title: Hydro- and thermotimes for conidial germination kinetics of the ochratoxigenic species Aspergillus carbonarius in vitro, on grape skin and grape flesh.
abstract: The objective was to compare the ability of spores of Aspergillus carbonarius to germinate in vitro, in situ on grape skin and grape flesh in relation to temperature (15-40 °C) and different relative humidities (100-85% RH). Spores were inoculated as a spore suspension (10(6) spores ml(-1)) onto the surface of white organic grapes and directly onto cut grape flesh. For comparison, spores were spread plate onto a synthetic grape juice medium (SGM) modified to the equivalent water activity (a(w)) range of 0.995-0.85. This showed that conidia germinated more rapidly on grape flesh (6 h) followed by that on the SGM medium (9 h) and then grape skin (24 h) under optimal condition of 30-35 °C and 100 % RH. At marginal conditions, such as 15 °C and 85-90% RH, germination was very slow. The time to 5% germination was significantly shorter on grape flesh than in vitro on grape medium and slowest on grape skin. This suggests that damaged grapes provide the main method of infection and contamination of grapes and grape products with ochratoxin A (OTA). The combined effect of temperature and RH on conidial germination of A. carbonarius on SGM and grape skin was described by combining Beta and polynomial equations. The equations developed in this work provided a good fit of the biological processes; they could be integrated in a predictive model for infection and OTA prediction in ripening grapes.
authors.affiliation: Institute of Entomology and Plant Pathology, Università Cattolica del Sacro Cuore, via Emilia Parmense 84, 29100 Piacenza, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Camardo Leggieri
authors.affiliation: Applied Mycology Group, Cranfield Soil and AgriFood Institute, Cranfield University, Bedford MK43 0AL, UK.
authors.forename: David
authors.initials: D
authors.lastname: Mitchell
authors.affiliation: Applied Mycology Group, Cranfield Soil and AgriFood Institute, Cranfield University, Bedford MK43 0AL, UK.
authors.forename: David
authors.initials: D
authors.lastname: Aldred
authors.affiliation: Institute of Entomology and Plant Pathology, Università Cattolica del Sacro Cuore, via Emilia Parmense 84, 29100 Piacenza, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Battilani
authors.affiliation: Applied Mycology Group, Cranfield Soil and AgriFood Institute, Cranfield University, Bedford MK43 0AL, UK. Electronic address: n.magan@cranfield.ac.uk.
authors.forename: Naresh
authors.initials: N
authors.lastname: Magan
mesh_terms: D001230:Aspergillus / Q000254:growth & development*; D003470:Culture Media / Q000737:chemistry; D005506:Food Contamination / Q000032:analysis; D005516:Food Microbiology; D005638:Fruit / Q000382:microbiology; D009793:Ochratoxins / Q000032:analysis; D013172:Spores, Fungal / Q000254:growth & development*; D027843:Vitis / Q000382:microbiology*; D014867:Water / Q000737:chemistry
chemical_list: D003470:Culture Media; D009793:Ochratoxins; D014867:Water; C025589:ochratoxin A
keywords: Conidial germination; Ochratoxigenic fungi; Pathogen infection; Prediction; Relative humidity; Temperature