First Report of Cereal Cyst Nematode (Heterodera filipjevi) on Winter Wheat in Xinjiang Uygur Autonomous Region, China

Abstract

The cereal cyst nematode Heterodera filipjevi is considered to be one of the most important plant parasitic nematodes attacking most cereals and can cause significant crop losses (Sikora 1988). In China, this nematode was first recorded in Henan province in 2009 and a few years later in Anhui province (Peng et al. 2016). During May 2015 to August 2016, a survey for important plant parasitic nematodes on wheat and sugar beet was undertaken in Xinjiang Uygur Autonomous Region of China; 50 soil samples were collected, and the weight of each sample was about 1 kg. The cysts and second-stage juveniles (J2) were extracted from each soil sample using the sieving-decanting method. Morphological and molecular studies (Subbotin et al. 2010) of cysts and J2 confirmed the identification of H. filipjevi in two wheat-field soil samples from Xinyuan county of Yining city. There were no significant above-ground symptoms on wheat, but a few females were found on roots. The cysts were lemon shaped with light to dark brown cyst walls. Subcrystalline layer thick, valval core ambifenestrate, bullae large and numerous, and underbridge observed. The key morphometrics of cysts (n = 10) were length excluding neck (range = 705 to 887 μm, mean = 775 µm, standard deviation = 30.5); width (478 to 694, 571, 15), fenestra length (45.2 to 63.9, 54.7, 2.1), fenestra width (26.9 to 34.8, 28.4, 1.2), length of vulval slit (7.5 to 12.5, 9.4, 0.5), and length of underbridge (71.4 to 84.5, 76.4, 4.8). Measurements of J2s (n = 20) included length of body (range = 481.1 to 581.5 μm, mean = 540 µm, standard deviation = 7.1), stylet (24.5 to 27, 24.7, 0.2), tail (53.4 to 65.3, 61.2, 1.4), and hyaline tail terminus (30.4 to 42.2, 36.5, 0.7). Genomic DNA was isolated from single cysts (n = 5), and the internal transcribed spacer regions were amplified with primers TW81 (5′-GTTTCCGTAGGTGAACCTGC-3′) and AB28 (5′-ATATGCTTAAGTTCAGCGGGT-3′) (De Ley et al. 1999). The obtained sequences (GenBank accession nos. KY448472 and KY448473, 1,054 bp) were found to be 99 to 100% identical to those of H. filipjevi from the United States (KP878490.1 and GU079654.1), Turkey (KR704304.1 and KR704308.1), and China (KT314234.1 and GU083595.1). The species-specific primers were used and produced a single band specific for H. filipjevi (Peng et al. 2013). Pathogenicity of the H. filipjevi was confirmed by infection of wheat and examination of the nematode development and reproduction. Wheat (Triticum aestivum ‘Wenmai 19’), was cultured in 300 cm³ pots filled with autoclaved soil in a glasshouse, and 800 eggs were inoculated into the soil near the roots of 4-day-old seedlings. The parasitic J2s, third and fourth-stage juveniles, and adult females were observed in roots stained with acid fuchsin at 7, 14, 28, and 35 days after inoculation (DAI), and an average of 51 cysts per pot were extracted 50 DAI. The new cysts’ morphological and molecular characteristics were identical to the H. filipjevi cysts from the original soil samples. To our knowledge, this is the first report of H. filipjevi in Xinjiang Uygur Autonomous Region, China. If this nematode continues to spread in China, it could become be a new threat to cereal production, so some effective control should be taken to prevent further spread.