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First Report of Heterodera elachista on Zea mays and Echinochloa crusgalli var. mitis in Liaoning Province, China

Xiao, D. X., Feng, Y. X., Zhou, Y., Xuan, Y. H., Chen, L. J., Wang, Y. Y., Liu, X. Y., Duan, Y. X., Zhu, X. F.
Plant disease 2019 v.103 no.6 pp. 1433
DNA, Echinochloa crus-galli, Heterodera, Zea mays, aerial parts, body length, corn, crop production, cyst nematodes, females, financial economics, hosts, juveniles, new geographic records, parasitism, ribosomal RNA, rice, roots, soil, soil sampling, stylets, surveys, tail, China, Italy, Japan
During a survey for cyst nematode in May 2017, cyst nematodes were detected from a corn field that also contained barnyard grass (Echinochloa crusgalli var. mitis) in Anshan, Liaoning Province. Cysts and second-stage juveniles (J2) were isolated from soil samples. White females were observed on both roots of corn and barnyard grass in further field investigation, but aboveground parts had no obvious symptoms. Five 3-week-old corn plants cv. Zhengdan 958 and barnyard grass plants growing in pots filled with sterile soil were inoculated with 981.5 ± 106 J2s. Two corn and two barnyard grass plants were gently removed from the pots 30 days after inoculation, and females were observed on the roots of all hosts. After 3 months, a total of 33 and 41 cysts, respectively, were detected from soil by the sieving-decanting method for the other three corn and barnyard grass plants. Cyst nematodes obtained from soil and plant samples had uniform morphological and molecular characteristics and were confirmed to be Heterodera elachista. Cysts (n = 15) had the following characteristics: spherical to lemon shaped, vulval cone ambifenestrate, vulval bridge narrow, medium sized underbridge, with a few dark brown bullae, body length (not including the neck) ranging from 321.3 to 503.5 μm (mean = 421.7 μm, SD = 53.1); body width ranged from 256.2 to 399.9 μm (322.2, 44.8); fenestrate length of 27.2 to 41.2 μm (33.7, 6.0) and width of 25.7 to 38.8 μm (34.1, 5.9); underbridge length from 65.9 to 78.8 μm (72.8, 6.6); and vulval slit length from 31.6 to 46.0 μm (36.4, 8.3). J2s (n = 17) had the following characteristics: body length ranging from 338.7 to 445.1 μm (mean = 396.0 μm, SD = 31.7); stylet length from 17.7 to 20.8 μm (19.2, 0.7) with rounded knob; tail length of 51.8 to 66.8 μm (59.0, 4.2); and hyaline terminal tail ranged from 26.2 to 34.0 μm (30.5, 2.1); lateral field with three lines. There were no significant differences in measurements and morphological description between the population of H. elachista from Anshan and the Japanese population (Ohshima 1974). DNA was extracted from single J2s (Subbotin et al. 2008), and the rDNA-internal transcribed spacer (ITS) and D2/D3 fragments of the 28S RNA were amplified with universal primers TW81 and AB28, and D2A and D3B, respectively. The ITS sequence (MH712504) and 28s sequence (MH767024) were submitted to GenBank. The ITS sequence was remarkably similar to the H. elachista isolate from Italy with 99.5% similarity (KC618468 and KC618469) and exhibited 99.8% similarity with the isolate from Ningxia Province, China (HM560778). H. elachista was first discovered on rice in Japan (Ohshima 1974). In 2012, it was reported on rice in China by Ding et al. (2012). H. elachista was first reported to parasitize corn resulting in economic losses in Italy in 2013 (De Luca et al. 2013). As far as we know, this is the first report of H. elachista on E. crusgalli var. mitis and corn in China. Though this nematode was detected from only around 13 ha of corn fields in Anshan, it is still a potential threat to corn production in the northeast of China.