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Consistent Quantitative Trait Loci in Pea for Partial Resistance to Aphanomyces euteiches Isolates from the United States and France

First and fifth authors: UMR INRA-AgroCampus Rennes, Amélioration des Plantes et Biotechnologies végétales, BP 35327, 35653 Le Rheu Cedex, France; second author: USDA-ARS Grain Legume Genetics and Physiology Research Unit, Washington State University, 303W Johnson Hall, Pullman, WA 99164; third author: Seneca Foods Corporation, Agricultural Research Department, 711 East Main Street, Dayton, WA 99328; fourth author: U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS), 24106 N. Bunn Rd., Prosser, WA 99350 (retired); and sixth author: USDA-ARS Western Regional Plant Introduction Station, Washington State University, 59 Johnson Hall, Pullman, WA 99164

Development of pea cultivars resistant to Aphanomyces root rot, the most destructive root disease of pea worldwide, is a major disease management objective. In a previous study of a mapping population of 127 recombinant inbred lines (RILs) derived from the cross ‘Puget’ (susceptible) × ‘90-2079’ (partially resistant), we identified seven genomic regions, including a major quantitative trait locus (QTL), Aph1, associated with partial resistance to Aphanomyces root rot in U.S. fields (21). The objective of the present study was to evaluate, in the same mapping population, the specificity versus consistency of Aphanomyces resistance QTL under two screening conditions (greenhouse and field, by comparison with the previous study) and with two isolates of Aphanomyces euteiches originating from the United States and France. The 127 RILs were evaluated in the greenhouse for resistance to pure culture isolates SP7 (United States) and Ae106 (France). Using the genetic map previously described, a total of 10 QTL were identified for resistance in greenhouse conditions to the two isolates. Among these were Aph1, Aph2, and Aph3, previously detected for partial field resistance in the United States. Aph1 and Aph3 were detected with both isolates and Aph2 with only the French isolate. Seven additional QTL were specifically detected with one of the two isolates and were not identified for partial field resistance in the United States. The consistency of the detected resistance QTL over two screening environments and isolates is discussed with regard to pathogen variability, and disease assessment and QTL detection methods. This study suggests the usefulness of three consistent QTL, Aph1, Aph2, and Aph3, for marker-assisted selection.

Additional keywords: Pisum sativum .