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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. [ABSTRACT FROM AUTHOR]

Garden cress is a vegetable crop in the Brassicaceae family that is appreciated for its nutraceutical and taste-giving components in minimally processed food chains. Due to its very short cycle, which depends on the range of production from microgreens to baby-leaf vegetables, this crop is threatened by soil-borne pathologies developing within the initial stages of germination and emergence. This study aims to evaluate the suppressive bio-compost as an innovative means to counteract the main telluric diseases of garden cress and reduce the risks of yield loss by adopting sustainable remedies and decreasing the dependence on synthetic fungicides. Therefore, eleven green composts obtained using both previously distilled and raw aromatic plant residues were analyzed for suppressive properties against Rhizoctonia solani and Sclerotinia sclerotiorum on sown garden cress. The biological active component of the composts, detected by CO2-release, FDA-hydrolysis and microbial counts, proved to be indispensable for pathogen control in vitro and in vivo, as demonstrated by the loss of suppressiveness after sterilization. Cross-polarization magic angle spinning 13C-nuclear magnetic resonance (CP-MAS-13C-NMR) was used to analyze the molecular distribution of organic C in composts. The results indicated the suitability of the feedstock used to make quality compost. The suppression levels shown by composts P1 (40% wood chips, 30% escarole and 30% a mixture of sage, basil, mint and parsley) and P2 (40% wood chips, 30% escarole and 30% a mixture of essential oil-free sage, basil and rosemary) are promising for the sustainable, non-chemical production of garden cress vegetables. [ABSTRACT FROM AUTHOR]

Research has been increasingly focusing on the selection of novel and effective biological control agents (BCAs) against soil-borne plant pathogens. The large-scale application of BCAs requires fast and robust screening methods for the evaluation of the efficacy of high numbers of candidates. In this context, the digital technologies can be applied not only for early disease detection but also for rapid performance analyses of BCAs. The present study investigates the ability of different Trichoderma spp. to contain the development of main baby-leaf vegetable pathogens and applies functional plant imaging to select the best performing antagonists against multiple pathosystems. Specifically, sixteen different Trichoderma spp. strains were characterized both in vivo and in vitro for their ability to contain R. solani, S. sclerotiorum and S. rolfsii development. All Trichoderma spp. showed, in vitro significant radial growth inhibition of the target phytopathogens. Furthermore, biocontrol trials were performed on wild rocket, green and red baby lettuces infected, respectively, with R. solani, S. sclerotiorum and S. rolfsii. The plant status was monitored by using hyperspectral imaging. Two strains, Tl35 and Ta56, belonging to T. longibrachiatum and T. atroviride species, significantly reduced disease incidence and severity (DI and DSI) in the three pathosystems. Vegetation indices, calculated on the hyperspectral data extracted from the images of plant- Trichoderma -pathogen interaction, proved to be suitable to refer about the plant health status. Four of them (OSAVI, SAVI, TSAVI and TVI) were found informative for all the pathosystems analyzed, resulting closely correlated to DSI according to significant changes in the spectral signatures among health, infected and bio-protected plants. Findings clearly indicate the possibility to promote sustainable disease management of crops by applying digital plant imaging as large-scale screening method of BCAs' effectiveness and precision biological control support. [ABSTRACT FROM AUTHOR]

In the present study, 26 accessions of rocket salad belonging to four species (Eruca sativaMill.,Diplotaxis tenuifolia(L.) DC.,Diplotaxis muralis(L.) DC. andErucastrum spp.) were tested for resistance to damping-off, wilting and leaf spot disease causal agents. High susceptibility toRhizoctonia solaniwas detected in all accessions while variability in rocket seedling susceptibility forSclerotiniaassays was observed. Susceptibility to wilting caused by the fungusFusarium oxysporumf. sp.raphaniwas tested.E. sativavarieties exhibited a lower severity degree associated to yellowing-related symptoms compared toD. tenuifolia. Resistance assay using the bacteriumXanthomonas campestrispv.campestriswas also performed. FiveE. sativavarieties showed a disease incidence lower than 60% while all theD. tenuifoliaaccessions, showed a susceptibility of 100%. The present study represents a step towards the identification of genetic resources useful in breeding for the selections of novel resistant varieties. [ABSTRACT FROM PUBLISHER]

A stepwise screening strategy made it possible to identify five newBacillusspp. strains for biocontrol ofRhizoctonia solani,Sclerotinia minorandFusarium solani.In vitroandin vivobiocontrol activity and M13-PCR DNA-fingerprinting led to the selection of these valuable biological control agents (BCAs) from a wide collection of over 250 candidates. At the end of this selection, the highest potential antagonists were identified at species level by 16S-rRNA gene sequence analysis, and results assigned them toBacillus subtilisgroup asBacillus amyloliquefaciens-andBacillus methylotrophicus-related strains. In the current study, spore-forming bacteria provided substantial biocontrol of telluric diseases on cress and other different host plants. The strains named 15S and 09C were effective in disease control onBrassica oleracea/R. solanipathosystem, whereas Sclerotinia drop of lettuce was reduced by treatments with the strains 17S and 08C. Finally, the strains 17S and 12S were equally effective to control potato Fusarium rot. The evident zone of inhibition seen in dual culture plates suggested antibiosis-like antagonisms as the main mechanisms used by these bacterial isolates in interaction with the pathogens. Additionally, the API-ZYM method revealed constitutive activity of certain extracellular enzymes that could be involved in plant fortification.Bacillusstrains isolated from compost and compost-amended soils are promising BCAs that have potential for practical application as biofungicides. [ABSTRACT FROM AUTHOR]

