Molecular Diagnosis And Genetic Variability of New Isolates of Root – Knot Nematodes Meloidogyne Spp.on Cucumber Plants

Abstract

Results of the amplified DNA products of the ITS revealed the presence of two bands among the six amplified products,in position at about 500 bp as illustrated by agarose gel electrophoresis,then sequencing of the amplification products showed the presence of two species out of a total of six nematode isolates including Meloidogyne incognita and M. javanica which displayed some nucleotide differences through comparing the DNA sequence alignment of  their ITS and emphasized by a DNA Dot  plot for each species against the other,where a genetic similarity was 98.84%. Phylogenetic tree analysis for M.incognita showed that the closest species to it is M.incognita isolate CN 36 from China with 99.55% genetic similarity whilst more nucleotide differences were observed by two isolates (A-1and B-2) of M.incognita from Iraq with a genetic similarity of 97.99%%. As for M.javanica,the closest species to it is a group of three nematode species including: M.javaniac voucher M J- 21, M.incognita  isolate Nem Mi TG2 and Meloidogyne sp.Mj – c3b from  Brazil, India and New Zealand  respectively, after which nucleotide differences increased more,as it reached its maximum level with M. incognita isolate C N 36 with a  genetic similarity of 98.84%