Poster Presentation Science Protecting Plant Health 2017

Identifying the mechanism of infection and colonisation by Verticillium dahliae in potato (#334)

Mee-Yung Shin 1 , Tonya J Wiechel 2 , Paul WJ Taylor 1
  1. Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville, Victoria, Australia
  2. Agriculture Australia, AgriBio Centre for AgriBioscience, Bundoora, Victoria, Australia

Verticillium wilt is an important disease of potato which is primarily caused by the soilborne fungus Verticillium dahliae, a pathogen that is widespread across commercial potato fields in south-eastern Australia. Previous studies have shown that cultivar Denali has moderate to high resistance to V. dahliae, while Russet Burbank is susceptible. However, the mechanism of infection and colonisation within the plant tissues of each cultivar, and the cause of host resistance within Denali is still unknown. Glasshouse pathogenicity tests were conducted by immersing the roots of each plant in a spore suspension (5x104 mL-1) for 5 mins prior to planting in soil in pots. The experimental control treatment consisted of dipping the plant roots in sterile distilled water. Each treatment had five replicates. Disease symptom severity was assessed weekly using a 0-5 qualitative scale, where 0 = healthy, 1 = chlorosis of leaves, 2 = moderate (30-50%) wilt with chlorosis, 3 = moderate wilt and necrosis, 4 = severe (>50%) wilt and necrosis, and 5 = plant death. Plants were destructively sampled at 2, 5 and 9 weeks after inoculation, and different host tissues were cultured on to ethanol potassium amoxycillin agar to determine the incidence of V. dahliae. A Taqman probe-based assay for real-time PCR was used to quantify the concentration of V. dahliae DNA in Denali and Russet Burbank stems at harvest. Overall, Denali consistently exhibited lower visual symptom severity than Russet Burbank. However, there appeared to be little difference in the incidence of infection of different host tissues and concentration of V. dahliae DNA in the stems of both cultivars.