Repeatability of Some Molecular Markers Linked to Rhizomania Resistance Gene (Rz1) in Sugar Beet (Beta vulgaris L.) Genotypes

Rhizomania disease is one of the most important diseases of sugar beet in Iran and many other parts of the world, and plays an essential role in decreasing sugar yield in fields. The best approach to control this disease is to use resistant varieties. For the involvement of resitance genes in breeding programs, tagging these genes by molecular markers is necessary. In this approach, some breeding populations and commercial varieties of sugar beet originated from Rz1 resistance source were used for validation and repeatability of some coupling molecular markers obtained from past studies. Accordingly, ELISA data related to greenhouse evaluation of rhizomania resistance were used in some breeding populations. For molecular analysis, leaf samples were taken from the plants and after DNA extraction, RAPD or PCR using related primers to markers were performed. Amplified products were separated by gel electrophoresis, stained with ethidium bromide, observed using gel documentation device and scored according to presence and absence of marker bands. Percentages of agreement between the markers results with ELISA data in single plants were estimated in breeding populations and the percent presence of the markers in commercial varieties were determined. Comparison between ELISA and molecular analysis results showed that among these markers, two coupling markers named PN1 and PN2 with ELISA agreement proportion of 57% and 71% respectively, an α error of 6% and presence of more than 80% in resistant varieties are the most suitable coupling markers to identify Rz1 resistance allel.