Progress in developing disease control strategies for hybrid poplars

Hybrid poplars are being grown throughout many regions of the world for purposes including the production of fiber and energy, ornamental landscape plantings, and soil stabilization. Disease has often been responsible for planting failures resulting in poplars being labeled the universal host to many damaging pathogens. However, many of the poplar species and their hybrids are not native to the areas where they are being planted and so they do not have resistance to the local pathogen populations they are exposed to. Currently research is aimed at detecting pathogenic variation in populations of fungi affecting poplars and in gaining knowledge of the underlying genetic mechanisms of disease resistance in poplars. Significant progress is being made in breeding for disease resistance and in developing poplar clones that are better adapted to the sites on which they are being planted. There is evidence that some phenological traits of clones such as time of leaf flush and leaf fail may be used to select clones that can escape peak periods of infection by some pathogens. Somaclonal selection, a tissue culture technique coupled with a laboratory bioassay, has been used to generate clonal fines of poplars with increased disease resistance that have performed well in field tests. A biorational approach to disease control using a common soil bacterium has shown promise in laboratory and field tests against several major poplar pathogens. Progress in the above areas of disease research will enable growers to plant productive, disease resistant hybrid poplar clones.