Botryosphaericeae and Diaporthaceae species associated with blueberry plants in Portugal

• Autor(a) principal: Hilário, Sandra Cristina Carvalho
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/21454
• topic: Mirtilos; Vaccinium corymbosum; Doenças das plantas

The blueberry (Vaccinium corymbosum) is a non-native and increasingly cultivated plant in Portugal and represents an important part of the economy of some regions. The rapid growing of blueberry production has been accompanied by an increase of diseases caused by plant pathogens, mainly fungi. However, there is an overall lack of studies concerning blueberry fungal pathogens occurring in Portugal. This study aimed to contribute to fill this gap by focusing on Diaporthaceae and Botryosphaeriaceae species, which are known pathogens affecting cultivated areas of blueberry worldwide. For this, a collection of 222 fungal isolates obtained from blueberry plants, including asymptomatic and symptomatic, was characterised. All 222 isolates were initially subjected to BOX-PCR fingerprinting to evaluate their overall genetic diversity. From the cluster analysis performed on BOX-PCR fingerprints 81 isolates representative of each cluster were selected for molecular identification, namely by ITS sequencing and analysis. A primary identification based on ITS sequences allowed identifying 13 different genera with Neofusicoccum and Botryosphaeria (Botryosphaeriacaeae) and Diaporthe (Diaporthaceae) being the most common. The isolates identified by ITS sequences as members of Diaporthe, Neofusicoccum and Botryosphaeria were further subjected to multi locus sequence analyses in order to correctly identify them to the species level. Thus, sequences of the translation elongation factor 1-alpha (tef1-α) were obtained for Neofusicoccum and Botryosphaeria isolates. β-tubulin (tub), tef1-α, histone (his), and calmodulin (cal) were also used for multi locus sequence analysis of Diaporthe species. Combined ITS and tef1-α phylogenetic analyses showed that all Botryosphaeria isolates belonged to the species B. dothidea, while Neofusicoccum isolates belonged to three different species, namely N. australe, N. eucalyptorum and N. parvum. Neofusicoccum parvum was the most abundant of all Botryosphaeriacaeae species found. Phylogenetic analyses placed the Diaporthe isolates into distinct clades representing three known species (D. eres, D. foeniculina, and D. rudis) and three putative novel species (Diaporthe sp.1, Diaporthe sp.2, and Diaporthe sp.3), with D. eres and Diaporthe sp. 2 being the most abundant. The putative novel species were fully characterised in terms of morphology, ability to grow at different temperatures and their mating types. Full taxonomic descriptions are given for all of them. Pathogenicity tests using isolates representative of each species showed that all Diaporthe, Neofusicoccum and Botryosphaeria were pathogenic to blueberry plants of the cultivar Bluecrop. Among the Botryosphaeriacaeae species, N. parvum was the most aggressive while Diaporthe sp. 3 was the most aggressive of all Diaporthe species tested. Neofusicoccum parvum was the only species the induced plant death and it is thus regarded as probably the most relevant pathogen of blueberry. This study represents the first confirmation of the occurrence in Portugal of D. eres, D. foeniculina, D. rudis, N. australe, N. parvum and B. dothidea on blueberries. Additionally, N. eucalyptorum, a common Eucalyptus spp. pathogen, is reported worldwide for the first time as a pathogen of blueberry. This represents a relevant host jump whose potential future implications on blueberry plantations are not understood. The results presented show that species of Diaporthe and Botryosphaeriacaeae are common on blueberry plantations in Portugal. Their diversity throughout the country and pathogenicity towards other blueberry cultivars deserve further studies.