Phakopsora myrtacearum sp. nov., a newly described rust (Pucciniales) on eucalypts in eastern and southern Africa

Abstract

Outbreaks of a rust disease in eucalypt forestry plantations and nurseries in Kenya, Mozambique and South Africa occurred between 2009 and 2014. The pathogen was identified using morphology and molecular phylogenetic analyses as an undescribed species in the Phakopsoraceae. A systematic study, based on nuclear ribosomal DNA, showed that it is a species of Phakopsora, herein named Phakopsora myrtacearum sp. nov. This new species of rust is the second validly described species on Eucalyptus, along with Puccinia psidii. Phakopsora myrtacearum is distinguished from P. psidii by leaf symptoms, morphology of the urediniospores and distinct phylogenetic placement. Phakopsora myrtacearum has been found on three species of Eucalyptus in Kenya, Mozambique and South Africa, and it may have future negative implications for commercial forestry in these areas.

Rust (Puccinia psidii) recorded in Indonesia poses a threat to forests and forestry in South-East Asia

“…The present study recovered P. psidii sister to Dasyspora within the Sphaerophragmiaceae, sister to the Pucciniaceae, a relationship that was previously shown by Maier et al (2015) and Beenken and Wood (2015). Puccinioid spores are a homoplasious character within the Pucciniales (Beenken and Wood 2015).…”

“…New disease reports from countries with susceptible hosts are eliminated as potential sources, as the rust would be expected to occur there already. Previous studies have indicated that the origin of P. psidii may be from a location with shared plants in the Annonaceae and Myrtaceae (Maier et al 2015)..…”

“…The rapid, global spread of P. psidii is of concern and illustrates the ease with which tree pests and pathogens move (Wingfield et al 2015). Pathways of spread differ depending on the ecology of the organisms involved.…”

“…The mitotic, uredinial stage produces masses of yellow urediniospores that defoliate juvenile trees, cause severe stem and foliage blight, and can affect developing fruits and inflorescences (Pegg et al 2014). The symptoms produced by the uredinia of P. psidii are characteristic and useful to distinguish it from other rusts on Myrtaceae, such as Phakopsora myrtacearum (Maier et al 2015). A study on the lifecycle of P. psidii could not conclusively determine the function of the meiotic, telial stage, and indicated that populations of P. psidii are clonal and spread by uredinia (Morin et al 2014).…”

“…Puccinia psidii, rusts on Myrtaceae, and members of the Sphaerophragmiaceae that have an affinity with P. psidii (Beenken and Wood 2015;Maier et al 2015) were Doungsa-ard et al (2015) included in the analyses (Table 1). The LSU region of all taxa was aligned with the MAFFT algorithm (Katoh et al 2009) in SATe (Liu et al 2012), and run under two phylogenetic criteria, Bayesian inference and maximum likelihood.…”