Consultant, Arboricultural Expert and Walnut and Chestnut Specialist

Le Sorpt

19600 Chasteaux

09 70 35 66 26

GRAFTING AND PROPAGATION TECHNIQUES

Micropropagation of walnut and chestnut trees

Why?

Rapidly reproduce the same healthy and efficient strains of these 2 species to obtain rootstocks resistant to the different pathogens that can lead to their early decay, increasing their strength and their productivity, as well as direct varieties on their own roots in some cases.

Micro cuttings cultivation phase:

It is done by sampling preferably carried out from March to June on reactive herbaceous shoots from young trees that are cut off to force the offshoot and growth

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In-vitro rooting phase :

In general, in-vitro rooting is carried out in 2 steps:

  • An induction phase on a gelose medium with auxins that boosts root initiation
  • A phase called root expression on another highly aerated gelose medium to boost root elongation
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Acclimatization in greenhouse phase:

Acclimatization in greenhouses is very delicate to handle, and it is necessary to gradually control the conditions that come close to the outside conditions. Walnut is extremely sensitive at this stage of cultivation.

Breeding in nursery phase:

It is done by sampling preferably carried out from March to June on reactive herbaceous shoots from young trees that are cut off to force the offshoot and growth

Layering of grape vines

This is a specific technique developed in the 1950s by an engineer from Comptoir des Bois de Brive for the reproduction of the first INRA hybrid chestnut clones.

1 - Parent plants:

They must be planted in light, acid, soft soil, without an excess of moisture that can promote the formation of bad coaxed roots of the spaghettis types which do not grow well. The spacing between the plants must be 3m between the lines and 0.50 to 0.80 cm on the line, and rather tight in hedges. The subjects are folded down to 10 cm from the ground, ready to branch out.

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2. Layering:

The subjects should be developed from 25 to 30 cm, of the diameter of a pencil (or less) up to the herbaceous stage during May or early June depending on the region.

Realization phase:

Thin out the leaves at a height of 20 cm from the base of the shoots

Place a staple at the base of each shoot without tightening; the strangulation must take place naturally, gradually

Earth up with soft soil with a gutter type machine that throws soil like raindrops. The roots protrude out in July-August.

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3 - Breeding of marcottes:

Harvesting can begin as soon as the leaves fall in December, sometimes in January. Rooted shoots must be sorted into 3 categories according to the development of the root flounces of each one

Extra choice: very nice roots and bushy stems

1st choice: medium roots and stems

2nd choice: weak roots

The extra choice can be grafted in the same year in April; choices 1 and 2 must be transplanted 1 year in order to be viable and ensure correct root recovery. The extra choice must also be folded down if it is not grafted or grafted to the right height from 20 to 50 cm depending on its size.

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Semi green grafting of the chestnut tree

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Walnut grafting on the table

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Semi green cuttings of walnut and chestnut

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