Impact of Azadirachtin on Glomus Intraradices and Vesicular–arbuscular Mycorrhiza in Root Inducing Transferred Dna Transformed Roots of Daucus Carota

Abstract

Abstract-The impact of azadirachtin, neem extracts, and their products, Eneem 3G and Neemix 4.5E, on the symbiotic vesiculararbuscular mycorrhizal fungus Glomus intraradices was assessed by short-term subacute toxicity tests using root inducing transferred DNA (Ri T-DNA) transformed roots of Daucus carota as the host in the minimal medium system. The concentration causing 50% inhibition of growth and development was determined, and effects of these test materials on carrot roots and colonization by G. intraradices were also evaluated. The inhibitory effect of azadirachtin and neem compounds was compared with that of several reference pesticides (benomyl, chlorothalonil, copper sulfate, dimethoate, glyphosate, and its metabolite aminomethyl-phosphonic acid). Azadirachtin, neem extracts, Eneem 3G, and Neemix 4.5E, including their carriers and solvents, have low short-term toxicity to G. intraradices when compared with reference pesticides. As well, neither D. carota nor the vesicular-arbuscular mycorrhizal colonization was affected by these compounds. The potential ecotoxicological impact of azadirachtin, a new botanical insecticide, on the terrestrial environment is evaluated and discussed.

The effects of agricultural practices on arbuscular mycorrhizal fungi

“…a weed species), otherwise their effects on the AMF remain limited (Dodd & Jeffries 1989b;Allen & West 1993;Mujica et al 1999). Insecticides and nematicides cause much less damage to the AMF than benomyl and other fungicides (Wan & Rahe 1998). Some insecticides may cause transient decrease in root colonization, hyphal and spore densities in soil, whereas others such as monocrotophos usually promote root colonization of plants such as sorghum (Vijayalakshmi & Rao 1993), probably through decreasing the activity of hyphae-feeding nematodes and/or by improving the health of the host plants.…”

Impact of azadirachtin on Glomus intraradices and vesicular‐arbuscular mycorrhiza in root inducing transferred dna transformed roots of Daucus carota

“…Growth in length of Ri tDNA‐transformed carrot roots in the minimal medium is triphasic [24]. Typically, roots grow slowly 1 week after inoculation, then elongate rapidly from 2 to 4 weeks, and reach a stationary phase after 5 weeks.…”

“…The formation of mycorrhizae in Ri tDNA‐transformed carrot roots by G. intraradices averaged about 20% in 4‐week‐old cultures [24]. Acetone (6C) and methanol reduced ( p > 0.05) VAM colonization of carrot roots at 50,000 ppm when compared with controls.…”

“…The system was selected for this study because of its convenience, reliability, reproducibility, and novelty. It consists of self‐propagating mycorrhized Ri tDNA‐transformed roots of D. carota growing in sterilized minimal medium, which contains various salts, vitamins, sucrose, and water solidified with 0.4% (w/v) gellan gum (ICN Biomedical, Cleveland, OH, USA) in a petri dish as described by Becard and Fortin [23] and Wan and Rahe [24]. The roots serve as the host symbiont for the VAM fungus G. intraradices , and the plated minimal medium serves as a source of nutrients for the roots and a medium for colonization by the fungus.…”

“…Their responses to the inhibitory effects of each test compound at 2 weeks when compared with those of the water or solvent/carrier controls were used for the IC50 estimation. The measurement of EMG, EMS, and Ri tDNA‐transformed carrot roots was conducted by using the grid method [24,25]. The bioassay of each test material was repeated three times.…”