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Theor Appl Genet (2011) 123:207218 DOI 10.1007/s00122-011-1577-9
ORIGINAL PAPER
Collinearity-based marker mining for the ne mapping of Pm6, a powdery mildew resistance gene in wheat
Bi Qin Aizhong Cao Haiyan Wang Tingting Chen
Frank M. You Yangyang Liu Jianhui Ji Dajun Liu
Peidu Chen Xiu-e Wang
Received: 13 December 2010 / Accepted: 15 March 2011 / Published online: 6 April 2011 Springer-Verlag 2011
Abstract The genome sequences of rice (Oryza sativaL.) and Brachypodium distachyon and the comprehensive Triticeae EST (Expressed Sequence Tag) resources provide invaluable information for comparative genomics analysis. The powdery mildew resistance gene, Pm6, which was introgressed into common wheat from Triticum timopheevii, was previously mapped to the wheat chromosome bin of 2BL [fraction length (FL) 0.501.00] with limited DNA markers. In this study, we saturated the Pm6 locus in wheat using the collinearity-based markers by extensively exploiting these genomic resources. All wheat ESTs located in the bin 2BL FL 0.501.00 and their corresponding orthologous genes on rice chromosome 4 were rstly used to develop STS (Sequence Tagged Site) markers. Those identied markers that anked the Pm6 locus were then used to identify the collinear regions in the genomes of rice and Brachypodium. Triticeae ESTs with orthologous genes in these collinear regions were further used to develop new conserved markers for the ne mapping of Pm6. Using two F2 populations derived from crosses of IGVI-465 9 Prins
and IGVI-466 9 Prins, we mapped a total of 29 markers to the Pm6 locus. Among them, 14 markers were co-segregated with Pm6 in the IGVI-466/Prins population. Comparative genome analysis showed that the collinear region of the 29 linked markers covers a *5.6-Mb region in chromosome 5L of Brachypodium and a *6.0-Mb region in chromosome 4L of rice. The marker order is conserved between rice and Brachypodium, but re-arrangements are present in wheat. Comparative mapping in the two populations showed that two conserved markers (CINAU123 and CINAU127) anked the Pm6 locus, and an LRR-receptor-like protein kinase cluster was identied in the collinear regions of Brachypodium and rice. This putative resistance gene cluster provides a potential target site for further ne mapping and cloning of Pm6. Moreover, the newly developed conserved markers closely linked to Pm6 can be used for the marker-assisted selection (MAS) of Pm6...