APPLICATION OF VISHNIACOZYMA VICTORIAE AND CALCIUM CHLORIDE FOR THE CONTROL OF POSTHARVEST DISEASES OF PEAR FRUIT UNDER SEMI-COMMERCIAL CONDITIONS.

GORORDO, M.F.; LUCCA; ME; SANGORRIN; MARCELA PAULA

Congreso; LVII SAIB Meeting ? XV SAMIGE Meeting. ISSN; 2021

Biological control agents (BCA) are widely proposed as an alternative of chemical fungicides in order to prevent fungal diseases in organic pear production. Vishniacozyma victoriae NPCC 1263 yeast was previously isolated and selected by our group from the Upper Valley of Río Negro and Neuquén provinces. To obtain high amounts of the selected BCA to be used in semicommercial scale assays it is necessary to scale-up the production process using a low-cost culture medium.The optimized production medium was based on cheese whey powder (CWP): CWP 80 g/L, KH2PO4 10 g/L and (NH4)2SO4 1,2 g/L. Microbial growth was estimated by measuring OD 600 nm, CFU/ml and dried yeast biomass. Yeast biomass production was carried out in a 15 L stirred-tank bioreactor with 12 L of working volume at 20°C and 300 rpm and 0.64 vvm of aeration.The V. victoriae biomass was evaluated through semi-commercial-scale assays in a packaging line of pears, spraying 108 cel/mL with/without CaCl2 (2% w/v) addition over pears Packham´s Triumph (PT, n≈ 1800 per treatment) and Beurrè d´ Anjou pear cultivars (BA, n≈ 400 per treatment). The natural incidence (NI) of Penicillium expansum, Botrytis cinerea, Alternaria sp. and Cladosporium sp. decays was evaluated after 120 and 180 days. Treatments were conserved postharvest in cold rooms (-1/0°C and 95% RH). On the other hand, the fresh biomass grown (UFC/cm2) on pears with different treatment was compared.After 180 days of cold storage, using BA pear cultivars, the V. victoriae with CaCl2 controlled 87% of B. cinerea decay and 72% of P. expansum decay; while reduced the incidence of Alternaria sp. and Cladosporium sp. decays only by 39% and 45%, respectively. On the other hand, the yeasts applied without CaCl2, obtained a similar control percentage at 120 days of cold storage and minor percentage at 180 days for the same disease.During the same cold storage conservation, employed PT pears, V. victoriae with CaCl2 significantly reduced the incidence of P. expansum decays by 55% and 34-38% of Alternaria sp., B. cinerea and Cladosporium sp. decay. Finally, in this variety pear V. victoriae without CaCl2 not shows antagonistic activity, only 17% of control of Cladosporium sp. decay was observed.In this work, the addition of CaCl2 improved the antagonist effect of V. victoriae. This combination revealed the most promising method to control pear decays by four fungal diseases, attaining 34%-87% biocontrol, which is consistent with CaCl2 role as an inducer of fruit defence responses against several pathogens. The simple and easily accessible biomass production medium employed in this work (CWP) ensured the necessary amount of yeasts for scale-up biocontrol testing. The observed reduction in the rate of decay of two pears cultivar by several pathogens achieved by the selected BCA entail a considerable decrease in postharvest economic losses in organic pear production in the North Patagonian region.