Armillaria gallica associated with avocado root rot in Michoacán

Abstract

Aims and background. Root rot and the death of avocado trees related to Armillaria is an emerging disease with a high economic impact in orchards established in previously forested areas of Michoacán. Nowadays, the species related with typical symptoms of wilting, yellowing, excessive fruit production and subcortical mycelia in the roots is unknown. The aim of this investigation was to molecularly characterize the species of Armillaria associated to avocado root rot. Materials and methods. For the morphological and molecular characterization, 60 root simples from trees found in three commercial orchards with a putative presence of Armillaria were processed in a malt-agar extract. The DNA of purified isolations were amplified by PCR with genes RPB2 and TEF α-1. The sequences were aligned using MAFFT and the phylogenies were constructed using the maximum likelihood algorithm in IQ-TREE. Results. Two species were consistently identified: A. gallica (20%) with a 100% homology, and A. mexicana (25%), with 98%. Another species that represented 55% of the isolations was not aligned with any group. Morphologically, the A. gallica basidiocarps coincide with the characteristics of this species. Conclusions. This is the first report on A. gallica associated to avocado root rot in Michoacán.