Molecular characterization of Meloidogyne incognita races based on DNA sequences of internal transcriber spacers of ribosomal DNA

The four Indian races of Meloidogyne incognita were characterized using internal transcriber spacers 1 and 2 of ribosomal DNA (rDNA). rDNA is amplified from the genomic DNA of the four races using polymerase chain reaction, cloned and sequenced. Amplification of rDNA from the four races resulted in about 800 base pair DNA fragment that included both ITS 1 and ITS 2, the 5.8 S rRNA gene and a small portion of the 3′ end of the 18S gene and the 5′ end of the 28 S gene. Alignment of ITS sequences of the four races indicated that there was variation in the sequence among the four races resulting in different restriction sites which can be used for differentiating the races. Phylogenetic analysis of the rDNA sequence data indicated that race 1 and race 4 were the most closely related forming one cluster to which race 2 was related. Race 3 was forming entirely a separate cluster.