RELATIONSHIPS AMONG EUROPEAN BARLEY GERMPLASM .2. COMPARISON OF RFLP AND PEDIGREE DATA

Information about the genetic relationships among genotypes is of grea t importance to breeders of barley (Hordeum vulgare L.) and other self -pollinated crops. In the past, genetic similarity was mainly estimate d by Malecot's coefficient of coancestry (f). However, estimates of f may not always reflect the true relationship between genotypes because of selection, random genetic drift, and other causes. In this study, we analyzed 24 winter and 24 spring barley cultivars from the European barley germplasm by means of restriction fragment length polymorphism (RFLP) and pedigree analyses. Our main objective was to compare genet ic similarity (GS) based on RFLP data of 136 clone-enzyme combinations (CEC) with coancestry (f) for their ability to quantify the degree of relatedness among barley genotypes. Rank correlations between GS and f for related (f greater than or equal to 0.10) pairs of cultivars wer e weak for both winter (r(s) = 0.21) and spring barley cultivars (r(2) = 0.42). Based on linear regression of GS on f, coancestry explained 6 and 14% of the variation in GS for related (f greater than or equal to 0.10) pairs of winter and spring barley cultivars, respectively. Th e weak correlations can be explained primarily by (i) unrealistic assu mptions in calculation off and (ii) substantial variation in GS estima tes of unrelated cultivars. In conclusion, coancestry seems less suite d than RFLP-based GS estimates to quantify the genetic relationships a mong barley cultivars for many applications in breeding.