Final Results of Propagation Experiments to Show Distribution of Noninfectious Bud-failure in `Carmel' Almond

Abstract

The distribution of the potential for noninfectious bud-failure (BFpot) was shown for the entire `Carmel' almond cultivar by propagating from single buds on single budsticks on individual trees of separate source blocks of commercial nurseries. Approximately 2700 progeny trees were grown at the same test site. The gradual increase in the expression of BF (Bfexp) in progeny trees from individual source trees shows a continuous range of latent BFpot among individual source trees directly correlated to five (or six) consecutive generations of vegetatively propagated source orchards. This pattern shows a continuous gradient in expression (vertical variation). A continuous gradient in expression also exists among progeny trees originating from the same source tree (horizontal variation). Individual source trees were identified whose progeny produced little or no BFexp when grown for 5 or more years in a high temperature test site. These studies confirm that noninfectious bud-failure (and probably other genetic disorders) represent persistent variants of a specific gene(s) whose genepot changes during vegetative growth sequences to bring about differential expression over time (“age”) and developmental patterns. These represent a class of clonal variants which are “age-related” and include “phase changes”, “juvenility–maturity” phenomena, and can affect morphology, thorniness, ease of rooting, etc. BF is related to a gene that affects environmental adaptation of the almond. Control is through the selection, maintenance and management of foundation clones.