Submitted to: Persoonia: Molecular Phylogeny and Evolution of Fungi
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2013
Publication Date: 2/25/2014
Citation: Udayanga, D., Castlebury, L.A., Rossman, A.Y., Hyde, K.D. 2014. Species limits in Diaporthe: molecular re-assessment of D. citri, D. foeniculina and D. rudis with a new species on Citrus. Persoonia: Molecular Phylogeny and Evolution of Fungi. 32(1):83-101. Interpretive Summary: Fungi cause billions of dollars damage to agricultural crops each year. A disease of oranges and other citrus crops called melanose or stem end rot is caused by a fungus that has been confused with fungi on other hosts. In this research similar fungi on citrus crops from around the world were analyzed based on molecular data in order to determine which fungal pathogens occur in the United States. It was determined that three different species of this fungal group occur on citrus in the United States. One of these is a species new to science that is known only from California and Spain. This new species is named, described and illustrated. Another fungal species occurs only on citrus throughout the world. A third fungal species that occurs on citrus is also found on other woody host plants. This research will be used by plant breeders who are working to develop oranges and other citrus crops that are resistant to this disease. In addition it provides the basis for preventing the spread of these fungal diseases on citrus.
Technical Abstract: Species of Diaporthe are important plant pathogens associated with a wide range of hosts throughout the world. In the present study, the species causing melanose and stem end rot diseases on Citrus spp. were revised. Morphology and molecular phylogenetic analyses of the complete nuclear ribosomal internal transcribed spacer regions and partial sequences of actin, beta-tubulin, calmodulin, and translation elongation factor 1-alpha were used to resolve the species relationships and boundaries of species of Diaporthe. Three species of Diaporthe were found to be associated with Citrus. Diaporthe citri occurs on Citrus throughout the Citrus-growing regions of the world. A novel species Diaporthe fawcettii is described and illustrated based on recent cultures from Citrus sinensis in California. Diaporthe foeniculina, including the synonym D. neotheicola, is recognized as a species with an extensive host range including Citrus. Diaporthe medusaea, a name widely used for D. citri, was determined to be a synonym of D. rudis, a species with a broad host range. Diaporthe citri, D. foeniculina, and D. rudis are epitypified, described and illustrated with a review of all potential synonyms based on molecular data and morphological studies. Newly designed primers are introduced to optimize the amplification and sequencing of calmodulin and actin genes in Diaporthe.