Plants produce a huge array of secondary metabolites that play a key role in defense mechanisms against detrimental microorganisms and herbivores, and represent a suitable alternative to synthetic fungicides in sustainable agriculture. In this work, twelve crude hydroethanolic extracts derived from leaves of different potato cultivars were chemically characterized by LC/MS and their antioxidant properties were investigated in vitro. Furthermore, the biological activity against the fungal pathogen Rhizoctonia solani was evaluated both in vitro and in vivo. Extracts showed the ability to inhibit R. solani growth in vitro and significantly reduced damping-off incidence in in vivo experiments. Furthermore, R. solani mycelia exposed to the extracts showed an altered morphology (low translucency, irregular silhouette, and cytoplasmatic content coagulation) compared to the untreated control in light microscopy examination. Principal component analysis conducted on identified chemical compounds highlighted significant metabolic variations across the different extracts. In particular, those that inhibited most of the growth of the pathogen were found to be enriched in α-chaconine or α-solanine content, indicating that their biological activity is affected by the abundance of these metabolites. These results clearly indicated that plant-derived compounds represent a suitable alternative to chemicals and could lead to the development of new formulates for sustainable control of plant diseases. [ABSTRACT FROM AUTHOR]

In the present study, 133 bacterial isolates from 11 composted aromatic plant wastes were selected for their ability to inhibit the mycelial growth of the soil-borne phytopathogenic fungi Sclerotinia minor and Rhizoctonia solani. Successively, a subset of 35 from them were further characterized for their ability to control, in vivo, rocket damping-off caused by the two fungi. Moreover, the isolates were characterized for morphology of the colonies, Gram reaction, siderophore production, P-solubilization and for the presence of antimicrobial lipopeptide genes in the genome. The screening for the in vitro antagonisms showed a mycelial growth reduction ranging between 31.7% and 56.1% for R. solani and 34.4% and 59.4% for S. minor. All the isolates were not able to produce siderophores and some of them were able to solubilize P. The isolates contained two or more of the five lipoproteins coding genes investigated in this study. The most promising isolates were identified at species level by 16S-rRNA partial gene sequence analysis and were grouped in two main clusters related to Bacillus subtilis and Bacillus amyloliquefaciens reference strains. Results indicated that Bacillus isolates from compost are good candidates for application in the biocontrol of cultivated plants. [ABSTRACT FROM AUTHOR]

Abstract: On-farm composting is an efficient, environmentally safe and cost-effective process for recycle vegetable residues into productive cycles. Benefits of these composts could include their ability to mediate soil-borne plant pathogen suppression with a significant impact on eco-friendly crop management. In this work, on-farm composts were assayed for ability to control, both in vitro and in vivo, damping-off causing pathogens Rhizoctonia solani and Sclerotinia minor. Tomato and escarole-derived compost was the most suppressive and, furthermore, together with that derived from artichoke wastes, exhibited multi-suppressive activity. Compost communities, characterized at metabolic and global levels by Biolog system, microbial counting, CO2-release and FDA hydrolysis rate, play a major role in compost-based biological control. The complete biotic inactivation by autoclaving composts, has, in fact, reduced or eliminated their ability in pathogen suppression. Solid state 13C CPMAS-NMR spectroscopy revealed that spectral areas typical for phenolic C, as well as methoxyl C, may be associated to suppressivity mechanism(s). These evidences suggested that the ecological relationships between organic carbon molecular distribution and microbial structure may contribute to discriminate suppressive composts from null and conducive ones. Nutritional microniches in compost may then have profound effects on the community functions, including those linked to the suppressiveness. [Copyright &y& Elsevier]

• Leafy vegetable/cardoon residues were composted by three different on-farm methods. • Compost suppressiveness was assessed against two soil-borne pathogens. • Microbial activity and diversity into compost is crucial for suppressiveness. • Biodegradable C sustained microbial disease suppression in actively aerated compost. • Linear and microbial fatty acids supported antagonisms in passive aerated compost. On-farm composting is suitable to recycle agricultural biomasses in mature and stable organic matter that can be applied to improve the general soil conditions, such as physical, chemical, hydro-physical, texture, and refresh the provided ecosystem services for human well-being. Quality compost have a high potential in sustaining plant health through disease suppressiveness mechanisms against soil-borne pathologies; however, this property needs to be standardized. In this work, leafy vegetable/chipped energy cardoon residues have used as common starting feedstock in three comparative composting piles differentiated for the aeration method (passive, active and manual turning). Compost from both passively and actively aerated static piles showed higher suppressive properties against Lepidium sativum damping-off caused by Rhizoctonia solani and Sclerotinia minor. The enhanced suppressiveness was found associated to increased population levels of fungi and bacteria, combined with larger microbial activity and catabolic diversity. Compost community levels of physiological profiles were distributed within PCA biplots according to the gradient of suppressiveness and, putatively, their C-food bioavailability degree. The observed differences in stimulation and selection of microbiota may be related to specific molecular compost features. The two suppressive compost revealed either a distinct lipid composition, assessed by thermochemolysis and to the preservation of readily biodegradable molecules by lignocellulosic components, as detected in NMR analyses. Findings indicate the relevance of on-farm composting methods in shaping compost suppressive functions and give new information about the provisioning of bio-based products for sustainable plant disease management. [ABSTRACT FROM AUTHOR]