Plant Disease (2018) 102, 1386-1393

Nga T. Tran, Andrew K. Miles, Malcolm W. Smith, Ralf G. Dietzgen and André Drenth (2018)
Pathogenicity of Phyllosticta citricarpa ascospores on Citrus spp.
Plant Disease 102 (7), 1386-1393
Abstract: Citrus black spot, caused by Phyllosticta citricarpa, is one of the most important fungal diseases in many citrus-growing regions with hot and humid summers. Ascospores and conidia are known to contribute to epidemic development of the disease. However, pathogenicity testing has never been done for pure ascospores produced from fully characterized P. citricarpa isolates, due to the inability to induce the sexual state in vitro. Recently, an in vitro mating technique was developed to readily produce pure P. citricarpa ascospores for use in host inoculation studies. To test the pathogenicity of P. citricarpa ascospores, we inoculated Troyer citrange leaves and Murcott tangor fruit with ascospores produced in vitro from characterized P. citricarpa isolates. Typical symptoms of citrus black spot occurred. Recovery of P. citricarpa isolates from symptomatic lesions and their characterization using genetic markers enabled us to identify recombinant genotypes among the isolates recovered from ascospore inoculations and, as such, fulfill Koch's postulates for ascospores. We have also identified Troyer citrange seedlings as a potential model system for citrus black spot inoculation studies, because it allows typical symptoms of citrus black spot to be expressed with a much shorter latent period than on fruit. This will facilitate future studies of epidemiological aspects of P. citricarpa ascospores relative to conidia and improve our understanding of the citrus black spot pathosystem. The susceptibility of Troyer citrange seedlings will also facilitate experimenting with disease management methods, aimed at reducing the impact of citrus black spot.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Andre Drenth

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Phyllosticta citricarpa	Citrus (genus)