|De Aurreocoechea, I.|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2004
Publication Date: 3/24/2004
Citation: Vero, S., Garat, F., Silvera, E., De Aurreocoechea, I., Wisniewski, M.E. Biocontrol activity of two yeast strains from uruguay against blue mold of citrus. Meeting Abstract. Abstract 02-17 presented at the International Workshop, "Development of Biocontrol Agents of Fungal Disease for Commercial Applications in Food Production Systems", Seville, Spain, March 24-27, 2004. Interpretive Summary:
Technical Abstract: Citrus is the most important fruit produced in Uruguay. Citrus fruit, especially oranges, is destined for internal consumption and is also exported to Mercosur and European countries. Time to reach European markets is about one month. During this period, fruit is stored at low temperatures (5°C for oranges). However, rots due to pathogenic fungi appear causing great losses in many cases. Currently, synthetic fungicides are applied on harvested fruit as a primary means of controlling postharvest diseases in conventional production. The process includes a wash with sodium hypochlorite, a drench with sodium orthophenylphenate (SOPP), and then application of thiabendazole (TBZ) and or imazalil (IMZ) on packing line in aqueous or wax treatments. Public concern and regulatory restrictions on current pesticides have emphasized the need to find alternative methods for disease control. In recent years, biological control has been explored as an alternative to the use of synthetic fungicides for managing postharvest decay. This work describes the first trials to develop an integrated management for the control of blue mold of citrus in Uruguay. The first step of this study consisted of the isolation, identification and characterization of native strains causing blue mold of citrus in Uruguay. Strains belonging to Penicillium italicum and Penicillium ulaiense species were isolated and characterized by aggressiveness on fruit and fungicide resistance. The most aggressive pathogenic strain was chosen to be used as the pathogen in biocontrol assays. In order to find native antagonists to control pathogen development, superficial flora from healthy fruit that had been stored for more than one month at 5ºC was isolated. Those isolates that were able to grow at 5ºC on PDA were selected for further study. Biocontrol assays on fruit at 5ºC were performed using the selected isolates as antagonists. Two yeast antagonists, Leucosporidium scotti PL 9 and Cystofilobasidium infirmominiatum PL1, were chosen because they reduced blue mold incidence by more than 85%. Identification of the antagonists was confirmed by sequencing ITS1-5.8SrRNA-ITS2 regions and comparing the sequences with those deposited in NCBI data base. This is the first report of these species as biocontrol agents of blue mold of citrus. Optimal growth temperature and pH was determined for each isolate. Resistance of the two antagonists to imazalil and thiabendazole was assayed in vitro to determine the minimum concentration of fungicide that could be used in an integrated control strategy. Minimal inhibitory concentration of chitosan and glycolchitosan was also determined for native antagonists to know if those polymers could be applied together with antagonists in order to potentate biocontrol of blue mold.