In defense of the polycross

In Pinaceae species, except for Tsuga, the small number of pollen grains that actually compete in the generative process limits the possible reproductive bias that can result from using the polycross mating design for estimating genetic parameters. For species in which the number of competing pollen grains is 3 or less and where the number of males represented in the pollen mix is 20 or more, reproductive bias is within acceptable limits even if one male were to be favored over all others. Reproductive bias in other species, or where less than 20 males are represented in the mix, can be effectively reduced by diluting the pollen mix with dead pollen.