One-way crossing barriers in some interspecific crosses of Aigeiros and Tacamahaca poplars

摘要

Artificial interspecific crosses were tried between Populus balsamifera and P. maximowiczii (section Tacamahaca), P. deltoides and P. nigra of section Aigeiros, and the interspecific hybrids P. X euramericana (P. deltoides X P. nigra) [P. canadensis] and P. X jackii (P. balsamifera X P. deltoides). The parent trees for the crosses were mature specimens growing in Ontario, Canada. Crosses with P. balsamifera or P. nigra as the female parent, and P. maximowiczii as the male parent could be saved onlywith the help of embryo culture. The other crosses with P. maximowiczii as the male parent showed variable success. Crosses in the opposite direction with P. maximowiczii as the female parent generally succeeded, except that with P. deltoides which could only be rescued with embryo culture. Crosses of P. deltoides X P. jackii were of variable success, depending on the individual trees involved. Crosses of female P. nigra with all other species failed. The possible genetic mechanisms underlying the one-way crossing barriers between sections are discussed.