Assessment of RAPD marker frequencies over cycles of recurrent selection for pigment concentration and percent solids in red beet (Beta vulgaris L)

In the past twenty years, betalain pigments found in red beet (Beta vulgaris L.) have been adopted for use as natural red food colorings. Utility and er;tractability of these compounds is dependent upon native concentrations of both pigment and total dissolved solids. In an effort to develop red beet populations with elevated levels of betalain pigment, recurrent half-sib family selection for high pigment and both high and low solids was practiced for seven cycles. This scheme resulted in the development of a high pigment/high solids and a high pigment/low solids population. A total of 200 randomly chosen oligonucleotide decamer primers were used to amplify genomic DNA of individual plants in the selection scheme for repeatability and clarity of amplification products. Thirty-one primers were chosen on this basis and used to assess random-amplified polymorphic DNA (RAPD) marker frequencies on genomic DNA samples isolated from 47 randomly-chosen individual plants in each of cycles 1, 3, and 6 in both high pigment/high solids and high pigment/low solids. Number of scorable Polymerase Chain Reaction products ranged from 1-10, resulting in a total of 161 RAPD markers. Chi-square and regression analyses were performed to determine the presence/absence of a linear trend in marker frequencies during the selection scheme. Comparisons were made among cycles within high pigment/high solids and high pigment/low solids populations. Significant linear trends were detected in both cases for certain RAPD markers. Formulae were used to test whether observed linear marker frequency trends were due to the effects of selection or random genetic drift. Chi-square tests revealed a subset of markers which exhibited significant frequency changes across cycles changed due to selection. These data demonstrate changes in RAPD marker frequencies with recurrent selection and suggest linkage of RAPD markers to genes controlling pigment in red beet.