First Record of Steinernema Glaseri Steiner, 1929 (Nematoda: Steinernematidae) in Asia, with Notes on In- Traspecific Variation
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SHORT COMMUNICATION S. P. STOCK1), H. Y. CHOO2) & H. K. KAYA1): First record of Steinernema glaseri Steiner, 1929 (Nematoda: Steinernematidae) in Asia, with notes on in- traspecific variation. Nematodes of the family Steinemematidae are obligate parasites of insects and in recent years have become important agents for biological control (Gau- gler & Kaya, 1990). Among the steinemematids, Steinernema carpocapsae Weiser, 1955 and Steinernema feltiae Filipjev, 1934 appear to have a global distribution. They have been reported from Europe (Ehlers et al., 1991), North America (Poinar, 1990), South America (De Doucet, 1995; Stock, 1995), Aus- tralia (Poinar, 1990) and Asia (Choo et al., 1995; Mamiya, 1996). In contrast, S. glaseri Steiner, 1929 appears to have a more restricted distribution with reports only from eastern USA, Argentina, Brazil and Spain (Poinar, 1978; Pizano et al., 1985; De Doucet, 1990; De Doucet and Gabarra, 1994). However, this dis- tribution information should be taken as partial since the identification of many steinemematids collected from different parts of the world has been at the generic level and not at the species level (Hominick et al., 1996). In a survey conducted in South Korea during the summers of 1990 and 1991, nine isolates of steinemematids were collected (Choo et al., 1995). In that study, only three isolates, Pocheon 1, 2 and 3 (Gyeonggi Province), recovered from forest areas, were identified as S. carpocapsae. Stock et al. (in press) identified two other isolates (Sancheong I and II), collected in mountain forest areas, as a new Steinernema species. The remaining isolates (Mungyeong, Dongrae, Nam- cheju and Hanrim) were only identified as Steinernema spp., with characteristics of S. intermedia Poinar, 1985 and S. glaseri. We report herein the identification and morphological characteristics of two of these isolates, Mungyeong and Don- grae. Unfortunately, isolates Namcheju and Hanrim were lost and were unable to provide further information. 1) Department of Nematology, University of California Davis, Davis CA 95616, USA. 2) Department of Agricultural Biology, Gyeongsang National University, Chinju, Gyeongnam, 660-701, Republic of Korea. 378 Both Mungyeong and Dongrae isolates were recovered from soil in the SE of Korea (Gyeongbuk Province). The Mungyeong isolate was collected from common lamb-quarters and the Dongrae isolate was recovered from a golf course in the city of Pusan. The soil texture of the samples collected was classified as sandy clay and sandy for the Mungyeong and the Dongrae isolates, respectively (Choo et al., 1995). Isolates were obtained by baiting soil samples with last instar larvae of the greater wax moth, Galleria mellonella (L.) (Bedding, 1975). Insect cadavers were dissected 3-4 days and 5-6 days after infection to obtain first and second generation adults. Infective juveniles were recovered during the first two days of emergence. For morphological and morphometric studies, the nematodes were examined either live or heat-killed and relaxed in Ringer's solution. Nematodes were fixed in TAF (triethanolamine formalin) and processed to glycerin (Kaya & Stock, 1997). Measurements were made using a Leitz Ortholux II microscope with an ocular micrometer and through a video digitizer using JandelTM software. Isolates Dongrae and Mungyeong were cross-bred with each other and with the NC isolate of S. glaseri and with S. anomali Kozodoi, 1984. Thirty infective juveniles of each isolate/species were surface sterilized in 1 % Hyamine solution (methylbenzethonium chloride) and placed in hanging-drops of G. mellonella haemolymph diluted with 10 pl of serum-free insect tissue culture solution (SF 900 II SFM Gibco@) (Kaya & Stock, 1997). Hanging-drop slides were placed individually in Petri dishes (9 cm diameter) containing a single piece of filter paper saturated with distilled water. The dishes were wrapped with parafilm and incubated at 25°C in the dark until preadults formed. A preadult of each Korean isolate was then placed in hanging-drop dishes with a preadult of the opposite sex of either of the test species (S. glaseri and S. anomali) for 10 days. Each cross-mating was conducted over a period of 5 days and replicated 15 times. Control matings contained individually selected males and females of the same isolate/species. In general, isolates Dongrae and Mungyeong are morphologically similar to each other. The morphology of these isolates agrees essentially with the original description of S. glaseri, provided by Steiner (1929) and with the description of the NC isolate (Poinar, 1978). The diagnostic characters of this species include the rounded tail in the males and the first generation females, the notch in the tip of the spicules, and the size of the infective juveniles. However, when compared with each other and with the NC isolate, some patterns of morphological variation were observed within the first generation adults. The first generation female of the Dongrae isolate usually has a more protruded vulva (Fig. lA). In contrast, the vulva of the female of the Mungyeong .