RESUMEN
Neofusicoccum parvum and N. ribis are closely related species whose identities often have been confused. These fungal plant pathogens were identified recently as the most abundant species of Botryosphaeriaceae (Ascomycetes) isolated from native Syzygium cordatum trees in South Africa. In another study using multiple gene genealogies from five nuclear loci three undescribed cryptic phylogenetic species as well as N. parvum were identified among 30 of these isolates. The aim of this study was to clarify the identity of the remaining isolates in the N. parvum/N. ribis complex from S. cordatum in South Africa, to describe newly identified cryptic species and to test their pathogenicity. Based on the RNA polymerase II subunit (RPB2) sequence comparisons, the isolates were identified as N. parvum or one of three previously recognized phylogenetic species that are described here as N. cordaticola, N. kwambonambiense and N. umdonicola. These species cannot be separated a priori based on morphological characteristics, although a posteriori analysis of variance showed that the differences in conidial length and width between the species were statistically significant. The isolates of the newly described species as well as N. parvum and N. ribis were tested for pathogenicity on S. cordatum under greenhouse conditions. Isolates representing the three new species were significantly more aggressive than N. parvum and N. ribis with N. kwambonambiense being the most aggressive. This study resolved long-standing questions of identity of species within N. parvum/N. ribis complex and lays a foundation for further studies on this group of pathogens.
Asunto(s)
Ascomicetos/clasificación , Ascomicetos/patogenicidad , Myrtaceae/microbiología , Filogenia , Enfermedades de las Plantas/microbiología , Ascomicetos/genética , Ascomicetos/fisiología , ADN de Hongos/análisis , Datos de Secuencia Molecular , Técnicas de Tipificación Micológica , Fenotipo , ARN Polimerasa II/genética , Análisis de Secuencia de ADN , Sudáfrica , Especificidad de la EspecieRESUMEN
Neofusicoccum parvum and N. ribis (Botryosphaeriaceae, Ascomycetes) are closely related, plant pathogenic fungi with a world-wide distribution on a wide range of woody hosts. Species boundaries in the N. parvum/N. ribis complex have eluded definition, despite the application of various tools for characterisation. In this study, we test the hypothesis that only one species exists amongst isolates from the N. parvum/N. ribis complex, identified from Syzygiumcordatum trees across their native distribution in South Africa. Genealogical concordance phylogenetic species recognition (GCPSR) was applied based on concordance of genealogies obtained from DNA sequence data for five nuclear loci. These data showed that the single species hypothesis must be rejected. Rather, all analyses support the existence of three previously unrecognised, cryptic species within the N. parvum/N.ribis complex from S. cordatum, in addition to N. parvum and N. ribis. The three lineages reflecting these cryptic taxa are sympatric across their geographical range, indicating barriers to gene flow other than geographic isolation. Phenotypic characters failed to detect all the species uncovered by the GCPSR. Sequence data of the Internal Transcribed Spacer (ITS) of the ribosomal DNA locus, which is thought to be useful for barcoding in fungi, did not distinguish all the species with confidence. RNA polymerase II subunit (RPB2) was the most informative to distinguish all the species a posteriori to the application of GCPSR. The results reflect the critical importance of using multiple gene genealogies and adequate sampling to identify cryptic species and to characterise the true diversity within the Botryosphaeriaceae.
Asunto(s)
Ascomicetos/genética , Evolución Molecular , Especiación Genética , Filogenia , Ascomicetos/clasificación , Ascomicetos/fisiología , ADN de Hongos/genética , ADN Espaciador Ribosómico/genética , Flujo Génico , Genes Fúngicos , Geografía , Polimorfismo de Nucleótido Simple , Alineación de Secuencia , Análisis de Secuencia de ADN , Sudáfrica , Especificidad de la EspecieRESUMEN
In this study seven new species of the Botryosphaeriaceae are described from baobab (Adansonia gibbosa) and surrounding endemic tree species growing in the Kimberley region of northwestern Australia. Members of the Botryosphaeriaceae were predominantly endophytes isolated from apparently healthy sapwood and bark of endemic trees; others were isolated from dying branches. Phylogenetic analyses of ITS and EF1-alpha sequence data revealed seven new species: Dothiorella longicollis, Fusicoccum ramosum, Lasiodiplodia margaritacea, Neoscytalidium novaehollandiae, Pseudofusicoccum adansoniae, P. ardesiacum and P. kimberleyense.