1,721,013 research outputs found
Occurrence and infection of Cladosporium, Fusarium, Epicoccum and Aureobasidium in withered rotten grapes during post-harvest dehydration
No full textFungi like Cladosporium, Fusarium, Epicoccum and Aureobasidium can occur on withered grapes causing spoilage of passito wine. There is little or no information on the pathogenic role of these fungi. This study describes the isolation, incidence and identification of several isolates from different withered rotten grapes. Representative isolates grouped in several phenotypes were identified by phylogenetic analysis of internal transcribed spacer, actin or elongation factor gene sequences. Isolates of Cladosporium and Fusarium were ascribed to different species, of these C. ramotenellum, C. halotolerans and F. graminearum were isolated from Vitis vinifera for the first time. All Epicoccum and Aureobasidium isolates belonged to E. nigrum and A. pullulans, respectively. Random amplified DNA polymorphism analysis showed high level of heterogenicity among Epicoccum and Fusarium isolates. Infection assays were carried out to evaluate infectivity in some strains under different withering conditions. Fusarium spp. strains had similar infectivity, while significant variability was observed among Cladosporium spp. and E. nigrum strains. A. pullulans resulted particularly infective. This study provided insights into the occurrence and infection of these fungi in fruit-drying rooms with important implications towards control management during the witherin
Diaporthe rudis Associated with Berry Rot of Postharvest Grapes in Italy.
No full textGrapes for Italian passito wine production are subject to fungal decay during postharvest processing (withering). In January 2018, decayed berries of Vitis vinifera ‘Nosiola’ were observed in bunches stored in a fruit-drying room in Valle dei Laghi, Provincia Autonoma di Trento (Italy). The bunches displayed single or few berries with brown to dark brown discolorations and solitary or rarely aggregated, erumpent, black ascomata in the skin. The incidence of bunches with symptomatic berries was approximately 5%. Twelve small pieces (about 10 mm2) of epidermal and mesocarp berry tissues were sterilized in 0.5% NaOCl for 2 min, rinsed once in sterile distilled water, and then placed on potato dextrose agar (PDA). After 4 days at 25°C in the dark, fungal colonies showed similar morphology resembling cultures of Diaporthe spp. (Udayanga et al. 2014). Single-spore isolation was carried out to obtain pure cultures. Two representatives of these cultures (P19 [= CBS 145104] and P10) were identified by morphological and molecular analysis. On PDA, after 7 days at 25°C, colonies showed flat, entire edges, whitish to grayish, fluffy aerial mycelium. The reverse colony was light brown to gray, with dark brown pigmentation in the center. Mycelial PDA plugs (2.5 mm2) were transferred to alfalfa stems on water agar (15 g of agar/liter) as described by Udayanga et al. (2014). Pycnidia on alfalfa stems were black, globose, and erumpent at maturity. Conidiophores were hyaline, cylindrical, smooth, branched, ampulliform, straight to sinuous, 18 to 40 × 2 to 2.5 μm. Conidiogenous cells were cylindrical, terminal, with slight tapering toward apex (0.5 to 1 μm diameter). α-Conidia were hyaline, smooth, ellipsoidal, biguttulate, 5.7 ± 0.7 μm long, and 2.3 ± 0.4 μm wide (n = 40). β-Conidia were not observed. Species identification was performed by amplification of internal transcribed spacers, translation elongation factor 1-α, histone H3, and β-tubulin gene sequences using ITS1/ITS4, EF728/EF986, CYLH3F/H3-1b, and Bt2a/Bt2b primers, respectively (Guarnaccia et al. 2018). BLAST analysis and phylogenetic analysis, constructed with MEGA 7.0 software using the neighbor-joining method (evolutionary distances using the Tajima–Nei method) from combined multilocus databases, identified the isolates as Diaporthe rudis. The gene sequences were deposited in GenBank (accession nos. MH447355, MH447356, MH457708, MH457709, and MK205427 to MK205430). Pathogenicity testing was performed on 120 healthy partially dehydrated grape berries (cultivar Nosiola) with intact pedicel, surface sterilized by immersion in 0.5% NaOCl and rinsed three times in sterile distilled water. Each berry was inoculated with a 106 conidia/ml suspension of both isolates by piercing using a sterile tip (wounded berry, n = 50) or pipetting onto the berry surface (unwounded berry, n = 50). The control (20 berries) was inoculated with sterile water by piercing and pipetting. All inoculated withered berries were incubated at 25°C for 7 days at 95% relative humidity (RH). High RH values (>90%) are reached during the natural withering process depending on seasonal weather conditions. Disease index (DI), calculated for four disease severity classes in percentage, where DI = [sum (class frequency × score of rating class)]/[(total number of berries) × 4] × 100, of wounded and unwounded berries was approximately 26 and 18%, respectively. The frequent presence of microcracks and wounds on berry skin, owing to dehydration, handling, and insects that favor the fungal colonization, could explain the high DI values observed in unwounded berries. Symptoms on the infected berries were similar to those observed in the fruit-drying room. There were no symptoms on the control berries. The fungus was reisolated from the infected berries, thus completing Koch’s postulates. Although D. rudis has been recovered from asymptomatic and symptomatic grapevine (cane and leaf spots) (Guarnaccia et al. 2018), this is the first report of the fungus causing rot on grape fruit. Recently, D. eres, together with Pestalotiopsis biciliata and Diplodia seriata, has been associated with fruit rot in withered grapes (Lorenzini and Zapparoli 2018). This finding indicates that D. rudis may contribute, together with other pathogenic fungi, to the decay of grapes during the withering. Such decay is a major concern for producers because it could have a negative impact on wine quality
