Genetics of the polycross : 1. Experimental results from Norway spruce

Rates and patterns of male gamete incorporation for a polycross mating design were studied for two independent years of pollination in Norway spruce, Picea abies (L) Karst. Segregation distortion in a subset of maternal clones was documented for one locus. We have proposed a model, involving the existence of a linked lethal allele, which accounts for these observations. Significant temporal and maternal clonal differences were observed in the rates at which single locus and multilocus gametes were incorporated. Striking differences in apparent fertility existed among four clones which produced unique multilocus gametes. One clone, in particular, was shown to be contributing three times as many gametes to the next generation as predicted by the hypothesis of equal clonal male contribution. These deviations from expectation were also detected in the genotypic distributions of the resultant filial generation. Ramifications of these results on family structures in the filial generation, effective size of the male population, and possible bias in inferences of genetic differences and parameter estimation are discussed.