Loredana Sigillo

Rosmarinus officinalis (rosemary) is one of the most cultivated Lamiaceae species because of its medicinal, aromatic and ornamental properties. In the late summer of 2023, symptoms of desiccation were observed in a rosemary field located in southern Italy and the isolation from necrotic roots revealed three different fungal species: Ceratobasidium sp., Fusarium falciforme and Macrophomina phaseolina. All the isolates were morphologically and molecularly identified and Koch’s postulates assays were performed to establish the pathogenicity and the effect of each fungus on the disease incidence and severity. A dual plate method was used to investigate the interaction between Ceratobasidium sp., F. falciforme and M. phaseolina, mixing them in pairs and all together. Similarly, in vivo inoculations with the pathogens in combination were used to verify the role of each isolate in the interaction with the others and the contribution in plant disease expression. The results allowed to identify M. phaseolina and F. falciforme as causal agents of desiccation and root rot of rosemary, with M. phaseolina being the most aggressive between the two. Conversely, Ceratobasidium sp. behavior was influenced by the interaction with the other pathogens and the plant. Notably, this is the first report of M. phaseolina and F. falciforme on rosemary plants worldwide. This disease, caused by multiple pathogens, highlighted the crucial role of the combination of traditional in vivo assays and the use of molecular methods to achieve an accurate diagnosis.

Compost teas (CTs) can be considered natural microbial consortia, able to enhance biostimulation and defense in crops. This study focuses on two plant-derived CTs and their potential use as eco-friendly biofertilizers for chickpeas and peas, with the broader aim to protect soil fertility. Our experiments demonstrated that the two CTs have biostimulatory or inhibitory effects depending on dilution, target plant species, CT microbial load and metabolism, and age of CT preparation. Peas exhibited positive responses to treatments, while chickpeas could be negatively affected depending on CT concentration. The CT microbial load positively affected biostimulation for both plant species. The metabolic profiles of the CT-associated microbial communities were evaluated using the Biolog EcoPlate™ system. Spearman’s correlation analysis allowed us to ascertain a positive interaction between root elongation and the microbial consumption of specific substrates, namely polymers, erythritol, and L-serine. On the contrary, phenolic compound consumption showed a negative correlation. In chickpeas, root and collar necrosis, estimated with the McKinney index, increased after treatment with CTs at the highest concentration, confirming a phytotoxic effect; but diagnostic analyses demonstrated that the necrosis was also partially attributed to pathogenic Fusarium spp. On the other hand, proper dilutions of treatments determined a decrease in necrosis severity, indicating putative CT biocontrol properties.

Verticillium dahliae, the causal agent of vascular wilt, is a cosmopolitan pathogen of olive (Olea europaea L.). Italy is a traditional oil-producing country and its olive growing system is characterized by hundreds of regional varieties. They are widely employed for yielding oils protected by geographical indication systems of the European Union. The aim of this study was to evaluate the influence of V. dahliae on the vegetative growth of young, own-rooted olive plants under natural environmental conditions. Specifically, we analyzed differences in stem elongation, number of leaves and stem diameters in eight local varieties of the Campania region of Italy, plus a reference national cultivar, following artificially infection with a non-defoliating pathotype. Multivariate analysis indicated that a distinction in vulnerability among cultivar can be made considering the inhibitory effect of the fungus on stem extension growth, while the other parameters are less influential. Our work also illustrated the variability in some vegetative parameters among the Campanian germplasm and its influence on the inhibitory effect of the pathogen. Further studies will have to analyze the mechanisms connecting the morpho-physiological alterations with the pathogen invasion of the host tissue.

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.

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.

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.