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Inoculum dynamics and infection of citrus fruit by Phyllosticta citricarpa

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Tran, N. T., Miles, A., Dietzgen, R. G., Shuey, T. A., Mudge, S. R., Papacek, D., Chandra, K. A. and Drenth, A. (2020) Inoculum dynamics and infection of citrus fruit by Phyllosticta citricarpa. Phytopathology (ja). null.

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Article Link(s): https://doi.org/10.1094/PHYTO-02-20-0047-R

Publisher URL: https://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO-02-20-0047-R


Citrus black spot caused by Phyllosticta citricarpa is characterized by fruit blemishes and premature fruit drop, resulting in significant economic losses in summer rainfall areas. The pathogen forms both conidia and ascospores during its life cycle. However, the occurrence of these spores and their contributions to infection of fruit in field conditions are not well-understood. Our research using direct leaf litter monitoring and volumetric spore trapping in Queensland orchards revealed that pseudothecia and ascospores in leaf litter, as well as trapped ascospores had low abundance, while pycnidia and conidia were highly abundant. Both P. citricarpa and endophytic Phyllosticta spp. were identified, with P. citricarpa being dominant. In replicated field trials we determined that infection of ‘Imperial’ mandarin fruit by P. citricarpa occurred from fruit set until week 20 of fruit development, with the key infection events taking place between weeks 4 and 16 in Queensland subtropical conditions. These results demonstrate that protecting fruit during weeks 4 to 16 significantly reduced P. citricarpa infection. We found no significant correlation between the disease incidence in fruit and P. citricarpa conidial abundance in leaf litter, or ascospore abundance measured by volumetric spore trapping. It is therefore suggested that inoculum sources in the tree canopy other than those detected by spore trapping and direct leaf litter monitoring may play a major role in the epidemiology of citrus black spot. The improved knowledge on epidemiology of P. citricarpa and an understanding of propagules causing infection may aid in development of more effective disease management strategies.

Item Type:Article
Business groups:Horticulture and Forestry Science
Keywords:Ecology and epidemiology
Subjects:Plant culture > Food crops
Plant culture > Fruit and fruit culture
Plant pests and diseases > Plant pathology
Deposited On:28 May 2020 04:31
Last Modified:28 May 2020 04:31

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