disease control in spinach seedlings without inducing phytotoxic effects. This study successfully transitions from in vitro to in planta experiments, highlighting the potential incorporation of EOs into integrated disease management for Fusarium wilt in spinach production.

Leguminous Seedborne Pathogens: Seed Health and Sustainable Crop Management.

Pulses have gained popularity over the past few decades due to their use as a source of protein in food and their favorable impact on soil fertility. Despite being essential to modern agriculture, these species face a number of challenges, such as agronomic crop management and threats from plant seed pathogens. This review's goal is to gather information on the distribution, symptomatology, biology, and host range of seedborne pathogens. Important diagnostic techniques are also discussed as a part of a successful process of seed health certification. Additionally, strategies for sustainable control are provided. Altogether, the data collected are suggested as basic criteria to set up a conscious laboratory approach.

Surveillance of Landraces' Seed Health in South Italy and New Evidence on Crop Diseases.

During the last three years, more than 300 landraces belonging to different plant species have been the main focus of an Italian valorization research project (AgroBiodiversità Campana, ABC) aiming at analyzing, recovering, preserving, and collecting local biodiversity. In this context, phytosanitary investigation plays a key role in identifying potential threats to the preservation of healthy seeds in gene banks and the successful cultivation of landraces. The surveillance carried out in this study, in addition to highlighting the expected presence of common species-specific pathogens such as Ascochyta pisi in peas, Ascochyta fabae in broad beans, and Macrophomina phaseolina, Xanthomonas axonopodis pv. phaseoli, and Xanthomonas fuscans subsp. fuscans in beans, pointed to the presence of novel microorganisms never detected before in the seeds of some hosts (Apiospora arundinis in common beans or Sclerotinia sclerotiorum and Stemphylium vesicarium in broad beans). These novel seedborne pathogens were fully characterized by (i) studying their morphology, (ii) identifying them by molecular methods, and (iii) studying their impact on adult crop plants. For the first time, this study provides key information about three novel seedborne pathogens that can be used to correctly diagnose their presence in seed lots, helping prevent the outbreaks of new diseases in the field.

Identification and Characterization of New Seedborne Pathogens in Phaseolus vulgaris Landraces of Southern Italy.

The diagnostic survey of seedborne fungal pathogens is fundamental for symptomless material stored in gene banks to avoid the diffusion of pathogens by germplasm distribution and propagation. In this work, seeds of Southern Italian landraces of the common bean (Phaseolus vulgaris L.) belonging to the gene bank at CREA (Italy) were inspected to assess their phytosanitary status. The phytopathological analysis revealed the presence of the most common pathogens associated with common bean seeds such as Fusarium spp., Macrophomina phaseolina, Rhizoctonia solani, Colletotrichum lindemuthianum and Diaporthe/Phomopsis complex. However, new fungi able to completely inhibit seed germination were also observed. The most aggressive were isolated, and the morpho-pathological characterization, DNA sequencing and phylogenetic analysis allowed us to define the strains as Botryosphaeria dothidea CREA OF 360.4 and Diplodia mutila CREA OF 420.36. These two plant pathogens are generally associated with grapevines and other fruit trees. Pathogenicity tests were carried out along with a transmissibility test in which the transmission of the pathogens to the seedlings was proven. Host range experiments revealed the ability of these pathogens to infect crops such as pepper and melon. To our knowledge, this is the first time that B. dothidea and D. mutila were detected on the common bean.

Occurrence of Macrophomina phaseolina on Chickpea in Italy: Pathogen Identification and Characterization.

Climate change has led to the spread of plant pathogens in novel environments, causing dramatic crop losses and economic damage. Botryosphaeriaceae represents a massive fungal family, containing a huge number of plant pathogens, which are able to infect several hosts. Among them, Macrophomina phaseolina is a necrotrophic fungus, responsible for several plant diseases, including the soft stem rot of common bean, crown rot on strawberry and charcoal rot of several legumes. Here, Macrophomina, causing crown charcoal rot in chickpeas, was isolated from symptomatic plants in Cicerale (SA), Campania, South Italy. Morphological and molecular characterization was carried out and pathogenicity tests were performed. Phylogenetic analyses were performed comparing Macrophomina strains coming from different geographic areas and hosts. The experiments confirmed the pathogenicity of the isolate CREA OF 189.2 on chickpea, while host range highlighted the polyphagous nature of this strain; thus, symptoms were reported on lentils, common bean and cantaloupe. The multidisciplinary approach allows us to increase the knowledge about this emerging pathogen. To the best of our knowledge, this is the first report on Macrophomina phaseolina from chickpeas in Italy.

Tomato genome-wide transcriptional responses to Fusarium wilt and Tomato Mosaic Virus.

Since gene expression approaches constitute a starting point for investigating plant-pathogen systems, we performed a transcriptional analysis to identify a set of genes of interest in tomato plants infected with F. oxysporum f. sp. lycopersici (Fol) and Tomato Mosaic Virus (ToMV). Differentially expressed tomato genes upon inoculation with Fol and ToMV were identified at two days post-inoculation. A large overlap was found in differentially expressed genes throughout the two incompatible interactions. However, Gene Ontology enrichment analysis evidenced specific categories in both interactions. Response to ToMV seems more multifaceted, since more than 70 specific categories were enriched versus the 30 detected in Fol interaction. In particular, the virus stimulated the production of an invertase enzyme that is able to redirect the flux of carbohydrates, whereas Fol induced a homeostatic response to prevent the fungus from killing cells. Genomic mapping of transcripts suggested that specific genomic regions are involved in resistance response to pathogen. Coordinated machinery could play an important role in prompting the response, since 60% of pathogen receptor genes (NB-ARC-LRR, RLP, RLK) were differentially regulated during both interactions. Assessment of genomic gene expression patterns could help in building up models of mediated resistance responses.