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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #328621
Title: Evidence for sexual reproduction in Fusicladium effusum

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

Submitted to: National American Phytopathology Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 5/16/2016
Publication Date: 12/1/2016
Citation: Charlton, N.D., Mattupalli, C., Wood, B.W., Bock, C.H., Young, C.A. 2016. Evidence for sexual reproduction in Fusicladium effusum [abstract]. National American Phytopathology Meetings. 106-S:S4.9.

Interpretive Summary: Fusicladium effusum is the causal agent of pecan scab, the most prevalent and often catastrophic disease of pecan in the southeastern USA. Despite earlier efforts to determine a sexual stage, reproduction in F. effusum has been observed only by asexually produced conidia. However, the degree and distribution of genetic diversity observed within and among populations of F. effusum are typical of a sexually reproducing fungus. The mating type locus was identified in a draft genome of F. effusum and was amplified and sequenced in 14 isolates collected from different geographic locations and cultivars, revealing that 50% of the samples contained the mtAA idiomorph and are considered mating type A (MTA). The remaining samples contained mtBA and are mating type B (MTB). A multiplex PCR screen was developed to amplify mtAA, mtBA and tubB, and used to screen 1203 isolates of F. effusum from 13 pecan populations across the southeastern USA. Analysis of this collection revealed the frequency of the mating type idiomorphs is in a 1:1 equilibrium. Select isolates were crossed in pairwise combinations on oatmeal agar and after six months, organs typical of immature sexual fruiting bodies were observed, indicating existence of a putative sexual stage. Identification of a sexual stage will provide improved understanding of the disease epidemiology and pathogen population genetics, and potentially provide insight into novel approaches to manage this damaging disease.

Technical Abstract: Fusicladium effusum is the causal agent of pecan scab, the most prevalent and often catastrophic disease of pecan in the southeastern USA. Despite earlier efforts to determine a sexual stage, reproduction in F. effusum has been observed only by asexually produced conidia. However, the degree and distribution of genetic diversity observed within and among populations of F. effusum are typical of a sexually reproducing fungus. The mating type locus was identified in a draft genome of F. effusum and was amplified and sequenced in 14 isolates collected from different geographic locations and cultivars, revealing that 50% of the samples contained the mtAA idiomorph and are considered mating type A (MTA). The remaining samples contained mtBA and are mating type B (MTB). A multiplex PCR screen was developed to amplify mtAA, mtBA and tubB, and used to screen 1203 isolates of F. effusum from 13 pecan populations across the southeastern USA. Analysis of this collection revealed the frequency of the mating type idiomorphs is in a 1:1 equilibrium. Select isolates were crossed in pairwise combinations on oatmeal agar and after six months, organs typical of immature sexual fruiting bodies were observed, indicating existence of a putative sexual stage. Identification of a sexual stage will provide improved understanding of the disease epidemiology and pathogen population genetics, and potentially provide insight into novel approaches to manage this damaging disease.