Identification of Plant Parasitic Nematodes Infecting

Plant parasitic nematodes belonging to twelve genera viz. , Hoplolaimus, Xiphinema Tylenchorhynchus, Tylenchus, Helicotylenchus, Ditylenchus, Psilenchus, Aphelenchus, Pratylenchus, longidorous, Aphelechoides and Paralongidorous along with free living soil nematodes have been isolated and identified. Root knot and cyst nematodes from root samples have also reported. INTRODUCTION Dargi, Malakand area is heavily infested by all groups of nematodes i. e.

parasitic, free living, and predacious, including root Knot and cyst nematodes.

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These nematodes infect all crops in the region directly or by transmitting other diseases as vector which increases the infestation rate. During 1984 to 1988 the nematodes infestation increased to such a level that tomato and other solaneceious crops fail to grow in the whole Malakand and Swat Region (Ali khan and Haji Muhammad Agricultural Officer Dargi). Therefore a survey was conducted to isolate and identify the plant parasitic nematodes infecting vegetables particularly and other crops in general in Dargi region. Seven localities i. e.

Jaban, Jabban Turbala Pull, Dobbandi, Warteer, Heroshah, Palona, Muhammad Patti, were visited and soil with root samples have been collected from different host crops like bringle, lady figure, tomato, potato, onion, sponge guard, bottle guard and chilli. The samples were brought to National Namatological Research Centre, University of Karachi, Karachi for detail processing and studies. Nematodes belonging to twelve genera i. e. , Hoplolaimus, Xiphinema, Tylenchorhynchus, Tylenchus, Helicotylunchus, Ditylenchus, Psilenchus, Aphelenchus, Pratylenchus, Longidorous, Aphelechoides and Paralongidorous have been identified.

Two genera have also been identified up to species level i. e. , Hoplolaimus seinhorsti Luc, 1958 and Tylenchorhynchus nudus Allen, 1955. Measurements and drawings of these two species are included in report. Species of Xiphinema act as vector of soil-borne viruses, Hoplolaimus infection increases with combination of fungi (Fusarium oxysporam).

Along with parasitic nematodes large numbers of free-living and predaceous nematodes have also been observed; majority of them belonging to Dorylaimids, Rhabditids, Cephalobids, Acrobeloides sp. Mononchids, the predaceous groups. Heavily infestations have been found in Jabban and Dobbandy area.

Soil moisture (45%—-65%) and soil texture (Clay to sandy clay) has been calculated in June in Dargi region which increased in winter season, both of them are favorable for the nematodes reproduction. During the survey it has also been observed that the infestation of nematodes in the less infected areas increase by the use of irrigation water of infested area.

MATERIALS AND METHODS For taxonomic studies of stylet bearing nematodes, a survey of infecting vegetables in Dargi region, was conducted and twelve soil and root samples were collected from seven localities and processed as ascribed below: . Collection of samples from fields: Soil samples were collected to near the root zone of the vegetables with fine feeder roots randomly from infected fields. After thorough mixing of 1 kg soil samples from each locality was placed in the polyethylene bag, labeled and data have been taken, bearing detail about the field, locality and date of collection and stored at 4 oC temperature. 2. Processing of samples: Soil samples were processed by modified Bearmann funnel method (Bearmann, 1917).

One kg of soil sample was put in a large bucket containing water and the mixture was vigorously stirred into a suspension, which was allowed to settle for about two minutes. The heavy soil particles sank to the bottom but nematode remained suspended in the water. The remaining suspension was slowly poured over a coarse sieve (100 mesh aperture) which was continuously tapped by hand to avoid blocking. The deposits on the sieve was then washed with a gentle jet of water into a beaker. This was examined for the presence of cyst nematodes.

The water suspension containing eel shaped nematodes was then passed through 200 and 300 mesh sieves.

The nematode suspension was then poured over a piece of tissue paper attached to a perforated plastic sheet place in a funnel fitted with a rubber tube and clamped at the lower end. The water contained in the funnel barely touched the bottom of the tissue paper. After 48 hours the nematodes wriggled out into the clear water in the funnel and settled at the bottom, 100 ml of water containing nematodes were drawn in to a beaker. 3. Quantitative analysis: For quantitative analysis a 5 ml nematode nematodes suspension was examined under a stereo microscope and nematodes were counted in a counting chamber.

At least three reading were taken to calculate the average number of nematodes in 100 ml of suspension. The nematode population of per gram of soil was calculated as given in Table (1). 4. Qualitative analysis: For qualitative analysis the nematode suspension was allowed to settle for two hours or more. The excess supernatant water was poured off, the remaining concentrated contents were transferred into a cavity block for examination under a stereo microscope. 5.

