Wilted Basil (Fusarium Wilt)

A week ago I bought some sweet basil at the local nursery, planted it in a container and put it in full sun. I have kept the soil moist..and it has wilted down..what am I doing wrong?

The problem could be that during transplanting the soil got so disturbed that the roots sustained too much damage to be able to keep the plant supplied with sufficient water to remain turgid. After transplanting it is always a good idea to keep the repotted plant in a shady spot for a week or two to allow for root regrowth. If you have no shady spot, cover the plant with newspapers for a week or two instead.
The most likely reason for the wilting is an infection with the dreaded fusarium wilt that most basils are so susceptible to. The spores can stay alive in the soil and wait for a susceptible plant before spurting into growth, infecting the plant near the soil level and killing the tissue so that it cannot conduct any more water up the stem and the plant therefore wilts. You should be able to see a dark discoloured area just above the soil level on the stem.
Just as this disease started to destroy basil farms, a strain was discovered that is resistant to the wilt. It was named "Nufar F1" and is available from Richters. We would suggest that you grow only this strain, since you cannot get rid of the spores from the soil without baking the damp soil to at least 100 degrees Celsius for one hour- impractical for a garden!