Corretta acidificazione nel formaggio grana attraverso la valutazione degli zuccheri residui nella cagliata
No full textBio-molecular characterisation of indigenous Oenococcus oeni strains from Negroamaro wine
No full textThe variation in the coding capacity within Oenococcus oeni can have a significant impact on wine quality. The detection of several genes involved in important metabolic pathways (i.e. citrate, sulphur and arginine metabolisms) was performed on 10 indigenous O.oeni strains from Negroamaro wine, a red table wine (Apulia, Italy). These strains were selected from 95 isolates, collected during spontaneous malolactic fermentation, according to the results of an Amplified Fragment Length Polymorphism (AFLP) analysis. A total of 16 genes were screened, most (11) of which had never previously been assayed on O.oeni. All strains possessed 10 genes encoding enzymes such as malolactic enzyme (mleA), esterase (estA), citrate lyase (citD, citE and citF), citrate transporter (maeP), α-acetolactate decarboxylase (alsD), α- acetolactate synthase (alsS), S-adenosylmethionine synthase (metK) and cystathionine β-lyase (metC) and resulted negative in the detection of genes encoding cystathionine γ-lyase (metB), ornithine transcarbamylase (arcB) and carbamate kinase (arcC). The sequence of PCR fragments of 11 genes of a representative strain (ITEM 15929) was compared to those of three reference O.oeni strains. The indigenous strain was phylogenetically more similar to PSU-1 and ATCC BAA1163 than AWRI B429. This study describes new genetic markers useful for detecting the genetic potential of O.oeni strains to contribute to aroma production and for investigating the population structure of the species. © 2014 Elsevier Ltd
A study on yeasts from valpolicella wines (Italy): identification and characterization of Saccharomyces sensu strictu strains by genetic and physiological methods
No full textLa fermentazione malolattica nei vini veronesi: l’esperienza dell’Università di Verona.
No full textAssessment of yeasts for apple juice fermentation and production of cider volatile compounds
No full textAt present, yeasts suitable for apple juice fermentation to produce cider have received scarce attention with respect to wine yeasts. In this study, Saccharomyces and non-Saccharomyces strains were investigated for their capacity to ferment apple juice and to influence the volatile compound production in cider. In a first fermentation trial, seven out of 18 yeasts, belonging to Saccharomyces cerevisiae, S. uvarum, Torulaspora delbrueckii, Hanseniaspora osmophila, H. uvarum, Starmerella bacillaris and Zygosaccharomyces bailii, were selected according to their fermentative performance. The effects of these strains on the volatile composition of cider, produced in a second apple fermentation trial, were then evaluated. Significant differences on the production of alcohols, esters and fatty acids were observed. Large amounts of 2-phenylethanol were found in S. uvarum cider. Hanseniaspora uvarum was the greatest producer of hexyl and isoamyl acetate among non-Saccharomyces yeasts. Ciders were well discriminated by principal component analysis. This study provides insights into the actual capacity to produce volatile compounds that the different yeast species that could be used in single or mixed apple juice fermentation for cider production
Saccharomyces bayanus var. uvarum and Saccharomyces cerevisiae succession during spontaneous fermentations of Amarone and Recioto wines
No full textThis study was undertaken to evaluate the biodiversity of the indigenous Saccharomyces
sensu stricto population during traditional vinification processes of Recioto and
Amarone wines using molecular typing techniques. In total 109 isolates, collected from eight
wineries during spontaneous fermentations, were identified and characterised by conventional
tests and by molecular methods, i.e. PCR fingerprinting using the primer (GTG)5,
mtDNA restriction and karyotype analyses. Sixty per cent of the isolates were assigned to
Saccharomyces bayanus var. uvarum and 40% to Saccharomyces cerevisiae. A succession
between S. bayanus var. uvarum, which dominated the first fermentation, and S. cerevisiae,
which appeared after the wine drawing-off operation, was observed during a traditional
Amarone winemaking. An extensive polymorphism was found between the isolates, however
a few specific genetic biotypes prevailed in the different wineries. This ecotaxonomic survey
constitutes a basic step to safeguard and exploit the oenological potential of the yeast
biodiversity in the Recioto and Amarone wine ecosystems. Such biodiversity could be further
explored to correlate the genetic patterns of the isolates with oenologically useful characteristics,
with the ultimate goal to carry out selection programmes of typical strains of the
Valpolicella area
- …
