First report of avocado tree wilt by Pythium sp. amazonianum in Mexico

Abstract

Yisa M. Ochoa Fuentes, A. Hernández Pérez, J.C. Delgado Ortiz, M. Beltran Beache,

L.M. Tapia Vargas, O. Hernández Bautista, and E. Cerna Chavez. 2018. First report of

avocado tree wilt by Pythium sp. amazonianum in Mexico. Cien. Inv. Agr. 45(3): 301-305.

In August and September 2014, different avocado orchards (Persea americana Mill. Var. Hass)

were sampled in four municipalities (Tancítaro, Uruapan, San Juan Nuevo Parangaricutiro and

Peribán) of the “Franja aguacatera” in Michoacan State, Mexico. Samples were collected from

avocado trees showing symptoms of the “Tristeza del aguacate” disease. Strains of Pythium

sp. were obtained consistently from symptomatic tissue isolated in the selective medium V8®-

Agar-PARPH. Morphological identification was made through taxonomic keys, and molecular

identification was obtained by sequencing Internal Transcribed Spacer (ITS) gene. Koch’s

postulates were corroborated by pathogenicity tests carried out on P. americana seedlings with

six true leaves, identifying the strain of P. sp. amazonianum as the causal agent of the “Tristeza

del aguacate” disease. This is the first report that associates the “Tristeza del aguacate” with P.

sp. amazonianum in Michoacan, Mexico.