|Coyne, Clarice - Clare|
Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2002
Publication Date: 1/1/2002
Citation: PILET-NAYEL, M., MUEHLBAUER, F.J., MCGEE, R., KRAFT, J., BARANGER, A., COYNE, C.J. QUANTITATIVE TRAIT LOCI FOR FIELD PARTIAL RESISTANCE TO APHANOMYCES ROOT ROT IN PEA. JOURNAL OF THEORETICAL AND APPLIED GENETICS. 2002. Interpretive Summary: Identification of quantitative resistance to Aphanomyces root rot in pea germplasm is critical for the continued economic production of pea in the United States. This paper reports work in which the first molecular markers identifying the specific genomic regions that explain the most important loci conferring genetic resistance to this destructive disease. Additionally, the most consistent criteria (above-ground rating at 50 percent flowering) for assessing genetic resistance in the field was identified. Also, a high-density map of pea was constructed that can be used to precisely locate other genes of economic interest and lays the foundation for map-based-cloning of resistance genes in pea. Flanking markers for a major Aphanomyces resistance QTL, Aph1, have been identified which could be useful in marker assisted selection to improve efficiency of breeding.
Technical Abstract: Aphanomyces root rot, caused by Aphanomyces euteiches Drechs, is the most important disease of pea (Pisum sativum L.) worldwide. No efficient chemicals are available to control the fungus. To facilitate breeding for Aphanomyces root rot resistance and to better understand the inheritance of partial resistance, our goal was identify QTL associated with field partial lresistance to A. euteiches. A population of 127 F10-derived RILs, from the cross Puget (susceptible) x 90-2079 (partially resistant), was used. The lines were assessed for resistance to A. euteiches under field conditions at two locations in the United States (Pullman, WA and LeSueur, MN) in 1996 and 1998, for three disease resistance criteria based on symptom intensity and disease effect on the whole plant. The RILs were genotyped using automated AFLP, RAPD, SSR, ISSR, STS, isozymes and morphological markers. The resulting genetic map consisted of 324 linked markers distributed over 13 linkage groups covering 1094 cM (Kosambi). Twenty seven markers were anchored to other published pea genetic maps. A total of 7 genomic regions were associated with Aphanomyces root rot resistance. The first one, located on LG IVb and named Aph1, was considered as major since it was highly consistent over the years, locations and resistance criteria studied and it explained up to 47 percent of the variation in the 1998 Minnesota trial. Two other year-specific QTL, namely Aph2 and Aph3, were consistently revealed from differen scoring criteria on LG V and Ia, respectively. Aph2 and Aph3 mapped near the r(wrinkled/round seeds) and af(normal/afila leaves) genes and accounted for up to 32 percent and 11 percent of the variation, respectively. Four other minor QTL, identified on LG Ib, VII and B, were specific to one environment and one resistance criterion.