Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract only
Publication Acceptance Date: 5/1/2005
Publication Date: 7/30/2005
Citation: Brooks, S.A., Huang, L., Herbel, M.N., Gill, B.S., Brown Guedira, G.L., Fellers, J.P. 2006. Structural variation and evolution of a resistance gene island in natural populations of wild wheat Aegilops tauschii [abstract]. Phytopathology. 95:S14. Interpretive Summary: Sequencing the genome allows a scientist to know the exact details of the genes that are in the particular organism of interest. It opens up windows into how one species is related to another and how the species have evolved. Though the whole wheat genome has not been sequenced, target areas of interest have been. This report tells of a region on chromosome 1 of the wheat relative, Aegilops tauscii, commonly known as goatgrass, that has been sequenced. We used this sequence to evaluate several Aegilops species that were collected around the fertile crescent. The data shows many of the collections have similar DNA patterns, while others do not. There seems to be correlations between what DNA sequence is present and where these wheat accessions were collected. Our evidence supports the idea that this region is a center of diversity for wheat and its relatives.
Technical Abstract: Genetic mapping and sequencing of plant genomes have been useful for investigating eukaryotic chromosome structural organization. In many cases analyses have been limited in the number of representatives sampled from specific groups. The degree of intraspecific genome diversity remains in question, and it is possible that a single model genome may have limited utility for identifying genes in related members of the species or genus. Genes of particular interest for crop-plant improvement are disease resistance genes that are harbored by wild relatives of modern cultivated crops. These genes are evolutionarily dynamic and under selective pressure by a broad range of pathogenic organisms. Representative genomic data is critical for efficient gene transfer-to agronomically superior albeit disease susceptible plant varieties. Using resistance gene analogs as models for resistance gene evolution, intraspecific genome comparisons were made among populations of wild diploid wheat (Aegilops tauschii). We observed deletion haplotypes occurring frequently and independently in the genome, where partial and total loss of gene complements is a common yet overlooked form of allelic variation. Haplotypes are geographically correlated and maintenance of gene complements in localized populations indicates selective advantage. Furthermore, deletion haplotypes are not detrimental to plant health, since genes without adaptive value in alternate environments are eliminated from the genome. This appears to be a common form of allelic variation in plants, and we address the consequences on genome restructuring and gene evolution.