Domenica Villecco

Novel strains of Bacillus, isolated from compost and compost-amended soils, as biological control agents against soil-borne phytopathogenic fungi

Abstract A stepwise screening strategy made it possible to identify five new Bacillus spp. strains for biocontrol of Rhizoctonia solani, Sclerotinia minor and Fusarium solani. In vitro and in vivo biocontrol 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 to Bacillus subtilis group as Bacillus amyloliquefaciens- and Bacillus 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 on Brassica oleracea/R. solani pathosystem, 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. Bacillus strains isolated from compost and compost-amended soils are promising BCAs that have potential for practical application as biofungicides.

Effects of on-farm composted tomato residues on soil biological activity and yields in a tomato cropping system

BackgroundThe use of compost may relieve the factors that limit productivity in intensive agricultural systems, such as soil organic matter depletion and soil sickness. Concomitantly, the practice of on-farm composting allows the recycle of cropping green residues into new productive processes.ResultsWe produced four vegetable composts by using tomato biomass residues in an on-farm composting plant. The tomato-based composts were assessed for their chemical, microbiological properties, and their effects on soils and plants were evaluated after their application within a tomato cropping system. Compost characteristics affected plant development and productivity through increased nutrient uptake and biostimulation functions. Soil biological activities, including basal respiration, fluorescein diacetate hydrolysis, β-glucosidase, dehydrogenase, alkaline phosphatase, arylsulphatase, and Biolog community levels of physiological profiles, were differently affected by the on-farm tomato-based composts.ConclusionsChanges in soil activity and community structure due to compost amendments were related to classes of biomolecules such as polysaccharides and lignin-derived compounds, as revealed by nuclear magnetic resonance (NMR) spectra of compost materials. The nutrient content and fertility potential of composts were positively related to the amount of tomato residues present in the feedstock.

Integration of soil solarization with Brassica carinata seed meals amendment in a greenhouse lettuce production system.

Abstract The use of integrated pest management is a valid alternative to conventional chemical treatments. This study was carried out to evaluate the effects of Brassica carinata seed meals amendment, combined with solarization, on soil activity and lettuce cultivation. B. carinata seed meals pellets are biofumigant plant tissues originated as byproducts of the biodiesel industry. Microbiological data combined with lettuce production results suggest that, after biofumigation, soil microbial communities change toward a new equilibrium that creates better root plant conditions to improve high lettuce yields. Moreover, Brassica seed meals, combined with solarization, preserved soil microflora against detrimental effects of heating, as revealed by enzymatic and functional analysis.

Screening of plant-derived antifungal substances useful for the control of seedborne pathogens

The effect of plant essential oils, Solanum chilense and Aster sedifolius raw saponins, plant-derived colourants and Brassica carinata glucosinolate-containing tissues, for the control of seedborne fungi Alternaria dauci, Alternaria radicina, Colletotrichum lindemuthianum and Ascochyta rabiei, was evaluated. In vitro assays indicated that oregano essential oil, bark chestnut-derived colourant and B. carinata meals, showed a large spectrum of activity against all pathogens. S. chilense raw saponins were effective against A. dauci and A. radicina, while those from A. sedifolius also inhibited significantly C. lindemuthianum. Screening showed the antifungal potential of natural compounds.

Short-Time Response of Microbial Communities to Waste Compost Amendment of an Intensive Cultivated Soil in Southern Italy

In an intensely cultivated soil in southern Italy, the effects of municipal waste compost on soil activities (basal respiration, β-glucosidase, and fluorescein diacetate (FDA) hydrolysis), Biolog functional diversity, pH, and electrical conductivity (EC) were estimated in a short period following amendment. Treatment with compost at 30 t ha−1 (dry matter) was compared to mineral fertilization and untreated soil. In these poor soils, organic amendment allowed the rapid recovery of an active and biodiverse soil community. While the addition of compost increased all microbial activities and EC, the pH did not change. Conversely, metabolic activity that was positively correlated to FDA hydrolysis rate initially was enhanced by compost but decreased with time and disappeared at the end of the incubation. Results indicated that waste compost amendments affected microbial activities, both at global and functional levels, favoring a rapid return of biological factors of fertility.

Comparison among recognized and non-recognized Phaseolus vulgaris L. landraces as traditional agro-food products of the Campania region (Italy)

Efforts to safeguard and promote the on-farm maintenance of common bean (Phaseolus vulgaris L.) landraces should take seed quality into high consideration. Seed quality, in addition to suitable agronomic performances, is a good criterion to identify the most interesting materials among those traditionally cultivated. Ten landraces, still cultivated in the Campania region (southern Italy), were investigated. Five of these landraces, recognized as regional traditional agro-food products, are included in the list of the Italian typical products. Landraces belonging to both Mesoamerican and Andean common bean gene pools were present in the ten studied materials. The harvests of two subsequent growing seasons were analysed in order to compare the physico-chemical, culinary and nutritional seed quality of, recognised or not, landraces. Eighteen agronomic and nutritional traits were scored. When individually considered, none of the scored traits was able to discriminate the two groups of landraces. Conversely, submitting all traits to cluster analysis, two sub-clusters corresponding to recognised or not traditional products were obtained. Two landraces, one for each group, remained isolated. On the bases of these results, it can be inferred that the landraces recognized as traditional agro-food products have different culinary and nutritional characteristics in respect to the non-recognized ones.