|Gobelman Werner, Karin|
Submitted to: Journal of Agricultural Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2000
Publication Date: N/A
Interpretive Summary: Obligate fungal pathogens (e.g., rusts and mildews) are perhaps the greatest deterrent to cereal production worldwide. Powdery mildew of grasses (barley, wheat, rye, and oats) is caused by the obligate fungal pathogen, Blumeria graminis. Powdery mildew is consistently an important disease of barley, resulting in reduced grain yield, kernel weight, and grain protein. The primary means of disease control is by incorporation o genetic resistance into elite varieties. Genes that confer resistance to disease are usually identified only by their phenotype. Thus, in large-genome cereal crops such as barley, a map-based approach is one of the only alternatives for identifying genes that confer disease resistance. In this report, we describe the identification and characterization of RAPD (Random Amplified Polymorphic DNA)-derived markers flanking the Mla cluster for use in map-based gene isolation. These molecular markers were critical lfor the isolation of the Mla resistance gene, the first gene cloned that confers active disease defense in small grain cereal crops. The results described in this manuscript will impact scientists who work in the area of molecular plant pathology and molecular breeding.
Technical Abstract: Over 30 variants of the Mla (powdery mildew) resistance cluster on chromosome 5 (1H) have been identified in barley. In this report, we describe the use of RAPDs (Random Amplified Polymorphic DNAs) and bulked segregant analysis to identify DNA markers flanking the Mla cluster. Seven hundred and thirty-nine RAPD primers were used to compare pools of recombinant lines that contained the (Mla6 + Mla14) or the (Mla13 + Ml-Ru3 resistance specificities, respectively. A 1500-bp DNA fragment amplified by primer OPA-10 mapped between Hor1 and XChs3. Similarly, a 950-bp DNA fragment amplified by primer UBC-465 is located between XChs3 and Xmwg068. Finally, a 1626-bp DNA fragment amplified by primer UBC-165 mapped 0.28 cM proximal to the Mla cluster. Twenty sequenced-tagged site (STS) primers were developed from the UBC-16521626 sequence. Eight STS products amplified from UBC-16521626 primers mapped 0.28 cM distal to the Mla resistance cluster. One of these STS primer pairs, designated P0 and P1034RC, was used to identify tightly linked YAC clones from the cultivars Ingrid and Franka.