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ISSN : 1225-0171(Print)
ISSN : 2287-545X(Online)
Korean Journal of Applied Entomology Vol.53 No.1 pp.51-57
DOI : https://doi.org/10.5656/KSAE.2013.10.1.083

Identification of Root-lesion Nematode (Pratylenchidae: Pratylenchus) Intercepted on Imported Plants

Dongwoo Kim, Jae-Yong Chun*
Plant Quarantine Technology Center, Animal and Plant Quarantine Agency, Suwon 443-400, Korea
Corresponding author:dollmock@korea.kr
December 18, 2012 October 30, 2013 November 22, 2013

Abstract

We identified the five root-lesion nematode species, Pratylenchus crenatus, P. fallax, P. kumamotoensis, P. panamaensis and P. penetrans from intercepted in quarantine inspection over the past five years. Their diagnostic characters are including number of lip annuli, stylet length, shape of the labial region, presence or absence of males, structure of lateral fields, shape of spermatheca, length of the post-vulval uterine sac and shape of tail and so forth. We described the photos, measurements and morphological characters.

Tylenchida , Pratylenchidae , Pratylenchus , Root-lesion nematode , Plant quarantine

수입식물에서 검출된 뿌리썩이선충(뿌리썩이선충과: 뿌리썩이선충속)의 진단

김 동우, 전 재용*
농림축산검역검사본부 식물검역기술개발센터

초록

최근 5년 동안 식물검역 현장에서 검출된 뿌리썩이선충속 선충을 분류하여 Pratylenchus crenatus, P. fallax, P. kumamotoensis, P. panamaensis, P. penetrans로 동정하였다. 이 종들의 진단형질은 구순부의 주름 수, 두부의 형태, 구침의 길이, 수컷의 유무, 측대의 구조, 수정낭의 형태, 후부자궁낭의 길이, 미부의 형태 등을 포함한다. 이들의 사진과 측정치 및 형태적 특징을 기술하였다.

Tylenchida , Pratylenchidae , Pratylenchus , 뿌리썩이선충 , 식물검역

    As the international trade increases, invasion of new pests are increasing (Kiritani, 2001). Invasive species can adopt, spread quickly because they don’t have any natural enemies in the new environment (Howard, 2004). In order to prevent the invasion of these pests, it needs the thorough inspection, collection of the information on pests and rapid identification of detected exotic pests (Rugman-Jones, 2006).

    Root-lesion nematode, the species belonging to the genus Pratylenchus Filipjev, 1936, is frequently detected in plant quarantine. There are more than 70 species around the world (Siddiqi, 2000; Palomares-Rius et al., 2010), 14 species were recorded in the Republic of Korea (Park, 1996; Park et al., 2002; Choi et al., 2006; Kim et al., 2006; Park et al., 2009). Only four species, P. brachyurs, P. crenatus, P. fallax, and P. zeae are listed as the regulated pest in announcement of Animal and Plant Quarantine Agency (No. 2013-137). These nematodes are migratory parasite that invade cortex of root, tubers, and other below-ground organs (Bridge and Starr, 2007). Their feeding activities results in destruction of host cell with formation of necrotic lesion (Baxter and Blake, 1968; Corbett, 1972; Acosta and Malek, 1981). It causes reduction of yields (Lownsberry, 1956; McKenry, 1989) or lowering of the market value of crops (Bernard and Laughlin, 1976). Their host range is wide, various crops are affected by root-lesion nematode worldwide (Vanstone et al., 1995; Kimpinski et al., 1989; Vanstone et al. 1998). In Korea, they cause the wilt disease in Chrysanthemum with soil pathogens (Lee et al., 2008), it affects export of Chrysanthemum. Also they were detected on several crops such as Perilla (Kim et al, 2000) and Tea (Park et al., 2002).

    Identification of Pratylenchus species is usually based on shape and measurement of female (Corbett, 1969; Frederick and Tarjan, 1989; Handoo and Golden, 1989). Small number of diagnostic characters and the intra specific variability makes the species identification difficulty (Taylor and Jenkins, 1957; Roman and Hirschmann, 1969). And we have little information of exotic species. Therefore the goal of this study is to provide identification information about exotic nematodes. Finally it will contribute to improving the identification rate of intercepted exotic root-lesion nematodes.

