Validation of an Alternative Small Stem Assay for Blight Resistance in Chestnut Seedlings and Recommendations for Broader Use.

We evaluated an alternative small stem assay (AltSSA) for blight resistance in backcross hybrid chestnut trees (). Whereas standard small stem assays (SSAs) are done by inoculating small incisions in stems, in our AltSSA, 4- to 5-mm stems are cut off, and the exposed (living) stem tips are inoculated with discs of inoculum and temporarily covered with plastic sleeves. Intended primarily for forward selection, this method was designed to be easy to implement, to consistently induce cankering, and to better enable seedling recovery via the development of lateral shoots from the lower stem.