Description of the demicyclic life cycle of Puccinia sherardiana in Sphaeralcea angustifolia in Mexico.

Abstract

During 2017 and 2018, plants with dark brown lesions containing hypophilic telia surrounded by chlorotic halos were collected on leaves and stems of Sphaeralcea angustifolia located in Axapusco, Estado de México. Based on the morphological characteristics of pycnia, aecia and telia observed in light microscopy and scanning electron microscopy, the fungus Puccinia sherardiana was identified. No uredinal status was present during the observation period. Verification of identity was performed by phylogenetic analysis with a ribosomal DNA 28S gene sequence. Additionally, pathogenicity tests were performed on leaves of S. angustifolia by inoculation of teliospores. The inoculated plants developed symptoms 15 days after inoculation, beginning with the presence of errupent aecia in the epidermis of the host and later telia were formed, completing Koch's Postulates. Puccinia sherardiana was previously described as a rust with a microcyclic life cycle on species of the genera Alcea, Malvastrum, Sidalcea and Sphaeralcea, belonging to the Malvaceae family, however, this study showed that this phytopathogenic fungus has a demicyclic life cycle.