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Title: DEVELOPMENT OF A SEQUENCE-TAGGED SITE(STS) MARKER FOR UR-11, A GENE CONFERRING RESISTANCE TO THE BEAN RUST FUNGUS, UROMYCES APPENDICULATUS

Author
item BOONE, W - CORNELL U., GENEVA EXP ST
item Stavely, J
item WEEDEN, N - CORNELL U., GENEVA EXP ST

Submitted to: Bean Improvement Cooperative Annual Report
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Due to the losses in production, losses to farmers, market instability, and consumer price increases resulting from epidemics of bean rust in edible common beans, resistance to rust is being incorporated into new bean cultivars by breeders. This rust resistance is controlled by single dominant genes, but the high degree of pathogenic variability in the fungus scausing bean rust indicates that incorporation of several such resistance genes should be accomplished to better insure that the resistance will not succumb to new pathogenic races. Although all of the identified rust resistance genes are dominant over susceptibility, certain of these genes are also dominant (epistatic) over others of these genes so it can be difficult and time consuming to determine if the second gene is present. Some of these genes have been tagged with DNA markers that provide an efficient means for detecting their presence. The most broadly effective rust resistance gene, Ur-11 is effective against 89 of the 90 available races of the rust fungus, but has had no such marker identified. This project was initiated to identify a DNA marker for the Ur-11 gene. A random primer, GTO2450, was identified that provides reliable identification of presence or absence of the Ur-11 gene in great northern, but not pinto or red, dry beans. Identification of this primer will facilitate combination of Ur-11 with other resistance genes in great northerns to facilitate development of resistant cultivars by breeders to reduce losses for farmers.

Technical Abstract: DNA was extracted from individual plants of inbred great northern dry bean lines and pooled separately from lines resistant or susceptible to the bean rust fungal pathogen, Uromyces appendiculatus. These lines and the resistance, conditioned by the Ur-11 major rust resistance gene, came from crossing a susceptible plant with a Ur-11 homozygous line, BelMiNeb 1. The eDNA pools were screened with 104 RAPD primers resulting in identification of two such RAPD primers that gave markers present only in the resistant pool. Each of these markers were isolated, cloned, and sequenced to design 16- to 19-mer oligonucleotides for specific amplification of the appropriate sequences. Only the GT02450 RAPD primer's 18- and 19-mer derivatives successfully distinguished plants with or without Ur-11 at a 65 degree C annealing temperature. From the F4 from crosses of susceptible great northerns with two BelMiNeb lines homozygous for Ur-11, plants with and without Ur-11 were identified at Beltsville, and leaf samples were sen to Geneva where the GT02450 marker was tested and shown to be tightly linked to Ur-11. However, this primer did not identify Ur-11 in pinto and small red dry beans.