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Oral: Fungal Genomics


Genetic basis for pathogenicity in Fusarium oxysporum f.sp. cepae causing basal rot in onion
J. CLARKSON (1), A. Taylor (1), A. Jackson (1), A. Armitage (3), R. Harrison (3) (1) Warwick Crop Centre, University of Warwick, United Kingdom; (2) Warwick Crop Centre, University of Warwick, United Kingdom; (3) East Malling Research, United Kingdom

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Basal rot of onion, caused by Fusarium oxysporum f.sp. cepae (FOC), is a soilborne fungus and part of the F. oxysporum species complex, which includes other important pathogenic formae speciales (f.spp.) adapted to particular crop hosts, as well as non-pathogenic isolates. The genetic basis for pathogenicity in F. oxysporum is poorly understood, but ‘secreted in xylem’ (SIX) genes have recently been associated with virulence in several f.spp. A set of 32 F. oxysporum isolates were tested for pathogenicity on onion and whole genome sequencing and PCR approaches used to detect putative effector genes. Seven SIX genes and two other putative effectors were identified in highly pathogenic isolates which were all absent in non-pathogenic isolates. Expression of SIX genes and other putative effectors increased in planta over 96 hours following inoculation of onion seedlings. Different SIX gene complements were also identified in other f. spp. but none were found in F. avenaceum, F. proliferatum or F. redolens, which have also been associated with basal rot. Preliminary results from a comparative analysis of genomes from pathogenic and non-pathogenic F. oxysporum isolates will also be described as well as the potential use of SIX genes as a diagnostic to enable quantification of FOC and assessment of disease risk in field or store.