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First Report of the Cereal Cyst Nematode Heterodera filipjevi on Winter Wheat in Montana

Dyer, A. T., Al-Khafaji, R., Lane, T., Paulitz, T., Handoo, Z. A., Skantar, A. M., Chitwood, D. J.
Plant disease 2015 v.99 no.8 pp. 1188
ribosomal RNA, Heterodera avenae, body length, roots, juveniles, ribosomal DNA, internal transcribed spacers, hatching, planting, morphometry, polymerase chain reaction, neck, tail, stylets, winter wheat, eggs, cold, Heterodera latipons, species identification, spring, genetic databases, cysts (developmental stages), population, cyst nematodes, light, Russia, Tajikistan, United Kingdom, China, Oregon, Montana
Among the cereal cyst nematode complex, three species-Heterodera avenae, H. filipjevi and H. latipons-are the most destructive for wheat. Although H. avenae occurs in several U.S. states, H. filipjevi was discovered in the United States in Oregon in 2008 and has since been reported only in Washington. In Chouteau County, Montana, a winter wheat field reported to contain H. avenae was observed with localized areas of heavily stunted Yellowstone winter wheat. Roots from affected plants displayed moderate numbers of nematode cysts with no associated proliferation of lateral roots. Living nematode cysts from wheat roots from the affected field were examined morphologically and by PCR for species identification. Observations of morphological characters critical for identification indicated that the specimens were H. filipjevi. Diagnostic measurements of second-stage juveniles included length of body, stylet with anchor-shaped basal knobs, tail, and hyaline tail terminus. The lateral field had four lines; the inner two were more distinct. Shapes of the tail, tail terminus, and stylet knobs were also consistent with H. filipjevi. The lemon-shaped cysts were light brown to yellow and had a zigzag pattern and bifenestrate vulval cone; diagnostic morphometrics included body length excluding neck, body width, length/width, neck length and width, fenestra length and width, heavy underbridge, vulval slit, and many bullae. Molecular analysis of internal transcribed spacer (ITS1 and 2) and 28S rRNA confirmed identity as H. filipjevi. Amplicons generated from three J2 were cloned and sequenced. Sequences from the 28S region were >99.9% identical to those of H. filipjevi from China but distinct from several populations of H. avenae (99.0-99.2%). The ITS rDNA from this population matched with 99.9% identity several H. filipjevi sequences available from GenBank, including ones from Russia, Tajikistan, UK, USA, and China. The next closest species match was H. avenae, showing 96-97% identity to the Montana population. This is the first report of H. filipjevi from Montana. Importantly, eggs from H. filipjevi are noted for hatching in the fall during winter wheat planting and therefore may more greatly affect winter wheat than H. avenae, whose eggs hatch only in the spring after a cold period. Moreover, resistance in wheat against these two nematode species is different and will require additional considerations.