    Materials and Methods

    Total 18 exotic examples are used to identification (Table 1). The nematode was collected from the roots of imported crops. The plant cut into small bits and soak in water over 12 hours. After then the nematodes were extracted by Cobb’s sieving and gravity method (Cobb, 1918; Sauthey, 1986) and modified Bermann funnel method. Extracted nematodes were into the water and killed by heating. They were dehydrated by rapid lactophenol method (Franklin and Goodeyi, 1949). Fixed nematodes were brought into glycerin and sealed by paraffin ring method (De Maesener and De Herde, 1963). Identification of species conducted under the Zeiss M1 light microscope. Photographs and measurements from the specimens were conducted using Axiovision 4.7 microscopy software. Dichotomous key suggested by Pablo Castilo and Nicola Vovlas were used (Castilo and Vovlas, 2007). Measurements are described De Man (1880) formula (Table 2).

    Results

    Pratylenchus crenatusLoof, 1960 (Fig. 1)

    Measurements

    Female (n=2): L=511-574 μm; a=22.8-24.8; b=7.3; b’=5.5; c=19.5-20.8; c’=1.9; V=81.5-81.7%; stylet=16.8 μm

    Diagnosis

    Labial region with three annuli. Body annulation prominent. Excretory pore 81.2 μm from anterior end. Spermatheca rounded, empty. Lateral field with four lines. Post-vulval uterine sac short (16.8-19.6 μm). Distance between vulva and anus 60.9- 88.9 μm. Tail broadly rounded, often spatulate, 24.5-29.4 μm long. Tail tip coarsely and distinctly annulated with 24-26 annuli.

    Host

    Dicentra spectabilis (bulb)

    Remarks

    The length of post-vulval uterine sac was differently described by several nematologists. Loof(1960) indicated that their post-vulval uterine sac is short and Sher & Allen(1953) reported that it is two body diameter long. This study is based on Loof’s concept.

    Pratylenchus fallax Seinhorst, 1968 (Fig. 2)

    Measurements

    Female (n=4): L=469-560 μm; a=21.6-22.7; b=5.2-5.8; c=17.0-20.0; c’=2.1-2.4; V=79-81%; stylet=16.8-17.5 μm

    Diagnosis

    Labial region with three annuli. Stylet knobs anteriorly flattened or pointing forward. Lateral field with four lines. Excretory pore 79.8 μm from head end. Post-vulval uterine sac 11.2-20.3 μm long. Spermatheca round, filled with sperm. Distance between vulva and anus 77-80.5 μm. Tail conical, 26-32.2 μm long, annulated with 19-24 annuli. Tail tip rounded, slightly crenate.

    Host

    Dicentra spectabilis (bulb)

    Remarks

    The species is close to P. penetrans, but it can be differentiated by crenate tail terminus

    Pratylenchus kumamotoensis Mizukubo, Sugimura & Uesugi, 2007 (Fig. 3)

    Measurements

    Female (n=3): L=581.8-612.3 μm; a=24.08-30.86; b’=4.7; c=20.0; c’=2.2; V=77.9-78.7; stylet=13.6-15.4 μm

    Male (n=2): L =469.5-490.8 μm; a=24.45-27.65; spicules= 18.78 μm

    Diagnosis

    Female: Lip region with three annuli. Stylet knobs rounded. Lateral field with four lines. Pharyngeal gland lobes overlapping intestine ventrally or dorsally. Post-vulval uterine sac 42-49.6 μm long. Spermatheca oval, filled with sperm. Tail conoid, 30.66 μm long.

    Host

    Citrus unshiu (seedling)

    Remarks

    The species showed variation in overlapping with pharyngeal gland lobe and intestine. The nematodes of belonging to the genus Pratylenchus overlap intestine ventrally, but P. kumamotoensis sometimes overlaps intestine dorsally. Our specimens show that these characters, we identified them as P. kumamtoensis. It is recorded on Chrysanthemum morifolium only, but we detected from Citrus unshiu.

