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Species of the Botryosphaeriaceae are important pathogens causing cankers and die-back on many woody plants. In Uruguay, Neofusicoccum eucalyptorum, N. ribis and B. dothidea have previously been associated with stem cankers on plantation-grown Eucalyptus globulus. However, very little is known regarding the occurrence and species diversity of Botryosphaeriaceae in native Myrtaceae forests or what their relationship is to those species infecting Eucalyptus in plantations. The objectives of this study were to identify the Botryosphaeriaceae species present as endophytes or associated with cankers in both introduced and native tree hosts in Uruguay, and to test the pathogenicity of selected isolates obtained from native trees on Eucalyptus. Symptomatic and asymptomatic material was collected countrywide from Eucalyptus plantations and native Myrtaceae trees. Single spore cultures were identified based on conidial morphology and comparisons of DNA sequences of the ITS and EF1-α regions. Six Botryosphaeriaceae species were identified. Botryosphaeria dothidea, N. eucalyptorum and specimens residing in the N. parvum-N. ribis complex were isolated from both introduced Eucalyptus and native Myrtaceae trees, whereas Lasiodiplodia pseudotheobromae was found only on Myrcianthes pungens. Diplodia pseudoseriata sp. nov. and Spencermartinsia uruguayensis sp. nov. are novel species found only on native myrtaceous hosts. Pathogenicity tests showed that isolates obtained from native trees and identified as L. pseudotheobromae, N. eucalyptorum and the N. parvum-N.ribis complex are pathogenic to E. grandis. Interestingly, Lasiodiplodia pseudotheobromae has not previously been found on Eucalyptus in Uruguay and represents a potential threat to this host.

Serratia marcescens is a Gram-negative bacterial species that can be found in a wide range of environments like soil, water and plant surfaces, while it is also known as an opportunistic human pathogen in hospitals and as a plant growth promoting bacteria (PGPR) in crops. We have used a pangenome-based approach, based on publicly available genomes, to apply whole genome multilocus sequence type schemes to assess whether there is an association between source and genotype, aiming at differentiating between isolates from nosocomial sources and the environment, and between strains reported as PGPR from other environmental strains. Most genomes from a nosocomial setting and environmental origin could be assigned to the proposed nosocomial or environmental MLSTs, which is indicative of an association between source and genotype. The fact that a few genomes from a nosocomial source showed an environmental MLST suggests that a minority of nosocomial strains have recently derived from the environment. PGPR strains were assigned to different environmental types and clades but only one clade comprised strains accumulating a low number of known virulence and antibiotic resistance determinants and was exclusively from environmental sources. This clade is envisaged as a group of promissory MLSTs for selecting prospective PGPR strains.

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Neofusicoccum eucalyptorum is a canker-associated fungus apparently highly specialized on Eucalyptus. However, in surveys of the microbial population inhabiting native Myrtaceae in Uruguay, fungal cultures resembling N. eucalyptorum were isolated. The possible occurrence of N. eucalyptorum on hosts other than Eucalyptus prompted further investigation. Several surveys were conducted throughout Uruguay to obtain samples from native forests, focusing primarily on species in the Myrtaceae. Fungal identification was based on morphology and confirmed using comparison sequences for the internal transcribed spacer (ITS) of the rDNA operon. Pathogenicity was evaluated by inoculating plants of a Eucalyptus grandis clone. Morphological and molecular identification confirmed the occurrence of N. eucalyptorum on Blepharocalyx salicifolius, Myrceugenia glaucescens and Myrrhinium atropurpureum var. octandrum. This is the first report of N. eucalyptorum occurring in hosts other than Eucalyptus. Pathogenicity tests confirmed the ability of this species to produce cankers on E. grandis. This study provides information that will assist breeding programmes in attempts to obtain disease-resistant Eucalyptus plantations and it also suggests that a Eucalyptus pathogen could have moved to native trees in Uruguay.