ARS | Publication request: Potential of Neoactinolaimus as a biological control agent of root-knot and reniform nematodes

Submitted to: Society of Nematologists Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 21, 2012
Publication Date: N/A

Technical Abstract: The predatory nematode Neoactinolaimus spp. (family Actinolaimidae) was examined as a potential biological control agent against root-knot (Meloidogyne spp.) and reniform (Rotylenchulus reniformis) nematodes in laboratory conditions. Neoactinolaimus possesses a large odontostylet to puncture the cuticle of its nematode prey and feed on their contents. Neoactinolaimus was selected for this experiment due to the high abundance recovered from the rhizosphere of Hawaiian native sedge, 'Ahu'awa Cyperus javanicus. In vitro cultures were established on quarter strength corn meal agar (CMA/4) containing carrot discs and bacterial feeding nematodes dominated by Rhabditidae as prey. The reproductive rate of Neoactinolaimus in this CMA/4 culture varied from 0 to 16 nematodes/month. An in vitro assay was conducted using soil nematodes extracted from a field previously planted in cantaloupe (Cucumis melo) and highly infested with root-knot (Meloidogyne incognita and M. javanica) and reniform (Rotylenchus reniformis) nematodes. Soil was extracted using an elutriator and the centrifugal flotation method. All nematodes extracted were identified to genus level and counted before and 6 days after the introduction of 16 Neoactinolaimus per beaker. Five replicated beakers were used. The Neoactinolaimus were then picked and frozen for molecular gut analysis using multiplex PCR primers targeting the ITS region of Meloidogyne spp. and R. reniformis. The experiment was repeated once. Assuming that all the nematodes that disappeared 6 days after inoculation was due to the feeding of Neoactinolaimus as no other nematode predators were present in the beakers except omnivorous nematodes, Neoactinolaimus suppressed 60% and 48% of the population of Meloidogyne spp. and R. reniformis, respectively in Trial I; and suppressed 34% and 61%, respectively in Trial II. Suppression of bacterivores, fungivores, herbivores and omnivores by Neoactinolaimus were 76, 21, 87, and 81%, respectively in Trial I; and were 54, 51, 48, and 78%, respectively in Trial II. Confirmation of the feeding on Meloidogyne spp. and R. reniformis by Neoactinolaimus using multiplex PCR analysis is in progress. Further research is needed on culture media that can support more consistent reproduction of Neoactinolaimus, and an in vivo assay on suppression of Meloidogyne spp. and R. reniformis by Neoactinolaimus.