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Rice (Oryza sativa L.) is one of world's most widely consumed staple foods and plays an important role in the diet of more than half of the world's population.Rice production is limited by several abiotic and biotic factors.Among biotic factors, plant-parasitic nematodes are considered as important harmful pathogens which can cause either direct or indirect damage to their host.Rice root nematodes (RRN) belonging to the genus Hirschmanniella are one of the most serious pests and commonly found in majority of rice growing regions.All nematodes of Hirschmanniella spp.are migratory endoparasite of roots and every life stages of this nematode (except egg stage) can invade rice roots.The genus Hirschmanniella includes about 35 species and more than half of them are found on rice paddy fields.In China, a total of seventeen species of Hirschmanniella associated with rice have been reported.Identification of Hirschmanniella species by means of morphology,morphometric and molecular was carried out in this study.We observed two species,Hirschmanniella oryzae and Hirschmanniella mucronata, from the collected rice root and soil samples.Analysis of the ITS-rDNA Sequence showed that high intraspecific variation among the nucleotide sequence of ITS regions of tested Hirschmanniella isolates (sequence homology 88%~99%to H.oryzae and 99% to H.mucronata).The morphology and morphometric characterization of H.mucronata was largely similar to the original description of type specimens, but slightly differed by having wider maximum body diameter.In H.oryzae, comparison with the reported data indicated that the nematode in the present measurements have wider body width, higher'a'value,longer pharyngeal glands and median bulb distance from anterior end, tail terminus with subterminal notch.These two species can be easily separated by their stylet length and body length.For detection and identification of H.oryzae, sixty random 10-mer primers were used in RAPD assay.One of them gave reproducible amplification patterns and developed into sequence-characterized amplified region (SCAR) marker specific for target species, H.oryzae.The expected fragment size of 475 bp was observed in all H.oryzae isolates but not in other species.In conclusion, the combination of morphology and molecular identification of rice root nematodes will be more accurate way to avoid misinterpretation of the species and overestimation of genetic diversity.Better understanding and rapid diagnosis of this economically important pest of rice roots will help in selection of proper management.