TABLE CONTENTS

SESSION TWENTY-SIX – MOLECULAR APPLICATIONS IN
DIAGNOSTICS AND NEW NEMATODE THREATS
CONVENORS: ANDREA SKANTAR & SERGEI SUBBOTIN
Progress and Challenges in the Molecular Identification of Plant-parasitic
Nematodes at the USDA ARS Nematology Laboratory
Skantar, A.M. (1), L.K. Carta (1), Z.A. Handoo (1), M.K. Nakhla (2), L. Levy (2) &
D.J. Chitwood (1)
(1) USDA-ARS Nematology Laboratory, Beltsville, Maryland; (2) USDA-APHIS-PPQ-CPHST, National Plant
Germplasm and Biotechnology Laboratory, Beltsville, Maryland
One mission of the USDA Agricultural Research Service Nematology Laboratory in
Beltsville, MD is to provide nematode identifications that are urgently required by ARS
scientists, federal and state researchers, and regulatory agencies for research, regulatory
actions, and control purposes. In addition to traditional morphology-based taxonomic
approaches, molecular methods are often required to confirm diagnoses or to provide
conclusive identification in those instances when species morphology is ambiguous or when
microscopic examination is impractical to perform. Here we will highlight current
approaches, challenges, and new developments in molecular identification of plant-parasitic
nematodes within the context of some recent diagnostic scenarios involving Globodera,
Meloidogyne, and Pratylenchus spp.
Specific Diagnostic and Genetic Variability of Meloidogyne mayaguensis
Isolates Revealed by Molecular Markers
Tigano, M. (1), P. Castagnone-Sereno (2), C.C. Teixeira (1), M.F.A. Santos (1),O. Randig (3)
& M.D.G.C. Carneiro (1)
(1) Embrapa Recursos Genéticos e Biotecnologia, C.P. 02372, 70849-970 Brasília, DF, Brazil; (2)INRA,
UMR1064 IPMSV, BP167, F-06903 Sophia Antipolis, France; (3) CNPq/COAGR, Ed. Nazir I, Bloco A, Sala
301, 70750-501 Brasília, DF, Brazil
Meloidogyne mayaguensis is an extremely polyphagous root-knot nematode. Disease caused
by this species is a matter of grave concern in Brazil where it is responsible of serious
economic damages on guava crops. Based on sequence analysis of a highly repetitive satellite
DNA family characterized in the genome of M. mayaguensis, primers were developed that
provide a specific and very sensitive PCR diagnostic methodology. In order to further analyze
the intraspecific genetic variability of the nematode, sixteen M. mayaguensis isolates from
different geographical regions and hosts were compared using a variety of biochemical and
molecular markers. All the isolates showed the same phenotype based on either isoesterase
electrophoresis or amplification of. ribosomal and mitochondrial DNA particular regions.
Further analysis with different neutral molecular markers (RAPD, ISSR and AFLP) showed a
high level of homogeneity among the isolates, and resulted in very similar clustering of the
isolates in the individual trees obtained with each marker. Although this root-knot nematode
displays a very wide host range and worldwide distribution, these molecular data confirm that
M. mayaguensis is genetically a very homogenous species, in agreement with its mitotic
parthenogenetic mode of reproduction.
5 th International Congress of Nematology, 2008 97