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.

Bioefficacy of novel cyanobacteria-amended formulations in suppressing damping off disease in tomato seedlings.

Biological control of plant pathogens is receiving increasing relevance, as compared to chemical methods, as they are eco-friendly, economical and indirectly improve plant quality and yield attributes. An investigation was undertaken to evaluate the potential of antagonistic cyanobacteria (Anabaena variabilis RPAN59 and A. oscillarioides RPAN69) fortified formulations for suppressing damping off disease in tomato seedlings challenged by the inoculation of a fungal consortium (Pythium debaryanum, Fusarium oxysporum lycopersici, Fusarium moniliforme and Rhizoctonia solani). Treatment with A. variabilis amended formulations recorded significantly higher plant growth parameters, than other treatments, including biological control (Trichoderma formulation) and chemical control (Thiram-Carbendazim). The A. variabilis amended compost-vermiculite and compost formulations exhibited 10-15 % lower disease severity and 40-50 % higher values than chemical and biological control treatments in terms of fresh weight and height of the plants. In future, in depth analyses regarding the mechanism involved in biocontrol by cyanobacteria and evaluation of these formulations under field conditions are proposed to be undertaken.

Effect of salt, drought and metal stress on essential oil yield and quality in plants.

Essential oil extracted from plants is of high commercial value in medicine, cosmetics and perfumery. Enhancing yield and maintaining the quality of oil is of significant commercial importance. Production of oil in plants is dependent on various biotic and abiotic factors to which the plants are subjected during their growth. Plants are exposed to various degrees of stress on account of natural and human-induced factors. Salinization, drought and presence of heavy metals in the substratum cause substantial effect on the yield and quality of bioactive constituents in the oil. In many plants, the level and kind of stress have detrimental effects on the growth and development. This review provides an account of the studies on some common abiotic stresses to which essential oil plants are exposed during their growth period and their influence on quality and quantity of oil. The yield and quality vary in different plants and so is the response. Enhancing essential oil productivity is an important challenge, and understanding the role played by stress may offer significant advantages to the essential oil farmers and processing industry. Scientific evaluation of the data on many important but unexplored essential oil plants will also help in mitigating, ameliorating and minimizing the harmful effects caused by stress.