Propagation from basal epicormic meristems remediates an agring-related disorder in almond clones

Authors: GRADZIEL, THOMAS - University Of California; LAMPINEN, BRUCE - University Of California; Preece, John

Submitted to: Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2019
Publication Date: 4/11/2019
Citation: Gradziel, T., Lampinen, B., Preece, J.E. 2019. Propagation from basal epicormic meristems remediates an agring-related disorder in almond clones. Horticulturae. 5(28):1-9. https://doi.org/10.3390/horticulturae5020028.
DOI: https://doi.org/10.3390/horticulturae5020028

Interpretive Summary: The asexual propagation of clonal crops has allowed cultivation of superior selections for thousands of years. With time, clones deteriorate from genetic and epigenetic changes. Noninfectious Bud-Failure (NBF) in cultivated almond (Prunus dulcis) is a commercially important age-related disorder that results in the failure of new vegetative buds to grow in the spring, dieback of terminal shoots, witches-brooming of surviving buds, and deformed bark (roughbark) The incidence of NBF increases with clonal age, including within individual long-lived trees as well as nursery propagation lineages. It is not associated with any infectious disease agents. Consequently, traditional nursery practices emphasize the establishment of foundation-mother blocks using propagation-wood selected from well-established and monitored propagation-lineages. Commercial propagation utilizes axillary shoot buds through traditional budding or grafting. An alternative source of foundation stock is basal epicormic buds from individual trees of advanced age. The age-related progression of NBF appears to be arrested in such epicormic meristems, possibly owing to their unique origins and ontogeny. NBF development in commercial orchards propagated from Foundation-blocks established from these sources was dramatically suppressed over the 10 to 20 year expected commercial orchard-life. Foundation-stock stability can be further maintained through appropriate management of propagation source-trees, which requires accurate knowledge of meristem origin and development.

Technical Abstract: The asexual propagation of clonal crops has allowed cultivation of superior selections for thousands of years. With time, clones deteriorate from genetic and epigenetic changes. Noninfectious Bud-Failure (NBF) in cultivated almond (Prunus dulcis) is a commercially important age-related disorder that results in the failure of new vegetative buds to grow in the spring, dieback of terminal shoots, witches-brooming of surviving buds, and deformed bark (roughbark) The incidence of NBF increases with clonal age, including within individual long-lived trees as well as nursery propagation lineages. It is not associated with any infectious disease agents. Consequently, traditional nursery practices emphasize the establishment of foundation-mother blocks using propagation-wood selected from well-established and monitored propagation-lineages. Commercial propagation utilizes axillary shoot buds through traditional budding or grafting. An alternative source of foundation stock is basal epicormic buds from individual trees of advanced age. The age-related progression of NBF appears to be arrested in such epicormic meristems, possibly owing to their unique origins and ontogeny. NBF development in commercial orchards propagated from Foundation-blocks established from these sources was dramatically suppressed over the 10 to 20 year expected commercial orchard-life. Foundation-stock stability can be further maintained through appropriate management of propagation source-trees, which requires accurate knowledge of meristem origin and development.