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ARS Home » Pacific West Area » Davis, California » Nat'l Clonal Germplasm Rep - Tree Fruit & Nut Crops & Grapes » Research » Publications at this Location » Publication #311024

Research Project: Management of Genetic Resources & Associated Information for Grape, Tree Fruit, Tree Nut, & Other Specialty Crops to Mediterranean Climates

Location: Nat'l Clonal Germplasm Rep - Tree Fruit & Nut Crops & Grapes

Title: Propagation of almond rootstocks and trees

Author
item Preece, John
item Debuse, Carolyn

Submitted to: Review Article
Publication Type: Other
Publication Acceptance Date: 4/25/2014
Publication Date: N/A
Citation: N/A

Interpretive Summary: Millions of almond trees in production in California and elsewhere were propagated by nurseries using the grafting technique called budding. This gives a uniform orchard and allows the grower to select nut cultivar (scion) and rootstock combinations. Grafting is a form of clonal propagation and results in genetically uniform plants. The cultivar ‘Nonpareil’ is an example of a clone or clonal population that can be traced back to the original tree that A. T. Hatch of Suisun, CA selected from a group of 200 seedlings he planted in 1879. Because they were propagated vegetatively every ‘Nonpareil’ tree is a member of that clone. Commercial almond cultivars are not propagated by seed because they are heterozygous containing both dominant and recessive genes for many traits, including bitterness. This heterozygous genetic condition results in them not coming “true” from seed. However, even if they did come true, because of juvenility, seedlings typically require 4-7 years to reach maturity and begin flowering, slowing production. Therefore almonds are propagated vegetatively to ensure uniformity, productivity, quality, flowering and harvest dates, nut and tree characteristics, and cultivar identification. Almond cultivars are budded or grafted onto seedling or clonal rootstocks. Rootstocks are important to growers for the adaptability, disease resistance, and productivity that they impart to the tree on a specific site. Seeds for the seed-propagated rootstocks must be harvested and extracted from fruit. They are then stratified, germinated, and grown to sufficient size for budding or grafting. Clonal rootstocks may be propagated by rooting cuttings or micropropagation (tissue culture). Similar to seedlings, clonal plants must be grown to sufficient size for budding and grafting. Budding and grafting require making proper cuts on the scion material and rootstock. The cutting and alignment of the graft or bud union and time of year are equally important to ensure grafting success. Typically, budded plants are propagated and grown in the nursery then sold for planting into production orchards. Grafting is primarily used for changing the cultivar of established trees in a process called topworking. Saw-kerf (wedge), cleft, and bark grafts are used for topworking.

Technical Abstract: Millions of almond trees in production in California and elsewhere were propagated by nurseries using the grafting technique called budding. This gives a uniform orchard and allows the grower to select nut cultivar (scion) and rootstock combinations. Grafting is a form of clonal propagation and results in genetically uniform plants. The cultivar ‘Nonpareil’ is an example of a clone or clonal population that can be traced back to the original tree that A. T. Hatch of Suisun, CA selected from a group of 200 seedlings he planted in 1879. Because they were propagated vegetatively every ‘Nonpareil’ tree is a member of that clone. Commercial almond cultivars are not propagated by seed because they are heterozygous containing both dominant and recessive genes for many traits, including bitterness. This heterozygous genetic condition results in them not coming “true” from seed. However, even if they did come true, because of juvenility, seedlings typically require 4-7 years to reach maturity and begin flowering, slowing production. Therefore almonds are propagated vegetatively to ensure uniformity, productivity, quality, flowering and harvest dates, nut and tree characteristics, and cultivar identification. Almond cultivars are budded or grafted onto seedling or clonal rootstocks. Rootstocks are important to growers for the adaptability, disease resistance, and productivity that they impart to the tree on a specific site. Seeds for the seed-propagated rootstocks must be harvested and extracted from fruit. They are then stratified, germinated, and grown to sufficient size for budding or grafting. Clonal rootstocks may be propagated by rooting cuttings or micropropagation (tissue culture). Similar to seedlings, clonal plants must be grown to sufficient size for budding and grafting. Budding and grafting require making proper cuts on the scion material and rootstock. The cutting and alignment of the graft or bud union and time of year are equally important to ensure grafting success. Typically, budded plants are propagated and grown in the nursery then sold for planting into production orchards. Grafting is primarily used for changing the cultivar of established trees in a process called topworking. Saw-kerf (wedge), cleft, and bark grafts are used for topworking.