A multi-gene phylogeny for species of Mycosphaerella occurring on Eucalyptus leaves

Abstract

Species of the ascomycete genus Mycosphaerella are regarded as some of the most destructive leaf pathogens of a large number of economically important crop plants. Amongst these, approximately 60 Mycosphaerella spp. have been identified from various Eucalyptus spp. where they cause leaf diseases collectively known as Mycosphaerella Leaf Disease (MLD). Species concepts for this group of fungi remain confused, and hence their species identification is notoriously difficult. Thus, the introduction of DNA sequence comparisons has become the definitive characteristic used to distinguish species of Mycosphaerella. Sequences of the Internal Transcribed Spacer (ITS) region of the ribosomal RNA operon have most commonly been used to consider species boundaries in Mycosphaerella. However, sequences for this gene region do not always provide sufficient resolution for cryptic taxa. The aim of this study was, therefore, to use DNA sequences for three loci, ITS, Elongation factor 1-alpha (EF-1α) and Actin (ACT) to reconsider species boundaries for Mycosphaerella spp. from Eucalyptus. A further aim was to study the anamorph concepts and resolve the deeper nodes of Mycosphaerella, for which part of the Large Subunit (LSU) of the nuclear rRNA operon was sequenced. The ITS and EF-1α gene regions were found to be useful, but the ACT gene region did not provide species-level resolution in Mycosphaerella. A phylogeny of the combined DNA datasets showed that species of Mycosphaerella from Eucalyptus cluster in two distinct groups, which might ultimately represent discrete genera.

Species of Mycosphaerellaceae and Teratosphaeriaceae on native Myrtaceae in Uruguay: evidence of fungal host jumps

“…Mycosphaerella aurantia) was found associated with leaf spots on Blepharocalyx salicifolius. Although there has been some confusion regarding the identification of this species, with Hunter et al (2006) suggesting that it is likely the same as Teratosphaeria africana, isolate UY1382 obtained from Blepharocalyx salicifolius grouped strongly with other T. aurantia isolates, including that of the ex-type (Maxwell et al 2003). Morphological characteristics of ascospores observed in this study also showed they did not have constrictions at the median septum, as described for T. aurantia (Maxwell et al 2003).…”

“…Mycosphaerella heimii) (Crous et al, 2013). Although Hunter et al (2006) considered Pal. heimii to represent a member of a species complex due to the difficulty differentiating this species from Pal.…”

“…Mycosphaerella leaf diseases (MLD), which are considered particularly important in Eucalyptus plantations worldwide (Cortinas et al 2006;Crous et al 2004;Crous et al 2006;Crous et al 2009;Maxwell et al 2003;Hunter et al 2006;Hunter et al 2011;Park et al 2000;Perez et al 2009a;Summerell et al 2006). These fungi cause leaf spots, leaf blotches, or petiole and stem cankers that often result in stressed and stunted trees, adversely affecting commercial forestry operations (Carnegie et al 1994;Carnegie et al 1998;Lundquist and Purnell 1987;Park et al 2000;Sanchez Marquez et al 2011).…”

Endophyte isolations from Syzygium cordatum and a Eucalyptus clone (Myrtaceae) reveal new host and geographical reports for the Mycosphaerellaceae and Teratosphaeriaceae

“…Morphological identification is difficult for species of the Mycosphaerellaceae and the Teratosphaeriaceae because they typically grow slowly in culture and many also sporulate only on host tissue (Crous 1998;Crous et al 2001a;Hunter et al 2004Hunter et al , 2006. Where morphology can be used for identification, it is based on the associated but morphologically variable anamorph genera (Crous 1998;Crous et al 2001a;Hunter et al 2004).…”

“…This group of fungi included approximately 3,000 species names with diverse ecological roles representing endophytes, pathogens and saprobes (Corlett 1995;Crous et al 2000;Hunter et al 2004Hunter et al , 2006Crous et al 2009c;Hunter et al 2011). The pathogens in these genera include important leaf and shoot pathogens of a number of hosts, including Eucalyptus and other trees in the Myrtaceae.…”