1- Portainjertos 420 A Millardet and Grasset
2- Usual name of the rootstock
420 A MGt
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.