Theor App! Genet (1997) 94:20-26 © Springer-Verlag 1997 T. Helms • J. Orf • G. Vallad • P. McClean Genetic variance, coefficient of parentage, and genetic distance of six soybean populations Received: 24 April 1996 / Accepted: 17 May 1996 Abstract Plant breeders would like to predict which biparental populations will have the largest genetic variance. If the population genetic variance could be predicted using coefficient of parentage or genetic dis- tance estimates based on molecular marker data, breeders could choose parents that produced segregat- ing populations with a large genetic variance. Three biparental soybean {Glycine max (L.) Merr.} popula- tions were developed by crossing parents that were closely related, based on pedigree relationships. Three additional biparental populations were developed by crossing parents that were assumed to be unrelated. The genetic variance of each population was estimated for yield, lodging, physiological maturity, and plant height. Coefficient of parentage was calculated for each pair of parents used to develop the segregating populations. Genetic distance was determined, based on the number of random amplified polymorphic markers (RAPD) that were polymorphic for each pair of parents. Genetic distance was not associated with the coefficient of par- entage or the magnitude of the genetic variance. The genetic variance pooled across the three closely related populations was smaller than the genetic variance pooled across the three populations derived from crossing unrelated parents for all four traits that were evaluated. Key words Glycine max • DNA • Pedigree analysis Genetic variance Communicated by E. J. Eisen T. Helms (^) • G. Vallad • P. McClean Department of Plant Sciences, North Dakota State University, Fargo, ND 58105, USA J. Orf Department of Agronomy and Plant Genetics, University of Min- nesota, St. Paul, MN 55108, USA Introduction Plant breeders that develop segregating popula from biparental crosses would like to predict the m and genetic variance of experimental lines derived f each two-parent combination. Populations with a mean and large genetic variance would be excepted the most useful for developing improved cultivars. Prediction of the population mean from the m parent mean has been evaluated by several inves tors. Busch et al. (1974) found that the mean yield o populations of experimental lines of wheat (Triticum aestivum L.) was highly correlated (r = 0.73, P = 0.01) with mid-parent means. Souza and Sorrells (1991) found means of three traits were not significantly different the mid-parent means for 20 oat populations. In th populations studied by Cowan and Frey (1987), the m parent mean generally was higher than the progeny m Predicting the genetic variance within a bipare population is more difficult and less reliable than pre ting the population mean. The coefficient of parent (Kempthorne 1969) has been suggested as one mea of genetic diversity. However, the coefficient of par age requires simplifying assumptions and quant only the probability of two alleles being identica descent. Breeders are perhaps more concerned wit probability of two allelles being alike in state, beca the genetic variance among progeny would be de mined by the number of alleles that are alike in sta The association between the genetic variance measures of genetic diversity among the parents been evaluated. Souza and Soorrells (1991) determ that the coefficient of parentage was a better predict genetic variances than similarity indexes derived f discrete morphological or biochemical markers. Cow and Fry (1987) found a significant correlation (r = 0 between the log of the generalized genetic variance genealogical distance. Cox et al. (1985a) suggested that the ideal bree population should have a high mean for the trai