Phytophthora cinnamomi Rands. Pathogenicity tests in Pseudotsuga mensiezii

Abstract

Phytophthora cinnamomi Rands is a soil microorganism that has caused large economic and environmental losses worldwide in a wide array of hosts. For this reason, P. cinnamomi was identified and its pathogenicity was evaluated in five isolations from five different regions in Mexico on Pseudotsuga mensiezii plants. The isolations were taken from the soil, roots, and cankers of Quercus salicifolia trees, from El Arrayanal, Col. (COL-A); Quercus elliptica from Tecoanapa, Gro. (GRO-P), Quercus peduncularis from Manántlan, Jal. (JAL-C), Pseudotsuga mensiezii from Edo. de México (EDO-T), and Persea americana, from Peribán Mich. (MICH-P). Through a morphological analysis on genus and molecular analysis on species (accession number: KP773290, KP773291, KP773292, KP773293, KP773294) the identification of the isolations was corroborated with the molecular analyses that indicate a homology of 99 % identity with P. cinnamomi. Pathogenicity was tested on healthy three year old P. menziesii plants. Five plants were used for each isolation with its respective control of five uninoculated plants; the plants were kept under greenhouse conditions and the observations of symptoms were carried out weekly for eight months. The results obtained indicated that the five P. cinnamomi plants are capable of infecting the P. menziesii plants.

The isolation COL-A, from the area of Arrayanal Col. Behaved as the most pathogenic, causing the death, in the shortest period, of the plants after 120 ddi, followed by the isolations GRO-P at 180 ddi, JAL-C and EDO-T at 210 ddi, and MICH-P at 240 ddi. The data obtained in the test was analyzed with the Kruskall-Wallis test, finding significant differences of the isolations on the host. The control presented no symptoms. This is the first report on P. cinnamomi isolated from Q. salicifolia, Q.elliptica, Q.peduncularis, P. mensiezii, and P. americana evaluated in P. mensiezii plants, where the pathogenicty of the pathogen is corroborated.