Evaluación del potencial de dos cepas de Kluyveromyces thermotolerans como agentes de biocontrol de Aspergillus sección Nigri y reducción en la acumulación de ocratoxina en viñedos

PONSONE M.L; CHIOTTA M. L; NALLY, C; COMBINA M; CHULZE , S.N

Mendoza

Congreso; 37 World Congress of Vine and Wine; 2014

OIV

Argentina ranks among the fourth principal wine producers with excellent organoleptic quality. The wine producing area in our country is principally located in Mendoza and San Juan provinces. In this regions the temperature and humidity conditions are appropriated for Aspergillus section Nigri colonization in grapes. Aspergillus species in section Nigri have been reported as agents of black grape rot. The significance of this disease increased when black Aspergilli, particularly A. carbonarius, were recognized as potential sources of ochratoxin A (OTA) in grapes and wine. OTA is one of the most important mycotoxin of worldwide concern for human and animal health, due to its implication in a diverse range of toxicological effects, including renal toxicity, mutagenicity, teratogenicity and immunotoxicity. This mycotoxin has been classified as a possible human carcinogen (group 2B) by the International Agency for Research on Cancer. Prevention of the growth of OTA-producing fungi is the most effective strategy for controlling the entry of this mycotoxin in the food and feed chains. Biological control has been proposed as a strategy to reduce the impact of ochratoxigenic species in vineyards. This control needs to be used during grape development as a preventive strategy to avoid colonization of the grapes by ochratoxigenic species and, consequently, OTA accumulation. Previous studies carried out in the laboratory described two epiphytic strains of Kluyveromyces thermotolerans that were able to control the growth and OTA accumulation of ochratoxigenic fungi both ?in vitro? and ?in situ?. The data reported until now indicate that the yeasts that occur naturally on grapes, are promising ecological fungicides, because they can survive and colonize grape berries in the vineyards and also maintain the equilibrium of the natural environment. The aim of this study was to evaluate two potential biocontrol agents (Kluyveromyces thermotolerans RCKT4 and RCKT5) in grapevine against Aspergillus section Nigri under field trials during three years. The field assay was performed in a vineyard of Cabernet Sauvignon grapes located in La Rioja province. In this vineyard high incidence of ochratoxigenic Aspergillus was demonstrated in previous studies. The field trial was performed during three consecutive vintages: 2010/2011, 2011/2012 y 2012/2013. The natural occurrence of potentially ochratoxigenic fungi along with the natural occurrence of OTA was evaluated at harvest stage. During (2010/2011) vintage we have no conclusive results since there was a low Aspergillus section Nigri incidence and no ochratoxin A was detected in grapes. During 2011/2012 and 2012/2013 vintages the observed mycoflora showed higher diversity and the OTA accumulation was successfully reduced by the application of the potential biocontrol agents. The OTA reduction content during 2011/2012 vintage was among 50 to 100%, and the most effective doses of biocontrol agent was 106 cel mL-1 in both yeast strains probed (RCKT4 and RCKT5). On the other hand, during 2012/2013 vintage, when it was OTA content reduction in grapes, this reduction was among 60 to 100% in grapes treated with RCKT4 in both inoculum densities (104 y 106 cel mL-1) and in grapes treated with RCKT5 at the highest inoculum density (106 cel mL-1).This results are promissory for the future development of a biopesticide based on native yeasts strains.