A SCAR marker specific for rapid detection of the avirulence gene Avr1c in Phytophthora sojae

The F 2 population derived from a cross between isolates pR x ( Avr1c - Avr1c ) and ps 1 ( avr1c - avr1c ) of Phytophthora sojae , fungal agent of soybean stem and root rot, was used to determine the genetic basis of avirulence towards Rps 1c gene in soybean. The results indicated that this avirulence is dominant and controlled by a single locus, as expected for a simple gene-for-gene model. Segregation of Avr1c in the F 2 progeny of this cross fits a 3:1 ratio. Four of 80 AFLP primers effectively distinguished the avirulent pR x from the virulent ps 1 . Among the 5 specific markers, band C was amplified from the avirulent pR x by primer set EGC/MAT, then recovered and cloned. This AFLP marker was successfully transfered to a SCAR marker through sequencing, primer design and specific amplication of the DNA of the avirulent pR x . Results of validity and specificity experiments with 50 individuals of the F 2 progeny and 50 field isolates demonstrated that this SCAR marker (a 616-bp fragment) can be successfully and specifically amplified from the P. sojae isolates that have Avr1c gene.