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The rice root-knot nematode, Meloidogyne graminicola is an important pathogen, impacting rice, wheat and possibly vegetable production in South-East Asia. Ten isolates of M. graminicola from broad geographic areas were compared using traditional and molecular methods. Total body length, oesophageal length, maximum body width and tail length were measured in 40 juveniles and the perineal patterns of 10 females per isolate were compared. Pathogenicity was determined on a variety of hosts. The internally transcribed spacer (ITS) region was amplified and sequenced to confirm the identity and phylogenetic relationships of the isolates. Substantial variation observed in morphometric measurements among and within isolates did not correlate with the geographic source of the isolates. All the isolates were similar in host range, but the M. graminicola-Florida isolate differed from the other nine isolates in that it was not pathogenic to rice cvv. Labelle, LA 110, Cocodrie, BR 11 or Mansuli, suggesting that M. graminicola consists of more than one race. ITS sequences of all 10 isolates matched with those of M. graminicola in GenBank and formed a single clade in the phylogenetic analysis with minor variations among and within isolates. Multiple ITS sequences occurred within individual juveniles in some of the isolates. |
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