black leg of basil

Black leg-Dark lesions can be seen on the lower stem of plants resulting in the decline of the plant. The symptoms shown here are from a hydroponic operation. 

Figure 1. Black leg of basil. Note dark necrosis of lower stems in hydroponic system. Figure 1. Black leg of basil. Note dark necrosis of lower stems in hydroponic system.
Figure 2. Black leg of basil. Figure 2. Black leg of basil.
Figure 3. Black leg of basil. Figure 3. Black leg of basil.