Oral Presentation Science Protecting Plant Health 2017

Molecular-based strategies for combating Fusarium wilt disease of legumes (3884)

Louise F Thatcher 1 , Angela H Williams 1 2 , Gagan Garg 1 , Karam B Singh 1 2
  1. Agriculture and Food, CSIRO, Floreat, WA, Australia
  2. The Institute of Agriculture, University of Western Australia, Crawley, WA, Australia

Fusarium wilt disease caused by pathogenic F. oxysporum isolates are major constraints to global legume production, accounting for losses up to 90%  annually, and are significant biosecurity threats to Australia’s major legume industries, particularly chickpea worth ~$1B (2016). Substantial crop losses, no curative treatments and persistence of pathogen spores in soil ranks F. oxysporum high on the list of globally important plant pathogens. Strict quarantine regulations prevent import of legume-infecting isolates into Australia for research purposes. To reduce the probable impact of this pathogen on Australian legume industries we developed a model pathosystem using the model legume Medicago truncatula and a F. oxysporum f. sp. medicaginis isolate (Fom) with the aim of providing resources and expertise to combat disease incursion. To dissect pathogenicity mechanisms we generated a high quality Fom genome assembly including almost near complete assembly of its predicted pathogenicity chromosome. This latter scaffold sequence contains all Fom homologs of the tomato F. oxysporum f. sp. lycopersici Secreted In Xylem (SIX) pathogenicity-associated genes. Using genomic location and relative increase in in planta expression as an indicator of key roles in pathogen attack, high-depth RNA-sequencing of the Fom transcriptome at various stages of host infection and in vitro confirmed expression of candidate SIX effectors and facilitated prediction of novel candidate effectors. Further novel machine-learning based effector prediction algorithms developed in CSIRO were applied to determine a Fom pathogenicity effector set which assessed against the genomes of other Fusaria and those pathogenic on legumes (e.g. F. oxysporum f. sp. ciceris; chickpea infecting), identified 5 candidate effectors highly conserved amongst legume-infecting isolates. These effectors may be useful tools for pre-emptive breeding of Australian chickpea cultivars to protect against bioinvasion of globally destructive F. oxysporum f. sp. ciceris isolates.

  1. Williams AH, Thatcher LF, Sharma M, Azam S, Hane JK, Kidd BN, Anderson JA, Ghosh R, Garg G, Lichtenzveig J, Kistler HC, Shea T, Young S, Buck SA, Kamphuis LG, Saxena R, Pande S, Ma LJ, Varshney RK, Singh KB (2016) Comparative Genomics of Legume-infecting Fusarium oxysporum formae speciales Informs Prediction of Lineage-specific Sequences Related to Pathogenicity. BMC Genomics. 17: 191 DOI: 10.1186/s12864-016-2486-8
  2. Thatcher LF, Williams H Garg G, Sally-Anne Buck G, Karam B. Singh B. (2016) Transcriptome analysis of the fungal pathogen Fusarium oxysporum f. sp. medicaginis during colonisation of resistant and susceptible Medicago truncatula hosts identifies differential pathogenicity profiles and novel candidate effectors. BMC Genomics DOI 10.1186/s12864-016-3192-2