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Phomopsis husk rot of macadamia in Australia and South Africa caused by novel Diaporthe species |
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| Authors: | Christopher J Wrona Vheena Mohankumar Maritha H Schoeman Yu P Tan Roger G Shivas Olumide S Jeff-Ego Olufemi A Akinsanmi |
| Institution: | 1. The University of Queensland, School of Chemistry and Molecular Biosciences, Brisbane, QLD, Australia
The University of Queensland, Centre for Horticultural Science, Queensland Alliance for Agriculture and Food Innovation, Ecosciences Precinct, Brisbane, QLD, Australia;2. The University of Queensland, Centre for Horticultural Science, Queensland Alliance for Agriculture and Food Innovation, Ecosciences Precinct, Brisbane, QLD, Australia;3. Agricultural Research Council, Tropical and Subtropical Crops, Nelspruit, South Africa;4. Queensland Plant Pathology Herbarium, Department of Agriculture and Fisheries, Ecosciences Precinct, Brisbane, QLD, Australia;5. Queensland Plant Pathology Herbarium, Department of Agriculture and Fisheries, Ecosciences Precinct, Brisbane, QLD, Australia University of Southern Queensland, Centre for Crop Health, Toowoomba, QLD, Australia |
| Abstract: | Phomopsis husk rot (PHR) in macadamia is a disease of economic importance in major commercial production areas in Australia and South Africa. Effective control of PHR is hindered by limited knowledge about its aetiology and epidemiology. The diversity and pathogenicity of more than 50 isolates of Diaporthe associated with PHR in macadamia orchards in Australia and South Africa was assessed. Multilocus phylogenetic analyses of DNA sequences of the ITS, tef1α, and tub2 gene loci revealed four novel clades that are described as Diaporthe australiana sp. nov., D. drenthii sp. nov., D. macadamiae sp. nov., and D. searlei sp. nov. Pathogenicity tests with representative isolates found that all four species caused PHR of varying severity between and within species, as well as between the two macadamia cultivars HAES 344 and HAES 816. The Australian species, D. australiana, was the most aggressive species compared with the three South African species. This study improves our understanding of the aetiology of PHR in macadamia and paves the way for more effective disease management. |
| Keywords: | disease severity fruit pericarp Phomopsis Proteaceae tree nut |