Browsing by Author "Diaz, Gonzalo A."

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    Characterization of Botrytis cinerea and B. prunorum From Healthy Floral Structures and Decayed 'Hayward' Kiwifruit During Post-Harvest Storage
    (AMER PHYTOPATHOLOGICAL SOC, 2021) Riquelme, Danae; Aravena, Zdenka; Valdes Gomez, Hector; Latorre, Bernardo A.; Diaz, Gonzalo A.; Pablo Zoffoli, Juan
    Gray mold is the primary postharvest disease of 'Hayward' kiwifruit (Actinidia deliciosa) in Chile, with a prevalence of 33.1% in 2016 and 7.1% in 2017. Gray mold develops during postharvest storage, which is characterized by a soft, light to brown watery decay that is caused by Botrytis cinerea and B. prunorum. However, there is no information on the role of B. prunorum during the development and storage of kiwifruit in Chile. For this purpose, asymptomatic flowers and receptacles were collected throughout fruit development and harvest from five orchards over two seasons in the Central Valley of Chile. Additionally, diseased kiwifruits were selected after storage for 100 days at 0 degrees C and 2 days at 20 degrees C. Colonies of Botrytis sp. with high and low conidial production were consistently obtained from apparently healthy petals, sepals, receptacles, and styles and diseased kiwifruit. Morphological and phylogenetic analysis of three partial gene sequences encoding glyceraldehyde-3-phosphate dehydrogenase, heat shock protein 60, and DNA-dependent RNA polymerase subunit II were able to identify and separate B. cinerea and B. prunorum species. Consistently, B. cinerea was predominantly isolated from all floral parts and fruit in apparently healthy tissue and diseased kiwifruit. During full bloom, the highest colonization by B. cinerea and B. prunorum was obtained from petals, followed by sepals. In storage, both Botrytis species were isolated from the diseased fruit (n = 644), of which 6.8% (n = 44) were identified as B. prunorum. All Botrytis isolates grew from 0 degrees C to 30 degrees C in vitro and were pathogenic on kiwifruit leaves and fruit. Notably, B. cinerea isolates were always more virulent than B. prunorum isolates. This study confirms the presence of B. cinerea and B. prunorum colonizing apparently healthy flowers and floral parts in fruit and causing gray mold during kiwifruit storage in Chile. Therefore, B. prunorum plays a secondary role in the epidemiology of gray mold developing in kiwifruit during cold storage.
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    Germicidal effect of UV light on epiphytic fungi isolated from blueberry
    (PONTIFICIA UNIV CATOLICA CHILE, FAC AGRONOMIA INGENIERIA FORESTAL, 2012) Latorre, Bernardo A.; Rojas, Susana; Diaz, Gonzalo A.; Chuaqui, Hernan
    B.A. Latorre, S. Rojas, G.A. Diaz, and H. Chuaqui. 2012. Germicidal effect of UV light on epiphytic fungi isolated from blueberry. Cien. Inv. Agr. 39(3): 473-480. The present study examined the inactivation effect of ultraviolet (UV) light on the conidia of Botrytis cinerea Cladosporium cladosporioides, C. herbarum and Pestalotiopsis clavispora, common pathogens of blueberry (Vaccinium corymbosum), often found as epiphytes. The fungi were grown at 20 degrees C in acidified potato dextrose agar (APDA) in the dark; conidial suspensions (10(6) conidia mL(-1)) were placed the bottom of 5 cm glass Petri plates with a maximum height of 0.5 mm. Uncovered plates were immediately exposed to either UVA (lambda = 361 nm), UVB (lambda = 302 nm) or UVC (lambda = 254 nm) at doses between 40 and 110 mJ.cm(2). The results were expressed as survival ratios Nt/N0 (the number of colonies obtained after conidia were exposed to UV irradiance/the total number of fungal colonies in the non-irradiated controls). The fungal-dependent rate constants (k), a measure of the mortality rate, were estimated from an exponential model. The species in order of greatest to least resistance to UV light were Cladosporium cladosporioides, C. herbarum, R clavispora and B. cinerea. The type of fungal species and the dose of UV irradiance had a significant (P <= 0.001) influence on Nt/N0. The interaction between the fungal species and the UV irradiance dose was significant (P <= 0.004) only when the conidia were exposed to UVB or UVC. The resistance of Cladosporium spp. to UV radiation may explain the ubiquity of Cladosporium spp. in nature and could allow for the abundant populations of Cladosporium spp. often found on the foliage, flowers and fruits of blueberries.
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    Low Occurrence of Patulin-Producing Strains of Penicillium in Grapes and Patulin Degradation during Winemaking in Chile
    (AMER SOC ENOLOGY VITICULTURE, 2011) Diaz, Gonzalo A.; Yanez, Lina; Latorre, Bernardo A.
    Penicillium expansum has emerged as the cause of storage decay of table grapes (Vitis vinifera) and has been frequently isolated from apparently healthy clusters of grapes in Chile. The objectives of this study were to identify patulin-producing strains of Penicillium associated with winegrapes and wineries in Chile and to determine the potential presence of patulin in wines made with grapes infected with P. expansum. In this study, P. brevicompactum, P. expansum, and P. glabrum were identified on apparently healthy grape clusters and in the air of vineyards and wineries. Of 132 Penicillium isolates, 4 P. brevicompactum and 11 P. expansum strains were patulin-producing, determined by HPLC-UV/DAD. Patulin was also detected in Cabernet Sauvignon musts produced with grapes contaminated with a patulin-producing strain of P. expansum. However, patulin concentrations decreased during fermentation by 67.3 to 83.3%. Overall, the frequency of P. expansum isolation from grapes was relatively low; thus, considering the rapid degradation of patulin produced during fermentation, the risk of patulin contamination of bottled wine appears to be low.
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    Ochratoxigenic Aspergillus species on grapes from Chilean vineyards and Aspergillus threshold levels on grapes
    (ELSEVIER, 2009) Diaz, Gonzalo A.; Torres, Rene; Vega, Mario; Latorre, Bernardo A.
    This study reports the incidence of ochratoxigenic strains of Aspergillus on Chilean grapes (Vitis vinifera) and wineries, and production of OTA levels in wines with grapes having different levels of contamination with OTA-producing Aspergillus carbonarius was studied. A. carbonarius, A. niger, A. niveus, A. paradoxus, A. versicolor, A. wentii, and A. westerdijkiae were identified on apparently healthy clusters of red and white grape cultivars. However, A. carbonarius and A. niger were the most frequently identified species, mow abundant on red than white grape cultivars. Aspergillus spp. populations increased between veraison and harvest, but the isolation frequencies were relatively low over the entire growing season. At the winery, A. carbonarius, A. niger and A. westerdijkiae were occasionally found in the air, exclusively during winemaking. OTA-producing strains were only found among isolates of A. carbonarius, A. niger, A. wenti, and A. westerdijkiae. producing 2 to 17 mu g/L of OTA in liquid medium; however, A. westerdijkiae produced the highest OTA concentration in vitro. Red wines elaborated with 0.5% of grapes infected with an OTA-producing strain of A. carbonarius (Aspuc-SB36) exceeded the 2 mu g/L of OTA tolerance established for wines by the European Community. Therefore, a threshold below 0.5% infected berries is proposed for red wines. ELISA tests proved to be useful for detecting OTA in broth culture as in wine samples. (C) 2009 Elsevier B.V. All rights reserved.