[nctomatoman]

So the best way to consider this is the absolute definition of resistance and tolerance.

Resistance means that the mechanism of the plant resists attack of the agent - in the case of Fusarium, a fungus that moves into the roots from the soil, a F resistant variety means that the roots resist movement of the agent into the roots.

Tolerance means that even though the agent moves into the plants, the plant can tolerate the attack and do reasonably well for a spell after attack.

But here's the thing - the terms are really relative and misinterpreted. In high disease pressure areas, plants won't resist or tolerate the disease indefinitely. For example, let's say you have a Fusarium resistant plant. The plant will resist the disease a bit longer than a non resistant plant, but if the disease pressure is high, it will go down a few weeks later (or some time frame).

So with grafts, if rootstock is highly resistant to this or that disease, in principal it will from some to alot more time. The key then is to use good garden hygiene, keep soil from splashing onto foliage above the graft line, etc - that plant top will be just as susceptible to the disease as an ungrafted plant - the protection is whatever the roots can provide.