Submitted to: Proceedings International Barley Genetics Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 10/15/2000
Publication Date: N/A
Technical Abstract: Obligate fungal pathogens, such as 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 (=Erysiphe) graminis. It is most damaging to barley in cool, wet climates, and can reduce yields up to 25%. The primary means of disease control is by incorporation of genetic resistance into elite varieties. To discern the fundamental signaling mechanisms between the host plant cell and fungal pathogen, we have chosen the Mla resistance-gene cluster in barley as our model system. Approximately 30 variants of the Mla locus have been identified in different cultivars, each giving a race- specific response to different isolates of B. graminis f. sp. hordei (reviewed by J rgensen 1994). This extensive variability provides an ideal research tool to explore resistance-signaling mechanisms elicited by cereal lhosts to obligate fungal biotrophs, as well as the evolution of new resistance-gene specificities. In preparation for positional-cloning of the Mla locus, we saturated the Mla region with molecular markers and the Mla locus was delimited to a 240-kb physical interval bridged by two overlapping BAC (Bacterial Artificial Chromosome) clones. As a first step to unravel the evolutionary mechanisms that gave rise to this interesting gene-rich region, we determined the complete DNA sequence of these Mla- spanning clones. This is the first description of the complete DNA sequence of a complex resistance gene cluster from cereal crops. The results described in this manuscript will impact scientists that work in the area of resistance gene signaling and molecular pathology as well as the field of plant pathology and molecular breeding.