The potato cyst nematodes (PCN) Globodera rostochiensis (Wollenweber) Skarbilovich, 1959 is considered the most damaging nematode pest of potato worldwide that causes significant yield losses, and this nematode is recognized and listed as a quarantine nematode in many countries (EPPO 2017). China is currently the largest producer of potato in the world, while the total production is also the highest (Guan and Cai 2019). The survey for cyst nematodes on potato were conducted in Yunnan and Sichuan provinces of China during 2018–2020, numerous cysts were observed on potato roots in Huize County and Ludian County of Yunnan Province, Zhaojue County and Yuexi County of Sichuan Province. Cysts and second-stage juveniles (J2s) were isolated from each soil sample using the Cobb decanting and sieving method. The morphology of cysts and J2s and molecular analysis established the identity of this species as golden cyst nematode Globodera rostochiensis (Subbotin et al. 2010). For morphological analysis, the cysts were characterized by smoothly rounded with a small projecting neck, brown and golden color, terminal cone was absent and circumfenestrate. The key morphometrics of cysts (n=25) were: length excluding neck 705±24 (689–747) μm, width 698±28 (678–759) μm, number of cuticular ridges between anus and vulval fenestra 17.3±1.7 (14–19); fenestral diameter 13.6±1.1 (12.25–15.45) μm; distance from anus to the edge of fenestra 63.7±11.3 (48.23–79.14) μm; Granek’s ratio 4.7±0.7 (3.92–5.75). The key morphometrics of J2s (n=25): body length 453.9±16.6 (440–496) μm, stylet length 21.9±1.0 (20.3–24.3) μm, tail length 51.1±3.2 (45.5–55.5) μm, and hyaline region length 24.4±2.5 (21.7–29.9) μm. Morphology of the cysts and J2 were consistent with those of G. rostochiensis (Subbotin et al. 2010; EPPO 2017). Moreover, the identification result was confirmed by PCR using universal primers TW81 (5´-GTTTCCGTAGGTGAACCTGC-3´) and AB28 (5´-ATATGCTTAAGTTCAGCGGGT-3´) for ITS region and D2A (5´-TTTTTTGGGCATCCTGAGGTTTAT-3´) D3B (5´-AGCACCTAAACTTAAAACATAATGAAAATG-3´) for rDNA-28S region, respectively. The ITS rDNA sequences (GenBank accessions MZ042365, MZ042366, MZ042369, and MZ042370) exhibited 99.83% identity match to G. rostochiensis sequences available in the GenBank (GQ294513). Sequence from the 28S region (GenBank accessions MZ057595, MZ057596, MZ057599, and MZ057600) was 99.33% similar to those of G. rostochiensis isolate from MF773722. The species was also confirmed with species-specific primers ITS5 (5´-GGAAGTAAAAGTCGTAACAAGG-3´) and PITSr3 (5´-AGCGCAGACATGCCGCAA-3´) (Bulman and Marshall 1997), a single 434-bp fragment was obtained from Huize, Ludian, Zhaojue and Yuexi populations. The pathog enicity testing of Huize, Ludian, Zhaojue and Yuexi, three weeks-old potato plants (cv. Qinshu 9)
were inoculated with 2 000 eggs, and cultured in an incubator at 23°C/20°C with a 16 h/8 h light/dark photoperiod. After three months inoculation, 36±7.2 cysts and females were extracted from the infested potato roots, no females and cysts were observed on control plants.
This is the first report of potato golden cyst nematode G. rostochiensis in China.
