Usage of brown algae Padina pavonica and Turbinaria decurrens to control bacterial brown rot disease

      Brown algae contain the highest biological activities and considered an important source of bioactive natural substances. Two algae (Padina pavonica and Turbinaria decurrens) extracted by two solvent (water and ethanol) used to study their antibacterial activity on development brown rot disease in vitro and under artificial inoculation condition. The two algae (P.  pavonica and T.  decurrens) inhibited the growth of Ralstonia solanacearum in vitro. The highest inhibition zone recorded with P. pavonica water extraction and the least one was T. decurrens ethanol extraction. Two algae extraction decreased area under disease progress curve (AUDPC) and disease severity in all treatments compared with the positive control.  Quantity of total and free phenols increasing to reach high amount in P. pavonica water and ethanol extractions compared with T. decurrens extractions. The suppuration of R. solanacearum and its disease severity affected by the kind of extraction solvent used in the extraction of algae and the amount of total and free phenols for each alga.  Water and ethanol extraction of P. pavonica was more effectiveness in controlling R. solanacearum in vitro and under artificial inoculation condition. Further research aiming to identify the specific phenolic compounds which are responsible for higher antibacterial activity and availability of apply the algae in controlling plant diseases.