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Molecular genetic description of the cryptic wheat-Aegilops geniculata introgression carrying rust resistance genes Lr57 and Yr40 using wheat ESTs and synteny with rice

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Abstract:

The cryptic wheat-alien translocation T5DL·5DS-5MgS(0.95), with leaf rust and stripe rust resistance genes Lr57 and Yr40 transferred from Aegilops geniculata (UgMg) into common wheat, was further analyzed. Molecular genetic analysis using physically mapped ESTs showed that the alien segment in T5DL·5DS-5MgS(0.95) represented only a fraction of the wheat deletion bin 5DS2-0.78-1.00 and was less than 3.3 cM in length in the diploid wheat genetic map. Comparative genomic analysis indicated a high level of colinearity between the distal region of the long arm of chromosome 12 of rice and the genomic region spanning the Lr57 and Yr40 genes in wheat. The alien segment with genes Lr57 and Yr40 corresponds to fewer than four overlapping BAC or PAC clones of the syntenic rice chromosome arm 12L. The wheat-alien translocation breakpoint in T5DL·5DS-5MgS(0.95) was further localized to a single BAC clone of the syntenic rice genomic sequence. The small size of the terminal wheat-alien translocation, as established precisely with respect to Chinese Spring deletion bins and the syntenic rice genomic sequence, further confirmed the escaping nature of cryptic wheat-alien translocations in introgressive breeding. The molecular genetic resources and information developed in the present study will facilitate further fine-scale physical mapping and map-based cloning of the Lr57 and Yr40 genes.

La translocation cryptique T5DL·5DS-5MgS(0.95), laquelle confère la résistance à la rouille brune et à la rouille striée suite au transfert des gènes Lr57 et Yr40 de l’Aegilops geniculata (UgMg) au blé tendre, a été étudiée. Des analyses moléculaires au moyen d’EST de position connue sur la carte physique ont montré que le segment d’ADN étranger présent au sein de T5DL·5DS-5MgS(0.95) ne représente qu’une fraction de la délétion 5DS2-0.78-1.00 chez le blé et mesurait moins de 3,3 cM sur la carte génétique du blé diploïde. Des analyses génomiques comparées ont indiqué une importante colinéarité entre la région distale du bras long du chromosomes 12 du riz et la région incluant les gènes Lr57 et Yr40 chez le blé. Le segment étranger portant les gènes Lr57 et Yr40 correspond à une région qui couvre moins de quatre clones BAC/PAC chevauchants chez le bras chromosomique 12L, lequel est synténique chez le riz. Le point de translocation au sein de T5DL·5DS-5MgS(0.95) a été situé dans un seul clone BAC portant la région correspondante chez le riz. La petite taille de la translocation terminale, telle que révélée précisément par l’analyse des délétions chez Chinese Spring et de la région correspondante chez le riz, a de nouveau confirmé la nature élusive des translocations impliquant de la chromatine étrangère suite à des introgressions chez le blé. Les ressources moléculaires et l’information obtenue dans ce travail vont faciliter une cartographie physique plus fine et le clonage positionnel des gènes Lr57 et Yr40.

Document Type: Research Article

Publication date: 2009-12-01

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  • From its inception in 1957, this international cytogenetics journal has catered to the research areas of the members of the Genetics Society of Canada; traditionally, these have included agriculture, entomology, genetics/cytogenetics, and evolutionary mechanisms. The contents of the journal have evolved as contributors developed new technologies and interests. A 20-member Editorial Board is composed of scientists from around the world. Reviews and commentary from respected experts are often featured.
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