Morphological and molecular characterizations of Heterodera oryzae in Korea

Rice is one of the most important staple grains in Korea and the largest starch source in addition to its usefulness in the production of beverages. Under different areas and environments of production, various pests and diseases including soil-borne plant pathogens such as plant-parasitic nematodes can compromise rice productivity. In a survey to identify plant parasitic nematodes on rice, cyst nematodes were encountered in rice fields that required characterization and identification. Phylogenetic analysis of the LSU D2-D3 region and ITS region could not separate the studied species from Heterodera elachista. However, phylogenetic analysis of the COI gene of the mitochondrial DNA clearly separated H. elachista from the new species into two different clusters. Combining morphology and molecular diagnostics, the species was identified as Heterodera oryzae belonging to the 'Cyperi' group whose cysts are characterized by vulval cones that are ambifenestrate, underbridge present with bullae. Second-stage juveniles have three incisors in the lateral field with long tails and long hyaline region.