Root-Knot Nematode Species Identified

By Sharon Durham
August 20, 2004

A root-knot nematode species, previously unnamed and assumed to be “race 3” of Meloidogyne incognita, has now been classified as its own species, M. floridensis.

The discovery is based on studies by an international team including scientists from the Agricultural Research Service (ARS) in Beltsville, Md., and Byron, Ga., Laboratoire de Biologie des Invertébrés in France, and Plant Research International in the Netherlands.

The newly named nematode was isolated from nematode-resistant Nemaguard and Okinawa peach rootstocks in Gainesville, Fla. This explains why nematodes were infesting and reproducing in these root knot nematode resistant rootstocks.

ARS plant pathologist Andrew Nyczepir, of the Southeastern Fruit and Tree Nut Research Laboratory in Byron, Ga., found the pest’s penchant for nematode-resistant rootstock uncharacteristic and formed the group to conduct various studies. Morphological, cytological, molecular and host-range studies conclusively determined the taxonomic position of the nematode.

Through the use of a scanning electron microscope, the team, led by ARS microbiologist Zafar Handoo of the Nematology Laboratory in Beltsville, Md., showed important physical differences between M. floridensis and M. incognita.

Nyczepir used host-range testing to determine that M. floridensis didn’t exhibit the same host affinities as M. incognita. For instance, M. floridensis reproduced abundantly on Nemaguard and Guardian peach rootstocks, whereby M. incognita does not. Alternately, M. floridensis doesn’t reproduce in peppers as M. incognita does.

Molecular studies confirm the uniqueness of M. floridensis from M. incognita and other root-knot nematodes.

ARS is the U.S. Department of Agriculture’s chief scientific research agency.