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First Report of the Southern Root-Knot Nematode Meloidogyne incognita on the Invasive Weed Araujia sericifera in Italy

Moth plant, Araujia sericifera, is native to South America and was exported to many other countries as an ornamental plant. However, it is now considered an invasive, perennial, noxious weed in Italy. Because of the ability of this plant to spread rapidly and invade natural ecosystems, A. sericifera has been included on the Alert list by the European and Mediterranean Plant Protection Organization (EPPO). In September 2013, numerous plants of A. sericifera with chlorotic leaves and large root-galls were observed in agricultural fields, gardens, and uncultivated locations in Nocera Inferiore, Salerno Province, Italy. Ten samples were collected from a vegetable farm (40°45′40.8″ N, 14°38′18.4″ E) and nematodes were extracted from soil and root samples using standard procedures (1). Meloidogyne sp. was found in all soil and root samples, with nematode population densities ranging from 420 to 1,270 eggs and J2s/10 cm³ of soil and 84 to 2,200 eggs and J2s/5 g of fresh roots. The morphological identification of the nematode was based on characterization of second-stage juveniles (J2s), males, eggs, and females (2). Measurements of J2s (n = 30) include: mean body length (L) = 403 ± 3.7 μm; L/maximum body width = 27.5 ± 0.3; L/esophageal length = 6.2 ± 0.1; stylet length = 12.8 ± 0.1 μm; L/tail length = 9.5 ± 0.1; tail length = 42.5 ± 0.3 μm. Males (n = 10): L = 1,491 ± 0.04 μm; L/maximum body width = 44.4 ± 0.8; L/esophageal length = 16.1 ± 0.3; stylet length = 22.1 ± 0.7 μm; spicules length = 30.1 ± 0.8 μm. Eggs (n = 30): length = 96.6 ± 1 μm; width = 45.1 ± 0.5 μm; length/width ratio = 2.1. Females (n = 20): L = 909.5 ± 38.4 μm; body width = 588.3 ± 19.3 μm; stylet length = 17.0 ± 0.2 μm. Perineal patterns of females had a high dorsal arch with wavy striae bending toward the lateral lines and the absence of distinct lateral line incisures. All measurements conformed to the description of Meloidogyne incognita (Kofoid & White, 1919) Chitwood 1949. DNA was extracted from five individual adult females from each sample and morphological identification was confirmed by a sequence-characterized amplified region (SCAR)-PCR technique using species-specific primers. The amplified product obtained was 1.2 kb in length, demonstrating proper amplification of the species-specific, length variant SCAR marker (3). Weeds are known to serve as hosts for nematodes in the absence of crop plants and to affect the success of nematode management programs. Meloidogyne spp. have been reported to survive and even thrive on weeds; among them, M. incognita is considered the most economically important agricultural nematode pest worldwide as it causes severe yield losses on many hosts. Thus, the invasive plant A. sericifera can be a potential reservoir for M. incognita in Italy and elsewhere. To our knowledge, this is the first report of M. incognita parasitizing A. sericifera.

References: (1) K. R. Barker. Page 19 in: An Advanced Treatise on Meloidogyne. Vol. II, Methodology. K. R. Barker et al., eds. North Carolina State University Graphics, Raleigh, 1985. (2) J. D. Eisenback et al. A Guide to the Four Most Common Species of Root-Knot Nematodes (Meloidogyne spp.), with a Pictorial Key. North Carolina State University, Raleigh, 1981. (3) C. Zijlstra et al. Nematology 2:847, 2000.