1- Portainjertos 420 A Millardet and Grasset

2- Usual name of the rootstock

420 A MGt

3- Breeder

Alexis Millardet and Charles de Grasset

4- Year of obtaining


5- Genetic origin

It is a cross between Vitis berlandieri and Vitis riparia.

6- Resistance to soil parasites

420 A MGt offers a high degree of tolerance to root phylloxera.

It is resistant to the nematodes Meloidogyne incognita and Meloidogyne arenaria.

7- Adaptation to the environment

  • The 420 A MGt rootstock resists up to 35% total limestone , 20% active limestone and a CPI of 40.
  • The rootstock resistance to iron chlorination is medium to good.
  • The rootstock fertilization conditions are good in sufficiently deep calcareous soils, with sufficient hydration.
  • It is not adaptable in compact soils with excessive humidity conditions.
  • This rootstock has difficulty absorbing potassium from the soil.
  • The different varieties of grafts, in viticulture, can frequently present symptoms of potassium deficiency.

8- Interaction with the variety and production objectives

  • The vigor transmitted by the rootstock is low and the vegetative development of strains is limited.
  • However, it tends to retard maturity .
  • The 420 A MGt is prone to flower initiation.
  • 420 A MGt works well in viticulture with varieties such as Cabernet Franc N, Merlot N and Tannat.
  • The clones selected in the viticulture of the 420 A MGt standard are: 10, 11, 169, 241 and 758.

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