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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.

The potential for noninfectious bud-failure in propagation source material for `Carmel' almond in California has been determined in progeny tests from commercial nursery sources. Percentage BF increased with time (temporal), but decreased in severity (spatial). Analysis of variability in nursery sources showed that the key to successful selection for low BF potential is the individual tree, although variability exists among nurseries, budsticks (within trees), and individual buds (within budsticks). One-half of the individual trees of the nursery population tested have produced BF progeny so far within the test period. Future BF from the remainder was project by a BF model to be beyond the critical economic threshold. Two low BF-potential single tree sources were identified for commercial usage and progeny tests have started on an additional 19.

Previously well irrigated mature `Nonpareil' almond trees (Prunus dulcis) were subjected to varying periods of water deprivation prior to harvest and then to either full or no postharvest irrigation. Eight preharvest water deprivation (PWD) lengths ranging from 14 to 63 days were evaluated on a sandy loam soil with a rooting depth of about 1.5 m.Development of tree water deficits occurred rapidly following PWD. Predawn leaf water potential decreased to about -1.8 and -3.1 MPa after 10 and 20 days, respectively. Defoliation began about 30 days after PWD and trees subjected to more than 50 days completely defoliated. The rate of hull split was directly related to the PWD duration. With early cutoffs, the size of the hull split-arrested nuts at harvest was large compared with the same nut type in later cutoffs suggesting that as nuts develop, large nuts are preferential sinks for assimilates. Kernel size was only mildly reduced by PWD during the first study year. There was a trend toward lower total kernel yield with longer PWD as a result of smaller kernel girth but yield differences were not significant. The number of nuts remaining in the tree after shaking was not related to PWD. Bark strength increased after PWD with 10 to 14 days required to prevent shaker damage. Postharvest irrigation resulted in late season defoliation but no rebloom. Bloom density reductions in 1990 were related more to the lack of 1989 postharvest irrigation than to early PWD.