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Restriction fragments from purified mitochondrial DNA can be readily detected following rapid end-labeling with [α-32P] nucleoside triphosphates and separation by gel electropboresis. Mitochondrial DNA from 12 populations of Meloidogyne species was digested with 12 restriction enzymes producing more than 60 restriction fragments for each species. The mitochondrial genome of M. arenaria is the most genetically distinct of the four species compared. M. arenaria shows approximately 2.1-3.1% nucleotide sequence divergence from the mitochondrial genomes of M. javanica, M. incognita, and M. hapla. Among the latter three species, interspecific estimates of sequence divergence range from 0.7 to 2.3%. Relatively high intraspecific variation in mitochondrial restriction fragment patterns was observed in M. hapla. Intraspecific variation in M. incognita resulted in sequence divergence estimates of 0.5-1.0%. Such polymorphisms can serve as genetic markers for discerning mitochondrial DNA genotypes in nematode populations in the same way that allozymes have been used to discern nuclear DNA genotypes.