| 摘要 |
Disclosed are isolated nucleic acid molecules which comprise an Mla nucleotide sequence derived from an Mla locus (e.g. Mla1, 6, 12) encoding an MLA polypeptide which is capable of recognising and activating a race specific defence response in a plant into which the nucleic acid is introduced and expressed, in response to challenge with a cognate Erysiphe graminis isolate. Also disclosed are novel methods for selecting such sequences based on the determination of an Mla (AT)n micro-satellite identified by the present inventors. Also provided is an novel 3 component activity assay, for assessing the ability of nucleic acid encoding a putative resistance (R) gene to confer resistance against a pathogen expressing a cognate Avr gene, which comprises the steps of: (a) selecting plant material which comprises plant cells which express a recessive gene conferring resistance against the pathogen, (b) introducing into the plant material, nucleic acid encoding (i) a detectable marker, (ii) a dominant susceptibility gene which inhibits the resistance conferred by the recessive gene, and (iii) the putative R gene, (c) challenging the plant material with the pathogen, (d) observing cells in the plant material in which the marker is expressed to determine the amount of pathogen growth present, and (e) correlating the amount of pathogen growth with the ability of the R gene to confer resistance against the pathogen. Also provided are corresponding methods and materials (e.g. vectors, polypeptides, plants, kits) based on the use of Mla nucleotide sequences or identification methods.
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