Genetic Characterization and Cloning of the Barley Ml-a Locus

大麦白粉病是由专性真菌病原菌Erysiphe graminis f. sp. hordei引起的，为研究介导抗性的寄主基因提供了若干有利条件。这种疾病已经被深入研究了50多年；因此，有广泛的生理数据和遗传材料基础，这是大多数其他宿主/病原体系统无法比拟的。大麦Ml-a基因座特别令人感兴趣，因为在这个基因座上已经鉴定出了30多个抗性等位基因。通过筛选118,000 M2幼苗，我分离出41个部分或完全易感突变体。这些新等位基因的互补分析将用于确定Ml-a基因座的遗传结构，它可能代表一个复杂的基因座或紧密连接的基因簇。此外，突变体将利用减法杂交实验分离Ml-a cDNA克隆。目前还没有从任何植物中克隆出这种抗病基因。对Ml-a克隆的分析将提供有关Ml-a位点等位基因变异的性质和Ml-a基因产物在介导抗病性中的生化作用的信息。＊＊＊

9402315 Somerville The powdery mildew disease of barley, caused by the obligate fungal pathogen Erysiphe graminis f. sp. hordei, offers several advantages for the study of host genes mediating resistance. This disease has been studied intensively for more that 50 years; thus, there is an extensive base of physiological data and genetic materials available that is unmatched by most other host/pathogen systems. The barley Ml-a locus is of particular interest in that more that 30 resistance alleles have been identified at this locus. By screening 118,000 M2 seedlings, I have isolated 41 partially or fully susceptible mutants. Complementation analysis of these new alleles will be used to determine the genetic structure of the Ml-a locus, which may represent either a complex locus or cluster of tightly linked genes. Also, the mutants will be exploited in subtractive hybridization experiments to isolated Ml-a cDNA clones. No such disease resistance gene has been cloned form any plant. %%% Analysis of the Ml-a clones will provide information about the nature of the allelic variation at the Ml-a locus and about the biochemical role of the Ml-a gene product in mediating disease resistance. ***