Biological Control of Meloidogyne incognita by Aspergillus niger F22 Producing Oxalic Acid

Abstract

Restricted usage of chemical nematicides has led to development of environmentally safe alternatives. A culture filtrate of Aspergillus niger F22 was highly active against Meloidogyne incognita with marked mortality of second-stage juveniles (J2s) and inhibition of egg hatching. The nematicidal component was identified as oxalic acid by organic acid analysis and gas chromatography-mass spectroscopy (GC-MS). Exposure to 2 mmol/L oxalic acid resulted in 100% juvenile mortality at 1 day after treatment and suppressed egg hatching by 95.6% at 7 days after treatment. Oxalic acid showed similar nematicidal activity against M. hapla, but was not highly toxic to Bursaphelenchus xylophilus. The fungus was incubated on solid medium and dried culture was used for preparation of a wettable powder-type (WP) formulation as an active ingredient. Two WP formulations, F22-WP10 (ai 10%) and oxalic acid-WP8 (ai 8%), were prepared using F22 solid culture and oxalic acid. In a field naturally infested with M. incognita, application of a mixture of F22-WP10 + oxalic acid-WP8 at 1,000- and 500-fold dilutions significantly reduced gall formation on the roots of watermelon plants by 58.8 and 70.7%, respectively, compared to the non-treated control. The disease control efficacy of the mixture of F22-WP10 + oxalic acid-WP8 was significantly higher than that of a chemical nematicide, Sunchungtan (ai 30% fosthiazate). These results suggest that A. niger F22 can be used as a microbial nematicide for the control of root-knot nematode disease.

Screening, isolation and evaluation of a nematicidal compound from actinomycetes against the pine wood nematode, Bursaphelenchus xylophilus

“…The presence of vacuoles was previously reported in Meloidogyne incognita , known to cause root‐knot disease in plants, and B. xylophilus treated with iodoindoles . Those reports described severe morphological variations in M. incognita following treatment with oxalic acid, which showed complete destruction of internal organs, and the death of B. xylophilus caused by 5‐iodoindole was thought to be attributed to the increased vacuolisation by methuosis, as some of these compounds can destroy the nematode's physical barrier or tissues . We observed similar morphological changes in the B. xylophilus treated with spectinabilin.…”

Activity profiling of barley vacuolar processing enzymes provides new insights into the plant and cyst nematode interaction

“…The most visible feature in cells undergoing methuosis is the accumulation of fluid-filled cytoplasmic vacuoles derived from macropinosomes (Maltese and Overmeyer, 2014). Similar formation of vacuoles in nematode bodies was recently described for Meloidogyne incognita exposed to oxalic acid (Jang et al, 2016) and in Bursaphelenchus xylophilus incubated in 5-iodoindole (Rajasekharan et al, 2017). In both cases, morphological variations in the internal organs of treated nematodes and formation of vacuoles/granules and large voids within nematode bodies occurred, which are similar to the morphological alterations in H. filipjevi pre-parasitic juveniles treated with kalata B1.…”

Biological Control of Root-Knot Nematodes by Organic Acid-Producing Lactobacillus brevis WiKim0069 Isolated from Kimchi

“…Kojic acid produced by Aspergillus oryzae showed nematicidal activity against M. incognita (Kim et al, 2016). Among the A. niger culture metabolites, citric and oxalic acids were also demonstrated to have nematicidal activity (Jang et al, 2016; Zuckerman et al, 1994). Specifically, oxalic acid destroys internal bodies in M. incognita and produces numerous vacuoles in the nematode body.…”