STAGE 2 - STOOL PLANT SELECTION...
Stool Plant Selection: Individual rootstock genotypes are propagated as shrubs that are sheared at ground level, and a rooting medium (sawdust or other material) is mounded around the growing shoots to induce rooting. At the end of the season the genotypes that demonstrate non-brittle wood, adequate rooting, and few thorns or branches are selected for inclusion in the nursery. This genotype was not selected for further testing because it exhibits excessive branching and spines. Selected genotypes have been removed from this field for further testing.
Nursery Liner Establishment: Four to ten trimmed nursery liners from the individual stool trees have been recently planted in the nursery. Each genotype is tagged with its name, and a green flag has been inserted between genotypes. These trees will be budded with the scion cultivar Mutsu in August.
Nursery Tree Growth: Twenty months after planting the liners for an initial test orchard, these trees of Mutsu on a first test rootstock are ready to be dug and transplanted to the orchard trial. Our goal is to produce healthy, large caliper trees such as these for all our orchard trials.
Screening for resistance to fire blight in the initial stool tree field is performed by inoculating 3 shoots per plant with live cultures of a virulent strain of Erwinia amylovora bacteria. The yellow tags mark where a shoot that has been inoculated. The shoot pictured above has developed symptoms of fire blight 10 days after inoculation, and therefore will be eliminated from the program prior to any orchard trials. At this time, only genotypes that display complete resistance to infection as seedlings and as field-grown trees are retained in the Geneva breeding and evaluation program beyond stage 2.