title: Genetic and physical mapping of Avr1a in Phytophthora sojae.
abstract: The interaction between soybean and the phytopathogenic oomycete Phytophthora sojae is controlled by host resistance (Rps) genes and pathogen avirulence (Avr) genes. We have mapped the Avr1a locus in F(2) populations derived from four different P. sojae races. Four RAPD and nine AFLP markers linked to Avr1a were initially identified. Nine markers were used to compare genetic linkage maps of the Avr1a locus in two distinct F(2) populations. Distorted segregation ratios favoring homozygous genotypes were noted in both crosses. Segregation analysis of all the markers in one F(2) population of 90 progeny generated a map of 113.2 cM encompassing Avr1a, with one marker cosegregating with the gene. The cosegregating DNA marker was used to isolate P. sojae BAC clones and construct a physical map covering 170 kb, from which additional DNA markers were developed. Three markers occurring within the BAC contig were mapped in an enlarged population of 486 F(2) progeny. Avr1a was localized to a 114-kb interval, and an average physical to genetic distance ratio of 391 kb/cM was calculated for this region. This work provides a basis for the positional cloning of Avr1a.
authors.affiliation: Agriculture and Agri-Food Canada, London, Ontario N5V 4T3, Canada.
authors.forename: Terry
authors.initials: T
authors.lastname: MacGregor
authors.forename: Madan
authors.initials: M
authors.lastname: Bhattacharyya
authors.forename: Brett
authors.initials: B
authors.lastname: Tyler
authors.forename: Ravindra
authors.initials: R
authors.lastname: Bhat
authors.forename: August F
authors.initials: AF
authors.lastname: Schmitthenner
authors.forename: Mark
authors.initials: M
authors.lastname: Gijzen
mesh_terms: D020418:Algal Proteins / Q000235:genetics*; D002874:Chromosome Mapping; D022202:Chromosomes, Artificial, Bacterial; D003433:Crosses, Genetic; D005656:Fungal Proteins / Q000235:genetics; D005799:Genes, Dominant; D005800:Genes, Fungal; D005819:Genetic Markers; D010838:Phytophthora / Q000235:genetics* / Q000472:pathogenicity; D014774:Virulence
chemical_list: D020418:Algal Proteins; D005656:Fungal Proteins; D005819:Genetic Markers