Thinking and practices for strategy on a new round genetic improvement of Populus tomentosa.

In this paper, in view of the significant effects of social and economic changes on poplar demands, a new round of genetic improvement strategy for Populus tomentosa was proposed based on analyzing the current situation and problems in combination with thinking and practices on variety breeding. It is necessary to design appropriate breeding objectives for different cultivation areas and application requirements, especially to select male varieties with fast-growth, high-quality and high resistance for timber forest and landscape, as well as the varieties exhibiting strong resistances to cold, drought, high temperature and water. According to the climatic regionalization and genetic differentiation of the natural populations, it should not only enrich the existing gene pool in the south distribution area (Guanxian County, Shandong Province), but also establish a new one in the north distribution area. Thus effective sub-regional preservation and utilization of P. tomentosa genetic resources would be realized. To solve the problem that it is still not taking full advantage of maternal effect in P. tomentosa breeding, screening out female parents with good fertility and high general combining ability though the analysis of half-sib progenies in the gene pool, and identifying the male parents for the superior individuals using molecular markers should be conducted. Furthermore, building a parents group that is suitable to different breeding objectives though the comprehensive assessment on main traits and genetic diversity to produce new varieties of P. tomentosa allotriploid using the gametes chromosome doubling technique is feasible. Given the complex grafting technology, high-cost, and easy aging of the seedlings for P. tomentosa breeding, exploiting the rejuvenation of tissue culture plantlets and suckers, vessel and field hard-wood cutting will be a good way to fulfill low-cost, effective and quickly large-scale propagation for P. tomentosa.