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The Importance of Grafting and Rootstock Selection for Fruit trees Joel Reich M.S. Colorado State University Extension Integrated Land and Garden Workshop.

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Presentation on theme: "The Importance of Grafting and Rootstock Selection for Fruit trees Joel Reich M.S. Colorado State University Extension Integrated Land and Garden Workshop."— Presentation transcript:

1 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

2 A little background 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

3 A little background 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”)

4 A little background 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

5 A little background 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…

6 A little background 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

7 A little background 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!

8 Photos courtesy of U. of Minn. Extension

9 A little background A little background… Nowadays, we can reap the benefits of hundreds of years of development work on clonal varieties of scions and rootstocks

10 The Take-Home Message If you are only paying attention to the scion, you are missing half of the story

11 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

12 Dwarfing Terminology Standard – Full-size tree Vigorous – approx. 80% of standard Semi-Vigorous – approx % of standard Semi-Dwarf – approx % of standard Dwarf – approx. 25% of standard Apple is the only crop that has rootstocks in all size classes

13 Seedling rootstock (standard) vs. M.9 (dwarf)

14 Photo courtesy of U. of Minn. Extension

15 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.)

16 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

17 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

18 Peach Rootstocks Seedlings – Lovell (most common in Palisade-area orchards) – Bailey (slightly more cold-hardy than others) – Halford (better on high pH soils)

19 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 – %, cold-hardy, FB resistant OHxF 333 – 50-60%, cold hardy, FB resistant OHxF 51 – 25-30%, cold hardy, FB resistant


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