Field performance of Populus expressing somaclonal variation in resistance to Septoria musiva

Over 1500 trees from two hybrid poplar clones regenerated from tissue culture and expressing somatic variation in leaf disease resistance in a laboratory leaf disk bioassay were field-tested for 5-11 years to examine their resistance to Septoria leaf spot and canker and to assess their growth characteristics compared with the source clones. Somaclones expressed a wide range of disease reactions and growth rates. Generally, the leaf disk bioassay did not predict the resistance of the trees to stem cankers in the field; however, several selected somaclones outperformed the source clones. Results from this study indicate that somaclonal selection for desirable tree traits, such as disease resistance in Populus, may be feasible if a highly effective selective bioassay can be employed and if the trait is stable in the field. Cell and tissue culture conditions themselves apparently increased the growth rate of some of the regenerated trees compared with the source clones. At this time the cause of the random variation in disease resistance and tree growth is unknown and obtaining disease resistance in Populus using somaclonal selection is difficult and unpredictable. Published by Elsevier Science Ireland Ltd.