Cross Breeding of Populus and Its Hybrids for Cold Resistance

Populus tomentosa was crossed with P. tremuloidis, P. grandidentata, P. alba×P. grandidentata and P. alba×Ulmus pumila in order to maintain its rapid growth and high wood quality and improve its resistance to cold. Two methods were used to increase the germination rate from 1. 5% to 41. 1% and the remaining rate from 1. 7% to 44. 2%. Forty crossing combinations were conducted and 2 744 hybrid seedlings were obtained. MX₄×P. grandidentata (G-1-58), MX₃×P. tremuloidis (T-44-60), MX₂×P. tremuloidis (l-13-87-37) and MX₂×(P. alba×P. grandidentata) were regarded as superior combinations after analysis and selection. Thirty seedlings of these combinations and 11 triploid seedlings identified by counting their chromosomes were selected as super plants.