Poster Presentation Science Protecting Plant Health 2017

Is there a correlation between virulence and VCG type in Australian Verticillium dahliae isolates? (#115)

Pearl Dadd-Daigle 1 2 , Maurizio Labbate 2 , Piklu Roy Chowdhury 2 , Karen Kirkby 1 , Toni Chapman 1
  1. Department of Primary Industries, NSW
  2. University of Technology Sydney, Sydney

Verticillium dahliae is a soil-borne ascomycete that infects hundreds of agriculturally important crops globally, including cotton. In Australia, cotton is a continuously growing billion-dollar industry. Cotton yields have increased from 500 kg per hectare in the 1960’s, to 2000 kg per hectare in 2013. Sustainability and growth of the cotton industry is reliant on improved cotton varieties, soil and water management, and weed, insect and disease management.

Verticillium dahliae, the pathogen that causes Verticillium wilt in cotton, has been described according to vegetative compatibility groups (VCGs). Disease symptoms in different plant hosts are generally associated with different VCGs, and internationally, cotton is reported to be most impacted by the defoliating VCG1A. This strain causes severe disease including defoliation of cotton plants, while VCGs 2A and 4B are non-defoliating and cause less severe disease symptoms. Until recently, VCG1A was not reported to be present in Australia, and in the 2015/2016 season was not showing the expression of symptoms observed internationally. In Australia, on a disease severity scale there have been reports of VCG2A’s are causing more damage than the defoliating VCG1A.

This Australian disease conundrum raises the question of the association between VCG and pathogenicity. This is being addressed through molecular and pathogenicity assays on isolates collected from infected plants in commercial cotton fields over the past 30 years of NSW disease surveys. Through improved understanding of this pathogen and its presence in Australia we can work towards improved diagnostic detection and crop management.