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Title: The mating type idiomorphs of Fusicladium effusum: identification, frequency and spatial distribution in the southeastern USA

Author
item YOUNG, CAROLYN - Samuel Roberts Noble Foundation, Inc
item CHARLTON, NIKKI - Samuel Roberts Noble Foundation, Inc
item MATTUPALLI, CHAKRADHAR - Samuel Roberts Noble Foundation, Inc
item Wood, Bruce
item Bock, Clive

Submitted to: European Conference on Fungal Genetics Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 1/10/2016
Publication Date: 4/3/2016
Citation: Young, C.A., Charlton, N.D., Mattupalli, C., Wood, B.W., Bock, C.H. 2016. The mating type idiomorphs of Fusicladium effusum: identification, frequency and spatial distribution in the southeastern USA. European Conference on Fungal Genetics Proceedings. p. 265.

Interpretive Summary:

Technical Abstract: Fusicladium effusum is the causal agent of pecan scab, the most prevalent disease of pecan (Carya illinoinensis) in the southeastern USA. Infection by the pathogen can result in serious and even catastrophic yield loss when conditions are favorable for an epidemic. Despite earlier efforts to determine a sexual stage, F. effusum is currently known only by its asexual (conidial) stage. The degree and distribution of genetic diversity observed within and among populations of F. effusum are typical of a sexually reproducing fungal pathogen, and comparable to other dothideomycetes with a known sexual stage, including the closely related apple scab pathogen, Venturia inaequalis. The mating type mtAA (mat1-1) idiomorph was identified in a draft genome of F. effusum flanked by two conserved genes encoding a DNA lyase (apnB) and an uncharacterised PH domain-containing protein. The mating type locus, spanning the flanking genes, was amplified and sequenced in 14 isolates, collected from different geographic locations and cultivars, revealing that only 50% of the samples contained the mtAA idiomorph and are considered mating type A (MTA). The remaining samples contained the mtBA (mat1-2) idiomorph and are considered mating type B (MTB). A multiplex PCR screen was developed to amplify a conserved housekeeping gene (tubB), mtAA and mtBA, and used to screen 1203 F. effusum isolates collected from 13 pecan populations across the southeastern USA. A hierarchical sampling protocol representing region, orchard, tree and leaflet was followed at all sites so the mating type structure at different spatial scales could be assessed. Analysis of this collection revealed the frequency of the mating type idiomorphs is in a 1:1 equilibrium. The apparent equilibrium of the mating type idiomorphs provides impetus to a renewed effort to search for a sexual stage of F. effusum. Identification of a sexual stage will provide a fuller understanding of the disease epidemiology and pathogen population genetics, and eventually a basis for better management of existing resistance genes in pecan.