First Report of the Cyst Nematode (Heterodera filipjevi) on Wheat in Henan Province, China.

ABSTRACT

During a survey for cereal cyst nematodes from May to June of 2009, cyst nematodes were detected in four wheat-growing areas (Liying, Xuchang, Weihui, and Yanjing) of Henan Province, China. The main wheat cultivar affected was Wenmai No.4. Almost 5.3 million ha of winter wheat are grown in Henan Province and 73% of the fields surveyed were found to be infested with Heterodera avenae (2). The affected wheat fields had stunted patches. Stunted seedlings had chlorotic or necrotic lower leaves, few or no tillers, and bushy, light brown roots leading to typical witches'-broom symptoms resulting from increased rootlet emergence at the nematode invasion sites. Individual roots had a knotted appearance. Cyst nematodes obtained from soil samples and plant samples at these four locations differed from those of H. avenae and had uniform morphological and molecular characteristics. Cysts were lemon shaped and bifenestrate, with an underbridge and strongly developed bullae. The lateral field of second-stage juveniles (J2) consisted of four incisures. These characteristics indicated that the four populations were H. filipjevi, a member of the 'H. avenae Group' of cereal cyst nematodes (1). Key morphological features were determined for cysts and J2. Cysts (n = 15) had the following characteristics, in addition to those described above light brown color; bifenestrate vulval cone with horseshoe-shaped fenestrate; body length (not including the neck) ranged from 690 to 790 µm (mean of 750 µm); body width ranged from 410 to 640 µm (mean of 540 µm); neck length ranged from 86 to 100 µm (mean of 96 µm); fenestrate length of 59 to 70 µm (mean of 67.7 µm) and width of 31.3 to 36.7 µm (mean of 35.2 µm); underbridge length from 59 to 71 µm (mean of 68 µm); and vulval slit from 6.9 to 8.6 µm (mean of 7.9 µm). J2 (n = 10) had the following characteristics body length ranged from 540 to 580 µm (mean of 550 µm); stylet length from 22.5 to 24.5 µm (mean of 23.5 µm) with anchor-shaped basal knobs; tail length of 52.5 to 62.5 µm (mean of 57.7 µm); and hyaline terminal tail ranged from 32 to 39 µm (mean of 33.8 µm). The tail had a sharp terminus. Amplification of the rDNA-internal transcribed spacer (ITS) region with primers TW81 and AB28 yielded a PCR fragment of 1,054 bp (3). Amplification of the D2/D3 fragments of the 28S RNA with universal primers D2A (5'-ACA AGT ACC GTG AGG GAA AGT TG-3') and D3B (5'-TCG GAA GGA ACC AGC TAC TA-3') yielded a PCR fragment of 782 bp. Digestion patterns of the ITS PCR fragments with AluI, CfoI, HifI, SatI, PstI, RsaI, TaqI, and Tru9I showed restriction profiles identical to that of H. filipjevi (3,4). Four ITS sequences (GU083595, GU083596, HM147944, and HM147945) and four D2D3 sequences (GU083592, GU083593, GU083594, and GU083597) from nematode samples collected in Liying, Xuchang, Weihui, and Yanjing, respectively, were submitted to GenBank. These sequences exhibited 99.4% similarity with that of H. filipjevi isolates from Germany (AY148400), Italy (AY347922), Russia (AY148401), Spain (AY148399), Tadzhikistan (AY148402), Turkey (AY148398 and AY148397), the United Kingdom (AY148403 and AF274399), and the United States (GU079654). To our knowledge, this is the first report of H. filipjevi in China. References (1) Z. A. Handoo. J. Nematol. 34250. 2002. (2) D. L. Peng et al. Proc. 1st Workshop Internat. Cereal Cyst Nemat. Initiative, Antalya Turkey, p. 29, 2009. (3) S. A. Subbotin et al. Nematology 1195, 1999. (4) G. Yan and R. W. Smiley. Phytopathology 100216, 2010.