    Pratylenchus panamaensis Siddiqi, Dabur & Bajaj, 1991 (Fig. 4)

    Measurements

    Female (n=4): L =470-580 μm; a=16.8-28; b=5.3-7.3; b’= 4.3-5.1; c=16.9-23.1; V=76-85%; stylet=16.5-18.2 μm

    Diagnosis

    Body straight or slightly curved ventrally when heat-relaxed. Labial region flat, low and offset from body with two annuli. Stylet knobs anteriorly flattened. Lateral fields with four equidistance lines. Opening of dorsal pharyngeal gland 2-3 μm from stylet base. Median bulb well developed. Pharyngeal gland lobe overlapping intestine for 1.5-2 body diameter long. Excretory pore 60-88 μm from anterior extremity. Spermatheca longitudinally oval filled with sperm. Post-vulval uterine sac 18-25 μm long. Tail sylindrical, with distinctly crenate terminus.

    Host

    Epimidium koreanum (bulb)

    Remarks

    The examined specimens were collected Epimidium koreanum in U.S.A.. According to Siddiqi, Dabur and Bajaj (1991), however, the species is distributed in Panama and parasites on Coffee sp..

    Pratylenchus penetrans (Cobb, 1917) Filipjev & Schuurmans Stekhoven, 1941 (Fig. 5)

    Measurements

    Female (n=2): L=609-647.5 μm; a=23.5-25.6; b=5.8-7.5; b’=4.6-5.4; c=18.9-23.1; c’=2.1; V=78.3-80%; stylet=16.8- 17.5 μm

    Male (n=1): body length=448 μm; a=25.6; c=17.7; stylet= 15.7 μm; spicules=15.4 μm; gubernaculums=4.2 μm

    Diagnosis

    Female: Labial region slightly offset from body, low, with three annuli. Excretory pore 92.4-93.8 μm from anterior end. Pharynx overlapping ventrally or laterally. Spermatheca rounded, filled with sperm. Post-vulval uterine sac short and undifferentiated. Tail generally rounded, 28-32.2 μm long. Tail tip smooth.

    Host

    Dicentra spectabilis (bulb)

    Remarks

    This species characterized by labial region with three annuli, short post-vulval uterine sac and round tail.

    Discussion

    The species identification of nematodes is based on morphological characters, but, due to wide range of variation in diagnostic characters (Andres et al., 2000; Yu et al., 2012), variable features must be integrated for identification. Thus, it caused serious time-consuming and requires expert knowledge (Kumari et al., 2004; Devran and Sogut, 2009). In quarantine inspectsion, especially, detected nematodes were mostly nonnative species, and it was difficult for full identification.

    Pratylenchus species are parasites on roots of economic plants, and often detected during quarantine inspection (Handoo et al., 2001; Ranjan, 2005; Zhang et al., 2011). In this study, five species, P. crenatus, P. fallax, P. kumamotoensis, P. panamaensis, and P. penetrans were found from imported plants into Korea. In distribution, only one species, P. penetrans is inhabited in Korea (Castilo and Vovlas, 2007). And in species identification, it was known that P. kumamotoensis showed variation in diagnostic characters of genus level (Mizukubo et al., 2007). For resolving of these problems, morphological diagnoses of above five species were clearly described. Therefore, our results might lead to increase full identification rate and decrease time-consuming.

    Figures and Tables

    KSAE-53-51_F1.gif

    Pratylenchus crenatus female. A-B: Labial region; C: Spermatheca; D-E: Tail.

    KSAE-53-51_F2.gif

    Pratylenchus fallax female. A-C: Labial region; D-E: Spermatheca; F-H: Tail.

    KSAE-53-51_F3.gif

    Pratylenchus Kumamotoensis female: A: Labial region; B: Pharyngeal region; C: Spermatheca; D: Vulva and post uterine sac; E: Tail.

    KSAE-53-51_F4.gif

    Pratylenchus panamaensis female A: Labial regon; B: Pharyngeal region; C: Egg and spermatheca; D: Spermatheca and vulva; E: Lateral field at mid-body; F: Lateral field at tail; G-H: Tail.

    KSAE-53-51_F5.gif

    Pratylenchus penetrans female: A: Labial region; B-C: Spermatheca; D-E: Tail.

    A list of root-lesion nematodes intercepted on plant quarantine inspection

    Abbreviated form of measurements (De Man formula)

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    Vol. 40 No. 4 (2022.12)

    Journal Abbreviation Korean J. Appl. Entomol.
    Frequency Quarterly
    Doi Prefix 10.5656/KSAE
    Year of Launching 1962
    Publisher Korean Society of Applied Entomology
    Indexed/Tracked/Covered By