Genetic variation of RAPD markers in a Picea abies Karst population

We report the results of the screening of 20 mapped RAPD loci over haploid megagametophytes from 48 individual trees of an Italian population of Norway spruce. LOD scores for 190 pairs of loci were calculated over families of megagametophytes from `informative' trees, and linkage relationships between pairs of markers were analysed. Single-locus genotypes were inferred from haploid progeny-array data and were used to estimate linkage disequilibrium between loci. Significant deviations from equilibrium did not appear to be randomly distributed over loci. Most of the markers analysed showed an excess of heterozygotes and five out of 20 RAPD markers showed significant deviations from Hardy-Weinberg equilibrium. A weak spatial structure was detected by spatial autocorrelation at the scale considered (0-180 m), suggesting a lack of `family structure' arising from isolation by distance. Nonrandom distribution of the genetic variability was limited to some loci. Di- and tri-locus spatial autocorrelation of loci showing linkage disequilibrium was also carried out.