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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #346978
Title: Evidence for sexual reproduction in Venturia effusa, causal agent of pecan scab

Author
item YOUNG, CAROLYN - Samuel Roberts Noble Foundation, Inc
item Bock, Clive
item CHARLTON, NIKKI - Samuel Roberts Noble Foundation, Inc
item CHARKRADHAR, MATTUPALLI - Samuel Roberts Noble Foundation, Inc
item YI, MIHWA - Samuel Roberts Noble Foundation, Inc
item PLUMMER, KIM - University Of Auckland
item BOWEN, JOANNA - New Zealand Institute Of Plant & Food Research
item TEMPLETON, MATTHEW - New Zealand Institute Of Plant & Food Research
item WOOD, BRUCE - Retired ARS Employee

Submitted to: Mycological Society of America
Publication Type: Abstract Only
Publication Acceptance Date: 6/2/2017
Publication Date: 7/19/2017
Citation: Young, C.A., Bock, C.H., Charlton, N.D., Charkradhar, M., Yi, M., Plummer, K.M., Bowen, J.K., Templeton, M., Wood, B.W. 2017. Evidence for sexual reproduction in Venturia effusa, causal agent of pecan scab [abstract]. Mycological Society of America. p. 87.

Interpretive Summary:

Technical Abstract: Pecan scab caused by Venturia effusa is widespread across southwest USA and epidemics can result in catastrophic yield loss. Venturia effusa reproduces asexually during the active phase of the disease cycle (spring through summer) with no evidence of a sexual cycle. Yet, genetic diversity among populations of pecan scab suggest V. effusa is a sexually reproducing pathogen. Using BLASTX with the mating type loci of V. inaequalis (apple scab pathogen) we were able to identify the mat1-1-1 idiomorph in V. effusa isolate 3Des10b genome flanked by two conserved genes encoding a DNA lyase (apnB) and an uncharacterised PH domain-containing protein. Evaluation of 14 isolates collected from different geographic locations and cultivars by PCR showed that 50% contained mat1-1-1 and the remaining isolates contained mat1-2-1. A multiplex PCR assay developed to amplify tubB, mat1-1-1 and mat1-2-1, was used to screen 1203 V. effusa isolates collected from 13 pecan populations across the southeastern USA. The sampling protocol represented region, orchard, tree and leaflet 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 of MAT1-1:MAT1-2. In vitro paired matings resulted in the formation of pseudothecia only between isolates of the opposite mating types indicating that V. effusa is heterothallic. Identification of the sexual stage in nature will provide improved understanding of the disease epidemiology, pathogen population genetics, and potentially provide insight into novel approaches to manage this disease.