First Report of Estonian Cyst Nematode Cactodera estonica from India

摘要

Among plant parasitic nematodes, cyst-forming nematodes (Heteroderidae) are the most notorious pathogens of agriculture and horticulture crops, and most species are restricted to cool climates (Baldwin and Mundo-Ocampo, 1991; Madani et al., 2004; Ma et al., 2008). In November 2016, a survey for identification and characterization of cyst nematodes was carried out in the Nilgiri hills, South India. During the survey, a large number of cysts were recovered from the rhizosphere and from the root system of Polygonum nepalense (Polygonaceae). Soil samples were subjected to Fenwick can method for cyst extraction, and the cysts were handpicked using a sterilized forceps under a stereo zoom microscope (Fenwick, 1940). The collected cysts were subjected to morphological and molecular characterization. The cysts were characterized by their dark brown color, lemon shape, as well as distinct neck and vulval cones. The vulval cone of the cyst was excised using the method described by Mulvey, 1972 and observed under a compound microscope. A comprehensive study of the vulval cone showed the typical circumfenestrate pattern. The cyst measurements (n = 5) were length 550.45 6 12 (470.72–687.64) mm, width 454.41 6 9 (391.51–541.88) mm, neck length 97.76 6 4.1 (93.85–102.77) mm, length-to-width ratio 1.4 6 0.16 (1.2–1.6) mm, and vulval cone length 47.44 6 3.9 (40.73–53.63)mm. The eggs recovered from these cysts were covered with small protuberances/tubercles. The second-stage juveniles were tapering posteriorly with a well-developed stylet and round basal knobs; tail tapering with a hyaline tail terminal. Second-stage juveniles (n = 15) showed the following morphometric characters: body length 469 6 15 (418–526) mm, a = 25.37 6 2.8 (21.23–28.4), b = 4.146 0.5 (0.4–4.8), b9 = 4.560.6(3.8–5.5),c=11.3361.1(9.54–12.16),c9=2.246 0.4(1.56–2.98),bodywidth18.7368(17.43–19.59) mm, stylet length 21.21 6 2.2 (19.6–23.16) mm, tail length 42.5 6 3.6 (34.8–45.57) mm, hyaline tail length 18.30 6 1.08 (16.2–19.6) mm, lip height 3.58 6 0.3 (3.4–4.1) mm, and lip width 8.83 6 0.9 (7.5–9.7) mm. The observations of cyst shape, eggs, vulval cone, and second-stage juveniles were typical of the genus Cactodera Krall Krall, 1978 (Golden and Mulvey, 1983). For further confirmation, the cysts were subjected to molecular analysis.