Marker-assisted selection for two rust resistance genes in sunflower

In this study we report on the identification of molecular markers, OX20 and OO04, linked to the gene R(Adv) in the proprietary inbred line P2. This gene confers resistance to most of the pathotypes of Puccinia helianthi identified in Australia Analysts indicates these RAPD markers are linked to the resistance locus at 0.0 cM and 11 cM respectively SCAR markers SCX20 and SCO04 derived from these two RAPD markers, and SCT06 derived from a previously reported RAPD marker linked at 4.5 cM from the R rust resistance gene were developed. SCX20 and SCO04 were linked at similar distances from their resistance locus as the RAPD markers. SCTO6 co-segregated completely with rust resistance. The robustness of the R SCAR marker was demonstrated through the amplification of the marker in a diverse range of sunflower germplasm considered to possess the R gene. The SCAR markers for R(Adv) were not amplified in the sunflower rust differential set thereby supporting the contention that this is a novel resistance gene. They did amplify in a number of proprietary lines closely related to the line P2. This locus is under further investigation as it will be useful in our attempts to use molecular-assisted breeding to produce durable resistance in sunflower to P. helianthi