Abstract:
Mycosphaerella species are well-known causal agents of leaf diseases on many economically
and ecologically important plant species. In Uruguay, a relatively large number of Mycosphaerellaceae
and Teratosphaeriaceae are found on Eucalyptus, but nothing is known of
these fungi on native Myrtaceae. The aim of this study was to identify Mycosphaerellaceae
and Teratosphaeriaceae species associated with leaf diseases on native Myrtaceae in Uruguay
and to consider whether host jumps by the pathogen from introduced Eucalyptus to
native Myrtaceae have occurred. Several native forests throughout the country were surveyed
with special attention given to those located close to Eucalyptus plantations. Five species
belonging to the Mycosphaerellaceae and Teratosphaeriaceae clades were found on
native Myrtaceous trees and three of these had previously been reported on Eucalyptus in
Uruguay. Those occurring both on Eucalyptus and native Myrtaceae included Pallidocercospora
heimii, Pseudocercospora norchiensis, and Teratosphaeria aurantia. In addition, Mycosphaerella
yunnanensis, a species known to occur on Eucalyptus but not previously recorded
in Uruguay, was found on leaves of two native Myrtaceous hosts. Because most of these
species occur on Eucalyptus in countries other than Uruguay, it appears that they were introduced
in this country and have adapted to be able to infect native Myrtaceae. These apparent
host jumps have the potential to result in serious disease problems and they should
be carefully monitored.
