A species-specific satellite DNA family in the genome of the coffee root-knot nematode Meloidogyne exigua: application to molecular diagnostics of the parasite.
SUMMARY A new BglII satellite DNA has been isolated, cloned and sequenced from the coffee root-knot nematode, Meloidogyne exigua (Nematoda: Tylenchida). It is represented as tandemly repeated sequences with a monomeric unit of 277 bp. The monomers are present at approximately 17 900 copies per haploid genome, and represent about 9.7% of the total genomic DNA. Twenty randomly chosen monomers have been sequenced. The deduced unambiguous consensus sequence is 277 bp long, and displays an A + T content of 54.2%. The monomers are very homogenous in sequence, showing on average 2.4% divergence from their consensus. Therefore, it is hypothesized that this repeated family may have recently appeared in the genome of the nematode, through some extensive amplification burst. Using a cloned monomer as a probe, dot-blot experiments demonstrated the species-specific distribution of the BglII satellite DNA. Moreover, squash-blot assays allowed us to detect single M. exigua individuals, at any developmental stage, and even within root tissues, without the need for preliminary DNA purification. From these results, it is concluded that the procedure described, using the satellite DNA as a sensitive species-specific probe, should constitute an improved and accurate diagnosis method for the detection and identification of the nematode, which would contribute to the implementation of targeted pest management strategies in all coffee growing countries of South and Central America.
Randig
Onivaldo
O
INRA, Unité Interactions Plantes-Microorganismes et Santé Végétale, BP2078, 06606 Antibes Cedex, France.
Bongiovanni
Michel
M
Carneiro
Regina M D G
RM
Sarah
Jean-Louis
JL
Castagnone-Sereno
Philippe
P