Combination of control strategies for inhibition of Penicillium expansum, table grapes pathogen

PEDROZO L.P.; FLORES C.B.; LLADÓ C.; RODRIGUEZ ASSAF L.A.; PESCE V.M.; MATURANO Y.P.; NALLY M.C; VAZQUEZ F.

Congreso; XLI REUNIÓN CIENTÍFICA ANUAL DE LA SOCIEDAD DE BIOLOGÍA DE CUYO; 2023

Food loss due to post-harvest fungal contamination presents numerous challenges for the agri-food industry in relation to sustainability andfood safety. Table grape is a highly perishable, non-climacteric fruit and despite its conservation at low temperatures, it can suffer infectionfrom phytopathogenic fungi, such as Penicillium expansum (Eurotiomycetes, Ascomycota), causal agent of blue rot. This postharvestpathogen, can cause significant losses in this fruit, presents risks associated with a mycotoxin production known as patulin. Given thatfrequent chemical control can cause the selection of resistant fungal populations, added to the market demand for sustainable production, thesearch for new alternatives is needed to control the development of blue rot, in refrigerated environments (2±1 °C). The aim of this work,was to evaluate the combined use of wine yeasts of Metschnikowia pulcherrima (Mp22, Mp36, Mp43) previously selected for inhibiting thegrowth of P. expansum, with sodium bicarbonate (NaHCO3) as a GRAS substance (Generally Known As Safe). These factors were optimizedto improve the inhibition of conidia germination (ICG) and the decrease in germ tube length (GTL) of P. expansum at 2±1 °C. To optimizethe combination of 3 native yeasts and NaHCO3, a Box-Behnken experimental design with 4 factors, 3 levels and 29 experimental runs, wasapplied and statistical analysis of Response Surface Methodology (RSM) was generated with Stat-Ease software Design-Expert 11. ANOVAwas carried out to estimate statistically significant factors and the quality of the model equation was expressed as R2. In microtubes of 2 mLcapacity, treatments were prepared with a suspension of yeasts at different concentrations according to the experimental design (100μL; 0cell/mL-1, 5x107 cell/mL-1, 1x108 cell/ mL-1), conidia of P. expansum (100μL; 104 conidia.mL-1) and diluted grape must (shortage of nutrients),(800 μL; 1% v/v), added with NaHCO3 ( 0, 0.25 and 0.50 % w/v). For control treatments, NaHCO3 or yeasts were replaced with steriledistilled water. The germinated conidia were counted and the GTL was measured with Image J imaging software after 7 days of incubationat 2 ± 1 °C. Conidia were considered germinated when the GTL reached or exceeded the conidia diameter. Results were expressed aspercentage and the GTL was expressed in micrometers. For GTL response variable a reduced quadratic model was found (p=0.0008; R2=0.5354) where NaHCO3 (p=0.0029) significantly decreased the GTL in combination with Mp36 yeast. The evaluation of ICG showed aquadratic model as significant (p-value=0.0031; R2= 0.4194). NaHCO3 improved the ICG when the yeast Mp36 was included in the RSManalysis. The data found would indicate that the use of biocontrol yeasts and NaHCO3 is compatible to optimize the control of the conidiagermination of P. expansum through the application of experimental design and the evaluation of RSM.