Optimal population size for RFLP-assisted cultivar identification in alfalfa (Medicago sativa L.)

The ability of RFLP markers to distinguish between 2 heterogeneous alfalfa ecotypes, "Vogherese" and "Maremmana", was correlated with the number of pl ants sampled in either single-plant or bulk analyses. Independent subsample populations of 20 and 50 plants were compared for variance component parti tioning and band frequencies in 20-, 50- and 100-plant subpopulations of Ma remmana. Homogeneity within 3 independent bulks of the same size as given a bove was taken as a measure of bulk optimal size. A minimum of 50 plants is required for both single-plant and bulk analyses; however, for a large maj ority of bands analysed, no significant differences were detected for their frequency among populations of 20, 50 and 100 plants, with the exception o f 6 bands out of 48. One ecotype-specific marker was found through bulk ana lysis. Results are discussed in relation to the improvement of RFLP methodo logy for cultivar identification in alfalfa.