Evaluating the interaction between genotype and water stress in the hybrid poplar – Septoria musiva pathosystemThis note is one of a selection of papers published in the Special Issue on Poplar Research in Canada.

Abstract

Septoria musiva , the causal agent of Septoria canker, has caused widespread damage to plantations of hybrid poplar across North America. A greenhouse experiment was conducted to evaluate the size of interactions between the genotype factors of (i) clone, (ii) isolate, and (iii) the clone–isolate interaction and the environmental factor of water stress. Four clones of hybrid poplar were inoculated with four isolates of S. musiva and subsequently exposed to two levels of water stress (stressed and unstressed). Tree height, root collar diameter (RCD), and disease severity were measured 56 d after inoculation. Water stress reduced height and RCD growth by approximately 30% but did not affect disease severity (P = 0.258). Of the explained variability, 97.5% was attributable to genotype effects (89% from clone, 0% from isolate, and 8.5% from clone–isolate interaction). The remaining 2.5% of the variation was accounted for by the genotype – water stress interaction. These results suggest that clonal effects will be more important determinants of disease severity under greenhouse conditions than genotype – water stress interactions.