Temporary Mounts: For qualitative analysis, observation was made on temporary mounts with a use of stereo microscope.

The small drop of nematode suspension were placed on a 3×1 inch glass slide. Cover slip was placed over a drop on the slide and then sealed with a zut. 6. Killing, fixing and processing of nematodes: To obtained good specimen for taxonomic studies nematodes were killed by heating in a oven at 60 oC avoiding overheating. Specimens were immediately fixed and preserved in a solution of 3% formaldehyde and 2% glycerin.

They were later placed in a TAF (Triethanolamine 2%, 7 ml formaldehyde 38%, 91 ml distilled water) for 24 hours (Courtney, Polly and Miller, 1955).

Fixed nematodes were then processed to glycerin by a slow dehydration method. The specimens were placed in a cavity block containing 2 ml of 1. 25% glycerin solution and traces of picric acid. The cavity block was placed in an incubator at 55 oC for 5-6 days. 7.

Permanent slide mounts: The nematodes were placed in the centre of the slide in a small drop of glycerin. Paraffin wax (62-65 oC) was placed as a four small lumps around the drop in a 19 mm diameter, cover slip on the wax lumps. The slide was then gently heated on a hot plate to melt the wax and filled the space between the slide and cover slip.

Slides were finally sealed by ringing the cover slip using Zut, (Siddiqi, 1986). Measurements were taken by the means of ocular disk micrometer in a compound microscope and illustration was made with the help of a drawing tube.

8. Photomicrograph of eelworm and cyst nematodes: For light microscopy (LM) the fixed nematodes were processed using methods of Hooper (1970) and Golden (1978). Photomicrograph of eelworm, cyst, vulval cone, female, male and juveniles were made with an automatic camera attached to a compound microscope equipped with an interference contrast system. 9. Measurements and Drawings:

The illustrations were prepared with the help of a drawing tube. RESULTS AND DISCUSSIONS From seven localities of Dargi-Malakand twelve soil samples have been collected.

Number of parasitic nematodes belonging to twelve genera i. e. Hoplolaimus, Xiphinema Tylenchorhynchus, Tylenchus, Helicotylunchus, Ditylenchus, Psilenchus, Aphelenchus, Pratylenchus, Longidorous, Aphelechoides and Paralongidorous have been isolated and processed for detail taxonomic studies. As a result of quantitative and qualitative analysis as given in Table (1) number of nematodes in each locality per gram of soil has recorded as 0. 6-0. 18.

Soil moisture was in range of 45-70% and soil texture was sandyclay-clay. The percentage of each genera was calculated in each locality given in Table (2). Helicotylenchus species was found in every locality followed by Xiphinema, Pratylenchus, Ditylinchus Tylenchorhynchus, Tylenchus, Psilenchus, Aphelenchus, longidorous, Aphelechoides and Paralongidorous. Large number of free-living and predacious nematodes have also been observed and given in Table (3) as extra information. Dorylaimids were recorded from each locality.

Cyst (Heterodera spp. ) has also recorded from two localities i. . Jabban & Palona area. Pictures are included in report.

The frequency of occurrence of each plant parasitic genera was also calculated and given in Table (4). Our finding confirmed that Dargi region is heavily infested by plant parasitic, free-living, predacious, cyst and root-knot nematodes. Not only they directly and indirectly infected the crops but also act as a vector of transferring diseases viral, bacterial and fungal etc. Therefore it is absolutely necessary to take care for the control of these nematodes as they are pathogenic to plants not only but harmful to human being. Table 1.

Qualitative and Quantitative analysis of plant parasitic nematodes S.

No. | Locality| Soil Type| Soil moisture| No. of nematodes per gram| Genera isolated| 1. | Jabben Turbela Pull| Clay| 44-45%| 0. 86| Pratylenchus XiphenemaTylenchorhynchus HelicotylenchusDitylenchus| 2.

| Jabben| Sandy- clay| 40-45%| 0. 33| HelicotylenchusPratylenchus XiphinemaTylenchorhynchusTylenchusHoplolaimus| 3. | Dobandy Varteer| Sandy- clay| 50-55%| 0. 16| DitylenchusTylenchorhynchusHelicotylenchusPsilenchus| 4. | Dobandy| Clay| 50-55%| 0. 88| HelicotylenchusPratylenchus XiphenemaTylechusDitylenchusAphelenchus| 5.

| Dobandy 2| Clay| 40-50%| 0. 5| HelicotylenchusPratylenchus XiphenemaTylenchusHoplolaimusDitylenchusAphelenchus| 6. | Palona| Sandy- clay| 45-50%| 0. 34| HelicotylenchusXiphenema| 7. | Heroshah| Sandy- clay| 50-70%| 0.

