PERSISTENCE OF AZADIRACHTIN-A IN 2 BIOLOGICAL-SYSTEMS USED FOR CULTURING MYCORRHIZAL FUNGUS GLOMUS INTRARADICES

The disappearance of azadirachtin-A (AZA-A) was determined in the grow th substrates of two biological systems in which one contained a gella n 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 infraradices 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 ro ots 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 occ urrence of unidentified AZA-A conversion products in the treated and a ged substrates of the two systems, as well as the presence of AZA-B re sidues in products formulated with natural neem extracts. The persiste nce of AZA-A in these biological systems is discussed in the context o f using them to evaluate the non-target effects of this compound on ve sicular arbuscular mycorrhizal symbiosis.