Browsing by Author "Giorni, Paola"
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Item Open Access Comparison of different physical methods and preservatives for control of Fusarium proliferatum rot in garlic(MDPI, 2022-12-15) La Placa, Laura; Giorni, Paola; Mondani, Letizia; Magan, Naresh; Battilani, PaolaDry rot is an emerging issue for garlic production worldwide and Fusarium proliferatum is its major causal agent. Since the disease is seed-transmitted, sowing healthy cloves is crucial. In this study, some disinfection strategies were tested on garlic seeds, including steam, dry heat, chemical disinfectants and gaseous ozone (O3). Steam reduced the Colony Forming Units·g−1 (CFUs·g−1) by up to 92% in garlic seeds, but, at the same time, it affected their germination (−36%). Similarly, hydrogen peroxide (H2O2) and peracetic acid (C2H4O3) reduced the CFUs·g−1 by up to 83%; however, these methods also severely impaired germination (−40%). Dry heat did not negatively impact germination, but fungal contamination was not significantly reduced. The most promising strategy was gaseous O3 treatment; it decreased CFUs·g−1 by up to 96%, without causing any reduction of germination. The treatments applied were partially effective because the fungus is predominantly located in the outer layer of the seed, although it is also found in the inner portions. Some of these treatments can contribute to garlic protection from seed-borne pathogens and possibly reduce the occurrence of garlic dry rot.Item Open Access Effect of solute and matric potential on in vitro growth and sporulation of strains from a new population of Aspergillus flavus isolated in Italy.(Elsevier, 2008-05) Giorni, Paola; Battilani, Paola; Magan, NareshThe effect of temperature and different solute (Ψs) and matric potentials (Ψm) on growth and sporulation of three aflatoxigenic strains of Aspergillus flavus isolated from contaminated maize in northern Italy was determined. The Ψs of maize-based media were modified ionically (NaCl) and non-ionically (glycerol) and the Ψm with PEG 8000 in the range −1.4 to −21.0 MPa at 25 and 30 °C. Both temperature and Ψs/Ψm stress had statistically significant effects on growth rates of the three strains. Faster growth occurred at 30 °C and −1.4 and −2.8 MPa. A. flavus strains were more sensitive to Ψm than Ψs stress with limits of −9.8 MPa and −14 to−18 MPa, respectively. Sporulation was significantly influenced by Ψs potential, solute type and temperature. This suggests that these aflatoxigenic strains of A. flavus isolated from aflatoxin-contaminated maize are probably able to colonise crop debris rapidly at prevailing temperatures and water stress conditions. This type of information on the ecology of aflatoxin producing A. flavus strains isolated in Italy will contribute to the development of a systems model to predict their activity in crop residue and colonisation of maize grain.Item Open Access Environmental factors modify carbon nutritional patterns and niche overlap between Aspergillus flavus and Fusarium verticillioides strains from maize.(Elsevier, 2009-04-15) Giorni, Paola; Magan, Naresh; Battilani, PaolaThis study examined the utilization patterns of key carbon sources (CS, 24: including key sugars, amino acids and fatty acids) in maize by strains of Aspergillus flavus and Fusarium verticillioides under different water activity (aw, 0.87–0.98 aw) and temperature (20–35 °C) values and compared the niche overlap indices (NOI) that estimate the in vitro CS utilization profiles [Wilson, M., Lindow, S.E., 1994. Coexistence among epiphytic bacterial populations mediated through nutritional resource partitioning. Applied and Environmental Microbiology 60, 4468–4477.]. The ability to grow in these key CS in minimal media was studied for 120 h in 12 h steps. The NOI was calculated for inter-species (F. verticillioides–A. flavus) and for intra-species (A. flavus–A. flavus) using CS utilization patterns over the range of interacting environmental conditions. 30 °C, over the whole aw range examined, was found to be optimal for utilization of the maximum number of CS by A. flavus. In contrast, for F. verticillioides this was more so at 20 °C; 25 °C allowed a suboptimal usage of CS for both species. NOIs confirmed the nutritional dominance of A. flavus at 30 °C, especially at lower aw levels and that of F. verticillioides at 20 °C, mainly at 0.95 aw. In other conditions of aw, based on CS utilization patterns, the data indicated that A. flavus and F. verticillioides occupied different ecological niches. The variability in nutritional sources utilization between A. flavus strains was not related to their ability to produce aflatoxins (AFs). This type of data helps to explain the nutritional dominance of fungal species and strains under different environmental conditions. This could be useful in trying to find appropriate natural biocontrol microorganisms to compete with these mycotoxigenic species.Item Open Access Impact of environmental and plant factors on Aspergillus section Flavi isolated from maize in Italy(Cranfield University, 2007-12) Giorni, Paola; Magan, Naresh; Battilani, PaolaThe exceptional hot weather conditions in Italy during the summer of 2003 resulted in an optimal environment for the development of Aspergillus section Flavi in maize and, consequently, for aflatoxin production. This caused significant contamination, above the EU legal limits, for maize destined to feed and food. This study was focused to define the distribution of these fungi in Italy for the first time. In all the sampled regions of Northern Italy, A. flavus was present. Ecological studies were conducted and this defined the cardinal conditions of water availability (0.83-0.99 aw), temperature (15-45°C) and gas composition (CO2<50%) for sporulation, growth and aflatoxin B1 production. Since in the field A. flavus does not occur alone, possible interactions with the fumonisin producing species Fusarium verticillioides was examined by using carbon source utilisation patterns and niche overlap indices. F. verticillioides was a better competitor over the range 0.93-0.98 aw and temperature of 20°C while A. flavus dominated at 0.98 aw and 30°C. Inoculum concentration (10 1 -10 7 CFUs ml) affected infection efficiency, with a low percentage of kernels becoming infected with up to 10 5 conidia mL -1 , and early maize growth stages were more susceptible. A total of 34 maize hybrids were screened for resistance to A. flavus and aflatoxin production and this showed that about 40% of these showed promise. The data sets obtained in this study wil provide a powerful basis for the development of a Decision Support System to minimize aflatoxins in maize.