Marker Assisted Selection for Rhizomania Resistance in Sugar Beet Genotypes

Rhizomania disease is the most important disease of sugar beet in Iran and some other parts of the world, and plays a significant role in decreasing sugar yield. The best approach to combat the disease is to use resistant cultivars. In order to use the disease resistance genes in breeding programs, it is necessary to tag these genes with molecular markers. In order to identify the rhizomania-resistant plants within 103 sugar beet genotypes including S1, S2 and F2 populations, a coupling-phase SCAR marker (named PN1) and a repulsion-phase RAPD marker (named PN3) linked to rhizomania resistance gene were used. Genomic DNA was extracted from the leaf samples taken from the single plants. In the next step, primers related to PN1 and PN3 markers were individually tested on some single plant DNAs by RAPD-PCR and Specific PCR methods. Amplified products were separated by gel electrophoresis, stained with ethidium bromide, observed using gel documentation device and scored according to the presence and absence of marker band. According to the marker data, percent dominant homozygous plants were found to be between 0 to 92%. The O-types numbers 1025, 1036, 1011, 201-20 and 201-25 were found to be the most disease resistant genotypes. Therefore, it seems PN3 marker, after converting to SCAR specific marker, along with PN1 marker can be utilized in one duplex PCR reaction to identify each of the three genotypes (Rz1Rz1, Rz1rz1 and rz1rz1) and screen rhizomania resistant breeding lines and populations originated from Rz1 source.