Persistence of azadirachtin‐a in two biological systems used for culturing mycorrhizal fungus Glomus intraradices
Abstract The disappearance of azadirachtin‐A (AZA‐A) was determined in the growth substrates of two biological systems in which one contained a gellan gum‐based minimal medium (M‐medium), and the other was vermiculite. AZA‐A degradation in these media followed pseudo‐first order kinetics. The half‐life of technical AZA‐A was 44.4 days in the M‐medium system, which contained mycorrhizal fungus Glomus intraradices growing on Ri T‐DNA transformed roots of Daucus carota. In the vermiculite system, which contained the same species of symbiotic fungus growing on the roots of Allium porrum, the half‐lives ranged from 13.2 to 46.2 days for technical and formulated AZA‐A. There was evidence to suggest the occurrence of unidentified AZA‐A conversion products in the treated and aged substrates of the two systems, as well as the presence of AZA‐B residues in products formulated with natural neem extracts. The persistence of AZA‐A in these biological systems is discussed in the context of using them to evaluate the no...