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Contribution of Fusarium spp. to sugarcane yellow canopy syndrome (YCS) in Australia

Shiromi Basnayake: Queensland Alliance for Agriculture and Food Innovation (QAAFI)

<div>Yellow canopy syndrome (YCS) of sugarcane, first discovered in North Queensland, Australia, is characterized by prematurely senescing, bright orange leaves in the lower canopy of the plant. Spread of this disorder from northern to southern Queensland and northern New South Wales suggests that this is biotic in nature, although symptoms are likely to be modulated by abiotic stresses. Previous research has shown accumulation of starch in early senescing leaves and also disruption of vascular transport, similar to other well-characterized diseases caused by bacteria and viruses. In order to provide clues as to the aetiology of the disease, a range of antimicrobial agents [streptomycin and oxytetracycline (antibiotics), metalaxyl (systemic fungicide) and prochloraz (general fungicide)] were tested on the sugarcane variety Q200 in field trials established in ‘YCS hotspots’ in Ingham and the Burdekin region in the 2016/17 season. Treatments had no negative effect on crop physiology or growth. Delay in symptom development was observed only in the plants treated with streptomycin. To search for evidence of pathogen infection, vascular regions of plants from the various treatments were examined by light microscopy and a range of fungal and bacterial structures observed mainly in symptomatic leaves. Several <em>Fusarium</em> isolates were obtained from the basal regions of the plant, roots and root rhizosphere. Efforts are being made to identify these isolates to species level and to test for pathogenicity in pot trials.</div>