Effect of witches' broom mutation on growth of Pinus sibirica seedlings

Mutational witches' brooms (WB) spontaneously arise in the tree crown. There are no male cones in Pinus sibirica WB and pollination always occurs with normal pollen. We studied 2-year-old seed progeny obtained from open-pollinated cones of WB and normal crown (NC) pines. There were significant morphological differences in two pairs of WB and NC families, while the third family pair studied showed barely pronounced differences. Segregation analysis of WB seed progeny based on needle length (growth trait) and total bud number (branching trait) revealed that about half of seedlings had a normal phenotype, while mutants were from 15.6 to 35.7 %. The rest seedlings could not be unambiguously identified, because they have not yet fully demonstrated the phenotype. Looking normal seedlings from WB families differed not only from mutants but also from NC progeny. Therefore, the mutation had some effect on both mutant seedlings and seedlings with a normal phenotype. Moreover, the denser was maternal WB the more differences were observed between WB and NC progeny.