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First Report of Root-Knot Nematode Meloidogyne arenaria on Atractylodis macrocephalae in China

Atractylodis macrocephalae is an important Chinese herbal medicine plant and its rhizome is of high medicinal value. In recent years, a severe decline in yield has been observed in Bozhou City (China's largest A. macrocephalae producing area), Anhui Province, China. A survey for plant-parasitic nematodes was conducted in this area from June to September 2011. Stunted plants displayed chlorotic or necrotic lower leaves near the ground part by the growth reduction; examination of the roots of stunted plants revealed the presence of galls typical of infestation by root knot nematode. Root nodules were found on the tap and lateral roots caused the fleshy tap root deformity. The incidence of diseased plants was estimated to be 45%, and yield loss was quantified as 43.5%. Nematodes were extracted from the root samples as previously described (4) and identified by morphology, enzyme analysis, and molecular characterization. Morphology of the female perineal patterns and measurements of the second-stage juveniles (J2s) matched those of the original description of Meloidogyne arenaria. Enzyme analysis of the esterase (Est) phenotype was also typical of the AII phenotype in M. arenaria (2). DNA was extracted according to a modified protocol (1), and the rDNA-internal transcribed spacer (ITS1_5.8S_ITS2) region was amplified with universal primers V5367 (5′-TTGATTACGTCCCTGCCCTTT-3′) and 26S (5′-TTTCACTCGCCGTTACTAAGG-3′). PCR yielded a fragment of 764 bp and the purified product was sequenced by Sanger's dideoxy chain termination method (ABI3730). Sequences were identical to that of M. arenaria in GenBank (Accession No. AF387092) (3). Amplification of the D2/D3 fragments of the 28S RNA with universal primers D2A (5′-ACAAGTACCGTGAGGGAAAGTTG-3′) and D3B (5′-TCGGAAGGAACCAGCTACTA-3′) yielded a PCR fragment of 758 bp. These sequences were also identical to that of M. arenaria in GenBank (Accession No. AF435803). For further confirmation, amplification of the IGS region with universal primers 5S (5′-TTAACTTGCCAGATCGGACG-3′) and 18S (5′-TCTAATGAGGGAACCAGCTACTA-3′) yielded a PCR fragment of 713 bp. These sequences were 99.64% homologous to that of M. arenaria (GenBank Accession No. MAU42342). To our knowledge, this is the first report of M. arenaria species on A. macrocephalae in China. The fleshy tap root of A. macrocephalae is the main edible part of the plant, and the damage caused by root knot nematode will potentially reduce the yield and quality of this herb.

References: (1) J. L. Cenis et al. Phytopathology 83:76, 1993. (2) P. R. Esbenshade and A. C. Triantaphyllou. J. Nematol. 17:6, 1985. (3) T. C. Vrain et al. Appl Nematol. 15:563, 1992. (4) L. F. Wang et al. Forest Res. 14:484, 2001.