It looks like anthracnose disease caused by fungus, Colletotrichum orbiculare . The main symptoms are - appearing of jagged lesions near leaf veins. This lesions are dark brown to black in color with ‘shot hole’ appearance. Warm wet weather favors disease infection and spread.

Management:
1. Use certified healthy seeds for sowing.
2. Grow available resistant varieties.
3. Follow crop rotation (at least for 3 years).
4. Use drip irrigation instead of sprinklers.
5. Till the crop residue after cropping season.
6. If disease is severe spray fungicides like Mancozeb (2g/lit) or Copper hydroxide (2g/lit).