Description of a new Pratylenchus species from China(Tylenchida, Pratylenchidae)

Ning LIU, Xiao-Song ZHOU, Li-Jie CHEN, Yu-Xi DUAN

Nematology Institute of Northern China, Shenyang Agricultural University, Shenyang 110866, China

Root-lesion nematodes of the genus Pratylenchus(Bajaj & Bhatti, 1984) rank second only to root-knot and cyst nematodes in terms of worldwide economic impact on crops (Sasser & Freckman, 1987). This is due not only to their wide host range, but also their distribution in almost every cool, temperate and tropical environment.Pratylenchus species are obligate biotrophic, soilinhabiting parasites and are found in all agricultural regions of the world (Hunt & Perry, 2007). So far, more than sixty species in the genus have been recorded(Castillo & Vovlas, 2006). Pratylenchus ekrami Bajaj &Bhatti, 1984, belonging to Tylenchida, Pratylenchidae has been recorded only in the soil and roots of Pyrus malus L. at a horticultural farm in India. Body of the genus is open C-shaped upon fixation and becomes thinner from the vulva; labial framework is sclerotized,extending posteriorly up to two body annuli; stylet is 11-13 μm long and the tail is conoid (Bajaj & Bhatti,1984). One species was found from maize (Zea mays)roots in Shenyang and luffa (Luffa cylindrica) roots in Dalian, China. It was identified as P. ekrami after morphological studies, and is reported here for the first time.

MATERIALS AND METHODS

All specimens used in this study were obtained from the soil of maize roots in Shenyang and luffa roots in Dalian, Liaoning Province, which are the first reported occurences of this species in China. Soil samples were dissociated by sucrose centrifugation(Chen et al, 2007). Specimens were fixed in FG (8 mL 40% formaldehyde, 2 mL triethanolamine and 90 mL sterile water) for measurement and photographs.1First,these specimens were placed on permanent slides. The shape of the females was then observed directly using optical and biological microscopes. The fine structure was observed by using an oil immersion lens.Photographs were taken and features were measured using motic metrology software. Good photos were selected to be drawn.

RESULTS

Pratylenchus ekrami Bajaj & Bhatti, 1984, a new record species in China (Figure 1).

Measurements

Female (n=10): L=422.0-490.0 (449.9±25.20) μm,W=13.7-20.2 (16.9±2.43) μm, a=21.7-33.3 (26.4±4.46),b=5.2-6.7 (6.03±0.47), b'=3.4-5.2 (4.5±0.85), c=15.3-22.6 (18.88±2.34), c'=1.6-2.2 (1.83±0.26),V=79.9%-83% (81.58±1.07), stylet=11.2-13.1(12.23±0.74) μm, Tail=18.7-28.3(23.48±3.13) μm.

L: body length; W: greatest body width; a: body length/greatest body width; b: body length/distance from anterior end to junction of oesophagus and intestine; b':body length/distance from anterior end to oesophagus end; c: body length/tail length; c': tail length/anus body width; V: distance from vulva to anterior end×100/body length.

Description

Female: Body opened C-shaped upon fixation. The body became slender from vuval region. Lateral fields with four lines extended to tail terminus. Labial region was continuous with the rest of the body, anteriorly truncate, and had three annules. Labial framework was sclerotized, extending posteriorly up to two body annuli.Stylets were 11-13 μm long with rounded, sloping knobs. Corpus was long, almost cylindrical. Median bulb was oval. Pharyngeal gland overlapped the intestine. Opening of dorsal was 3-4 μm from stylet base. Nerve ring was located at mid-isthmus. Excretory pore was 74-79 μm from anterior extremity. Hemizonid was just anterior to excretory pore. Spermatheca was elongated oval and filled with sperm. Vulva was a transverse slit located at 77%-83% of body length. Tail was elongated conoid or blunt.

Male: Not found.

Figure 1 Illustrations of Pratylenchus ekrami

DISCUSSION

Pratylenchus ekrami was close to Pratylenchus vulnus,although they differed in shape of labial region, number of lip annuli, stylet size, shape of stylet knobs and median bulb,details of lateral lines and number of tail annuli.Pratylenchus ekrami is characterized by: labial region continuous with rest of body, anteriorly truncate, three annuli, stylet 11-13 μm long with rounded, sloping knobs, tail tip narrowly to broadly rounded. The characteristics of P. vulnus are labial region high, lip annuli usually three or four on one side and four on the other, stylet 14-18 μm long, stylet knobs rounded, central band of lateral lines narrower than outer ones, median bulb oval, relatively narrow.

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