First Report of the Stubby Root Nematode, Paratrichodorus minor, in Mainland China

Abstract

The stubby root nematode, Paratrichodorus minor (Colbran, 1956) Siddiqi, 1974, is an economically important species. It not only causes direct damage to the meristemic tissues of plants, but also can be a vector of Tobacco rattle virus and Pepper ringspot virus (2). It has been documented in Afghanistan, Argentina, Australia, Brazil, Canary Islands, Cuba, Egypt, Fiji, India, Israel, Ivory Coast, Japan, Java, Mauritania, New Zealand, Nicaragua, Philippines, Puerto Rico, Senegal, South Africa, Taiwan, Upper Volta, the United States, the former USSR, and Venezuela (1). During a recent investigation on Trichodoridae occurring in China, eight stubby root nematode populations were detected in Hainan, Yunnan, and Fujian provinces in the rhizospheres of eggplant (Solanum melongena), Chinaberry (Melia azedarach), lettuce (Lactuca sativa), longan (Dimocarpus longan), peach (Prunus persica), pear (Pyrus sp.), and walnut (Juglans regia) in soils ranging from clay to sand. The eight populations had similar morphological and molecular characters. The females were cigar shaped with rod-shaped vaginal sclerotization parallel to the longitudinal body axis with a quadrangular vagina in side view having a short vulval slit. The key morphometrics of females were consistent with those of P. minor: body length, 631 to 757 μm; body diameter, 27 to 43 μm; onchiostyle, 35 to 36 μm; a, 18 to 24; b, 4.9 to 5.5; v%, 53 to 55; length of vagina, 10.8 to 11.1 μm; and size of vaginal pieces, 1.7 to 1.9 μm. Males in P. minor are rare and were not found in any of the eight populations. Partial sequences of the 18s RNA gene of each population were amplified with forward primer 5′-AAA GAT TAA GCC ATG CAT G-3′ (2), and reverse primer 5′-AGT CAA ATT AAG CCG CAG-3′ (3), which yielded a PCR fragment of 1,153 bp. PCR products from all eight populations were sequenced and submitted to GenBank and assigned Accession Nos. GQ995703, GQ995704, GQ995705, GQ995706, GQ995707, GQ995708, GQ995709, and GQ995710. The sequences exhibited 99.8 to 100% similarity with those of P. minor isolates DQ345526, AM269897, AJ438052, AJ438053, and AJ438058 from GenBank. Morphological and molecular identification confirmed that all populations were P. minor. To our knowledge, this is the first report of P. minor in mainland China. References: (1) K. Boutsika et al. Nematology 6:145, 2004. (2) W. Decramer. The Family Trichodiridae: Stubby Root and Virus Vector Nematodes. Kluwer Academic Publishers, Dordrecht, the Netherlands, 1995. (3) I. S. Waite et al. Soil Biol. Biochem. 35:1165, 2003.