April 16, 2005
Source: American Phytopathological Society, Plant Disease Notes [edited]

First report of the root-knot nematode Meloidogyne floridensis on tomato in Florida
GT Church, US Horticultural Research Laboratory, USDA-ARS, Fort Pierce, FL 34945. Plant Dis 2005; 89: 527, published online as DOI: 10.1094/PD-89-0527B. Accepted for publication 11 Feb 2005.

The state of Florida is the largest producer of fresh market tomato (_Lycopersicon esculentum_ L.) in the United States, with 2003 yields of 634 million kg on 17 700 ha, valued at USD 516 million. Effective crop management is essential for production of vegetables in Florida because of the presence of intense pest pressure. The identification of the pests present is the 1st step in the development of a successful IPM (integrated pest management) program.

Root-knot nematodes (_Meloidogyne_ spp.) are common nematodes that parasitize vegetables in Florida and cause significant yield reductions when not properly managed. In 2003 field experiments, soil was collected from 2 research farms in Saint Lucie and Seminole counties in Florida. Galling caused by root-knot nematode was observed on tomato at both locations. Since females suitable for identification are difficult to obtain from field-grown roots, field soil was placed in pots in the greenhouse and planted with _Lycopersicon esculentum_ cv. Rutgers.

Standard morphological techniques, differential host tests, and isozyme phenotypes were used in nematode identification. Female root-knot nematodes were extracted from tomato roots and placed in extraction buffer (10 per cent wt/vol sucrose, 2 per cent vol/vol Triton X-100, 0.01 per cent wt/vol bromophenol blue). The females were crushed, loaded on a polyacrylamide gel, and separated by electrophoresis using the PhastSystem (Amersham Biosciences, Piscataway, NJ). The activities of malate dehydrogenase and esterase enzymes were detected using standard techniques.

Isozyme phenotypes consistent with _Meloidogyne incognita_ (Kofoid and White) Chitwood and _M. javanica_ (Treub) Chitwood as well as with the newly described _M. floridensis_ Handoo (1) were observed at both locations.

To our knowledge, this is the 1st report of _M. floridensis_ naturally occurring on tomato in Florida. The identification and distribution of _M. floridensis_ in vegetable production fields is important for disease management throughout the state, since the host range is likely different from other _Meloidogyne_ spp.

Reference:
(1) ZA Handoo, et al. J Nematol 2004; 36: 20.

--
ProMED-mail
<promed@promedmail.org>

[A root-knot nematode species, previously unnamed and assumed to be "race 3" of _Meloidogyne incognita_, has now been classified as a new species, _M. floridensis_ (Mf). Mf 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. Scientists found the pest's penchant for
nematode-resistant rootstock characteristic, which stimulated further research. Morphological, cytological, molecular and host-range studies conclusively determined the taxonomic position of the nematode. Using
scanning electron microscopy, it was demonstrated that differences between Mf and _M. incognita_ were recognized. Mf did not exhibit the same host affinities as _M. incognita_. Mf reproduced abundantly on Nemaguard and Guardian peach rootstocks, whereby _M. incognita_ did not. Alternately, Mf does not reproduce in peppers as does _M. incognita_. Molecular studies confirm the uniqueness of Mf from _M. incognita_ and other root-knot nematodes.

Link: <http://plpnemweb.ucdavis.edu/nemaplex/Taxadata/G076S71.htm> - Mod.DH]