Thank you for your help
So I will try grafting a variety of sweet bell pepper and a variety of hot pepper on :
tomato rootstock Groundforce F1
tomato rootstock Arnold F1
Aji Amarillo
Rocoto
7 Pod Brain Strain
7 Pod Morouga Blend
Solanum torvum
Solanum capsicoides
Solanum mauritianum
Solanum aculeatissimum
It seems there is a real interrest to graft sweet bell peppers on hot pepper rootstock :
"Sweet peppers can be difficult to grow because their root systems are not as strong as those of many other pepper varieties. They are susceptible to flooding and a wide range of plants diseases. One way to "toughen them up" is to graft the sweet pepper you want onto a stronger, more disease-resistant rootstock, like chili pepper rootstock, which is not as prone to root rot and disease. This is a procedure most gardeners can perform themselves."
( http://www.ehow.com/how_7627137_graft-peppers.html )
But there are less evidences of the benefits of grafting hot peppers on rootstocks. The main interrests : creating one plant producing 2-3 varieties of peppers.
Anyway, I'll try and keep you informed.