CONICET | Buscador de Institutos y Recursos Humanos

In 2013-2014, economic losses by decay in "Packham´s Triumph" pears were recorded in a packinghouse of the Alto Valle de Río Negro. Fruit had been treated against Penicillium spp. and Botrytis cinerea with captan and pyrimethanil, and stored into carton packets with nylon in controlled atmosphere. After 9 months, 64 packets with 5500 fruits corresponding to seven different lots were evaluated. Severe symptoms of decay on fruit were observed. The losses were quantified and the etiology of the disease studied. By observation of symptoms and microscopy, Botrytis cinerea and Phytophthora sp. were identified. Koch Postulates and inoculation of single or combined pathogens in fruit were performed. Affected fruit came from orchards of two production´s zones of Rio Negro and Neuquén. Incidence percentage of this decay (% DI) in all fruit reached 13%. The most affected lots showed %DI distributed: (i) 1.3 - 3% of B. cinerea; (ii) 0.5 - 1.2% of B. cinerea and Phytophthora sp. and (iii) 1.2 - 1.6% of Phytophthora sp.. The fruit decay of the combined pathogens was firm to touch, practically mummified, with two distinct brown colorations, diffuse water soaked margins, and without formation of B. cinerea nests. Cultures of B. cinerea in APD-N and Phytophthora sp. in V-8 media showed typical characteristics of each pathogen. In laboratory, detection of Phytophthora in samples of orchard´s soil with pear baits was verified. Since post-harvest diseases are a combination of latent infections settled during the growing season and post-harvest wounds, asymptomatic fruit taken 30d prior to harvest and at physiological ripeness was processed with ONFIT (overnight freezing incubation technique) detecting 5 and 2% of Phytophthora and 0-2% of B. cinerea. This is the first report for the region of post-harvest pear fruit decay caused by B. cinerea associated to Phytophthora sp. with detection of latent infections.