Fruit Rot caused by Phytophthora in Cold Storaged Pears in the Valley of Rio Negro and Neuquén, Argentina.

DOBRA, A.;; SOSA, M.C.; GRESLEBIN, A.G.; VELEZ, M.L.; LUTZ, M.C.; RODRÍGUEZ, G.

ACTA HORTICULTURAE

ISHS

Año: 2011

0567-7572

Fruit Rot caused by Phytophthora in Cold Storaged Pears in the Valley of Rio Negro and Neuquén, ArgentinaA.C. Dobra1*, M.C. Sosa1, A.G. Greslebin2, M.L. Vélez2, M.C. Lutz1, and G. Rodriguez11 Facultad de Ciencias Agrarias, Universidad Nacional del Comahue, Ruta Nacional 151, Km 12,5, (8303) Cinco Saltos, Río Negro Patagonia Argentina. Email: aliciadobra53@yahoo.com.ar, mcristinasosa10@gmail.com2 Área de Protección Forestal, Centro de Investigación y Extensión Forestal Andino Patagónico (CIEFAP) Ruta 259 Km. 4, CC 14, 9200 Esquel, Chubut, Argentina. Email: agreslebin@ciefap.org.arKeywords: Phytophthora, postharvest diseases, fruit rot, “Williams”, “Packham`s Triumph”Long periods of pear fruit conservation are associated with postharvest fungal diseases. In Argentina, the most important and widespread diseases are caused by Botrytis cinerea and Penicillium spp., followed by Alternaria sp. and Cladosporium sp. Sporadically Athelia epiphylla can be important associated to fruit-lot. This study reports the presence and incidence of one Oomycete, as causal of pear fruit rots in postharvest. In 2010, during the first months of conservation of pear fruits “Williams”, “Packham`s Triumph” and “Red Bartlet” cv., in cold storages placed in the eastern area of the Rio Negro high valley one rot was recorded with fruit losses between 5 and 20%, according to lot. Symptoms of rot were studied and its ethiology was determined using conventional and molecular methods. Fruits started showing circular, light to dark brown areas with irregular and diffuse margins that spreadrapidly. The rotted area was firm and lesion diameter increased and it extended to pulp tissue to achieve fruit core with a hyperbolic shape, different from the espheric shade caused by Penicillium spp. or Botrytis sp. The pathogen was isolated in V8 agar selective medium from pear fruit with symptoms. By morphologic characteristics (colony and sporangia) of isolates its association with clade 6 of Phytophthora was determined. The identification of isolates was confirmed by direct sequencing of the ITS rDNA region using DC6 and ITS4 primers. The nucleotide sequence showed 100% of similarity (745/745pb) with sequences available in GenBank and was identified as an undescribed species into P. gonapodyides-P. megasperma Clade 6. This is the first report of a new Phytophthora in postharvest pear fruits.