Influence of phosphorus and pH on the fungicidal potential of Anabaena strains

The genus Anabaena is known to be a rich source of bioactive metabolites, but the biocontrol potential of this genus, mediated through hydrolytic enzymes is less investigated. In our investigation, five Anabaena strains - A. laxa RPAN8, A. iyengarii RPAN9, A. variabilis RPAN59 and A. oscillarioides RPAN69 (with A. variabilis RPAN16 serving as negative control) were evaluated in time course studies involving incubation under three levels of phosphorus and pH conditions. Total chlorophyll, proteins, chitosanase, endoglucanase and CMCase activity were measured and inhibition assayed against phytopathogenic fungi. The four weeks old RPAN69 culture showed significantly higher chlorophyll which was 41% higher than control. This was also linked with an enhancement of 18.26% and 9.18% in chitosanase and CMCase activity respectively over control in the treatment involving half dose of phosphorus. Chlorophyll and CMCase activity showed a high degree of correlation with highest values at pH 9.5. A pH of 5.5 was the most suitable condition for the maximum activity of chitosanase for all the strains except RPAN16. The strains RPAN8 and RPAN9 showed the highest activity of endoglucanase at pH 5.5 while the other strains exhibited maximum activity at pH 7.5. This study provides insight into the role of P and pH in modulating fungicidal activity in different Anabaena strains, which can be valuable for enhancing their efficiency as a biocontrol agent.