The Importance of Rootstock Selection

Report
The Importance of
Grafting and
Rootstock Selection
for Fruit trees
Joel Reich M.S.
Colorado State University Extension
Integrated Land and Garden Workshop
March 6, 2012
A little background…
• First, you need to understand that just about
every tree fruit you have ever seen or eaten
was grown on a grafted tree.
• A grafted tree is comprised of two
components:
– Scion
– Rootstock
Graft Union
A little background…
• All tree fruit varieties, such as ‘Fuji’ apple, ‘Navel’
orange, ‘Bartlett’ pear and ‘Bing’ cherry are clones.
• They are the result of either:
– many generations of genetic recombination (“breeding”)
– a random mutation (“a sport”)
A little background…
• Once a desirable variety (genotype) has been
found, we want to stop all genetic changes so
we can keep growing the fruit we like.
• Examples:
– Breeding  ‘Honeycrisp’ apple, ‘Santa Rosa’ plum
– Sport  ‘Navel’ orange, ‘Pinot Blanc’ grape
A little background…
• Since seeds are the product of genetic
recombination (a.k.a. “sex”), we do not grow
fruit trees from seed because the resulting
trees would have a different “genotype” from
the mother plant, resulting in different and
almost always inferior fruit.
• Because of this, we grow clones…
A little background…
• Clones are made from a piece of tissue of the
desired variety
• This tissue (a twig or even just a bud) is
referred to as the “scion”
• It is difficult to get a scion to grow roots, so we
graft the scion onto an existing and
compatible root system
A little background…
• Initially, any seedling rootstock was used as an
adopted set of roots for our desired varieties…
• Then people noticed that some seedlings
made particularly good rootstocks…
– Disease-resistant, cold- and/or drought-hardy,
precociousness, dwarfing.
• So we started cloning good rootstocks, too!
Photos courtesy of U. of Minn. Extension
A little background…
• Nowadays, we can reap the benefits of
hundreds of years of development work on
clonal varieties of scions and rootstocks
The Take-Home Message
• If you are only paying attention to the scion,
you are missing half of the story
What we (hope to) get from a Rootstock
• Control tree growth & size
• Promote earlier fruit production (precocity)
• Disease & insect resistance
– Fire Blight, Phytophthora, Verticillium
– Wooly apple aphid, nematodes
• Adaptation to different soil conditions
• Adaptation to different climates
Dwarfing Terminology
•
•
•
•
•
Standard – Full-size tree
Vigorous – approx. 80% of standard
Semi-Vigorous – approx. 60-70% of standard
Semi-Dwarf – approx. 40-50% of standard
Dwarf – approx. 25% of standard
• Apple is the only crop that has rootstocks in all
size classes
Seedling rootstock (standard) vs. M.9 (dwarf)
Photo courtesy of U. of Minn. Extension
Apple Rootstocks
• M.27 – 15-20% dwarfing (3-4’) very compact bush,
poorly anchored
• M.9 – 25-30% dwarfing (8’), susceptable to FB
• Bud 9 – 25-30% dwarfing (8’), FB resistant, very cold
hardy*
• G.16 – 25-30% dwarfing (8’), strong FB resistance*
• M.26 – 40-50% dwarfing (10’) very common, disease
probs.
• G.11 – 40-50% dwarfing (10’) strong FB resistance*
• G.30 – 50-60% dwarfing (12’) very cold hardy, FB
resistance
• M.7 – 55-65% dwarfing (12-14’) good FB resistance, not
super cold hardy)*
• MM.106, 14-18’(adaptable to many soils, FB probs.)
Cherry Rootstocks
• Gisela 5 – 50% dwarfing, sweet cherry, very
precocious, good availability
• Gisela 12 – 70% dwarfing, sweet cherry,
precocious, limited availability
• Gisela 6 – 80% dwarfing, sweet cherry, good
availability
• Mahaleb – 90% dwarfing, best stock for tart
cherry, drought and cold hardy
• Mazzard – 100%, best full-size for sweet cherry,
also used for tart where soils are heavy and/or
wet
Plum Rootstocks
• Myrobalan – 100%, strong, well-anchored.
Adapted to diverse soils
• Pixy – 60% dwarfing (about 9-10’), small fruit
• Krymsk 1 – 50% dwarfing (about 8’), very
cold-hardy, precocious, big fruit
• PumiSelect – 30-50% dwarfing, not
compatible with all varieties, Prunus pumila
Peach Rootstocks
• Seedlings
– Lovell (most common in Palisade-area orchards)
– Bailey (slightly more cold-hardy than others)
– Halford (better on high pH soils)
Pear Rootstocks
• Bartlett seedling – 100%, most common pear
stock worldwide
• Provence Quince – 50-65% dwarfing, high
yielding, adapted to calcareous soils, winter
tender, FB probs.
• OHxF 97 – 90-100%, cold-hardy, FB resistant
• OHxF 333 – 50-60%, cold hardy, FB resistant
• OHxF 51 – 25-30%, cold hardy, FB resistant

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