Abstract

While random amplification of polymorphic DNA (RAPD) markers linked to disease resistance genes have been widely used in plant breeding programs, they generally lack reproducibility. To overcome this major disadvantage and other drawbacks, RAPD markers can be converted into sequence characterized amplified region (SCAR) markers, which are genetically defined loci amplified by polymerase chain reaction (PCR) using specific primers. Thus, SCAR markers are typically more reproducible than RAPD markers, due to specific amplification of genomic regions. In this study, a previously identified RAPD marker AT9/917 that is linked to the Puccinia psidii Winter (rust) resistance gene 1 (Ppr1) in Eucalyptus grandis was successfully converted into a specific SCAR marker. Seven specific SCAR primers were designed based on cloning and sequencing of the RAPD marker AT9/917. Different pairs of SCAR primers were tested in an E. grandis family from a crossing between a resistant and a susceptible E. grandis. Prime pair SCAR AT99151L and AT9915914R produced amplicons of expected size. Restriction enzyme digestion of the amplicon revealed polymorphisms between the resistant and susceptible parents. Association analysis between phenotype (rust resistance) and SCAR genotypes in the E. grandis family suggests that this specific SCAR is useful for marker-assisted selection of E. grandis trees resistance to P. psidii Winter.

Key words: Plant breeding, molecular markers, random amplified polymorphic DNA (RAPD), Mark-assisted selection, sequence characterized amplified region (SCAR).