ALLOZYME EVIDENCE FOR POLYZYGOTIC POLYEMBRYONY IN SIBERIAN STONE PINE(PINUS-SIBIRICA DUTOUR)

Approximately 4000 mature seeds from 350 trees in nine populations (12 -75 trees per population) of Siberian stone pine were investigated for multiple embryos (polyembryony). Haploid megagametophytes and embryos were genotyped for eight allozyme loci. Eighty-one seeds (2.11%) had more than 1 embryo. Of these, 71 seeds had 2 embryos (1.85%), 6 seeds had 3 embryos (0.16%), 3 seeds had 4 embryos (0.08%) and 1 seed had 6 embryos (0.026%). Allozyme comparison of megagametophytes and embryos could distinguish two types of polyembryony in 56 of the 81 seeds. In 28 seeds (50%) the polyembryony was polyzygotic (independent fertiliza tions of more than one egg cell in the ovule); 25 seeds (45%) had most likely monozygotic polyembryony (genetically identical embryos result ing from the cleavage of a single proembryo) and 3 seeds had both gene tically different and genetically identical embryos. To the best of ou r knowledge, this is the first genetic evidence for the form of polyem bryony in conifer seeds.