Effect of nitrogen fixing bacteria and moringa leaf extract on fruit yield, estragole content and total phenols of organic fennel

Abstract

The pharmaceutical manufacturer demand of organic medical and aromatic plants has strongly increased during the past decade. Therefore, using biostimulants to improve plant growth is a key factor in organic agriculture. The efficiency of three strains of nitrogen-fixing bacteria (NFB), two concentrations of moringa leaf extract (MLE) and their combinations have been evaluated on fennel plant growth, yield, and oil components. Plant height, branch number per plant, herb fresh weight, fruit weight, umbel number per plant, and fruit yield were significantly enhanced with the application of NFB and/or MLE. Photosynthetic pigments, total phenols, and oil components were also improved. The formation of the undesirable oil component, estragole, has been inhibited simultaneously with an increase in trans-anethole with the application of NFB, particularly Bacillus polymyxa (NFB1). Contrary, estragole content was dominant, in comparison to trans-anethole, with the MLE application. In this regard, the most pronounced effect was noticed with the combined application of Azotobacter chroococcum (NFB2) and MLE2. It could be concluded that using NFB as a biofertilizer without MLE is recommended for organic fennel production, in terms of fruit yield and oil quality.