43| HelicotylenchusPsilenchusAphelenchusTylenchusHoplolaimusXiph enema| Table 2. Qualitative and percentage analysis of plant parasitic nematodes. S. NO| Locality| Genera Isolated| Percentage| 1. | Jabban Pull| Pratylenchus XiphinemaTylenchorhynchus HelicotylenchusDitylenchus| 4. 3%4.

2%8. 5%10. 6%4. 2%| 2. | Jabban| HelicotylenchusPratylenchus Xiphinema| 20. 715.

912. 5| 3. | Dobandy Vertar| DitylenchsTylenchorhynchusHelicotylenchusPsilenchus| 14. 19. 119. 17.

1| 4. | Dobandy| HelicotylenchusPratylenchus XiphinemaTylenchusDitylenchusAphelenchus| 2. 914. 912. 812. 813.

85. 9| 5. | Dobandy 2| HelicotylenchusPratylenchus XiphinemaTylenchusHoplolaimusDitylenchusAphelenchus| 25. 410. 93. 65.

45. 412. 77. 2| 6. | Palona | HelicotylenchusXiphinema| 26.

622. 2| 7. | Heroshah| HelicotylenchusPsilenchusAphelenchusTylenchusHoplolaimusXiph inema| 22. 53. 64. 52.

734. 28. 1| Table. 3. Qualitative and percentage analysis of free-living nematodes S.

NO. | Locality| Free Living Nematodes| Percentage | 1. | Jabban Pull| DorylaimidsCephalobidsAcrobeloidesRhabditids| 25. %34. 0%4.

2%5. 2%| 2. | Jabban| DorylaimidsRhabditidsCephalobids| 25%6. 8%7. 9%| 3. | Dobandy Vertar| DorylaimidsCephalobids| 16.

2%23. 8%| 4. | Dobandy| MononchidsDorylaimids| 8. 9%15. 8%| 5.

| Dobandy 2| DorylaimidsCephalobidsRhabditids| 20%7. 2%10. 9%| 6. | Palona | DorylaimidsRhabditids| 35. 5%15.

5%| 7. | Heroshah| DorylaimidsRhabditids| 16. 2%8. 1%| Table 4. Frequency of occurrence of plant parasitic nematodes in each locality S. NO.

| Genera isolated| Frequency of Occurrence (%)| 1. | Pratylenchus| 57%| 2. | Xiphinema| 71%| 3. | Tylenchorhynchus| 28%| 4. | Helicotylenchus| 100%| 5.

| Ditylenchus| 57%| . | Aphelenchus| 28%| 7. | Hoplolaimus| 28%| 8. | Tylenchus| 28%| 9. | Psilenchus| 14%| 10.

| Root knot juveniles| 14%| FAMILY HOPLOLAIMIDAE (Migratory ectoparasitic Hoplplaimoidea) This is large family of economically important Tylenchida. It comprises three sub-families—Hoplolaiminae, Aohasmatylenchinae and Rotylenchoidinae, which have slender females which are migratory ectoparasitic of roots, but some have a tendency to bury themselves in roots. Unlike Prtylenchidae, they are seldom able to move freely with in the roots tissues and have failed to colonize them, their juveniles and adult occurring in soil.

The Hoplolaimidae penetrate root tissue intercellularly and reach the inner layers of the cortical tissue by thrusting of the stylet and then the interior end of the body, but they do not establish a permanent feeding site by inciting giant cells. Basically they are ectoparasitic; Helicotylenchus multicinctus feed from a single root hair cell for 40min, or up to 19 days on deep cortical cells with alternating salivation and ingestion and thus show an evolutionary tendency towards sedentary root parasitism.

Hoplolaimus galeatus parasitizes several field cops (cotton, lucerna, carrots, lettuce, pea and other vegetables).

The infestation rate increase with the presence of Fungi Fusarium oxysporum and other plant pathogenic fungi. Genus Hoplolaimus Daday, 1905 Diagonosis Hoplolaiminae. Large sized (1—2mm). Lateral field usually with two or four incisures, sometime obliterated.

Cephalic region offset, rounded, marked by prominent transverse and longitudinal striae; labial disc distinct; basal annule marked by more than six longitudinal striea; framework very heavily sclerotized. Stylet massive, with compact tulip type _shaped basal knobs having one or three anterior tooth like projection.

Excretory pore near hemizonid or more anterior. Epiptygma present, often indistinct. Oesophageal glands large, overlapping intestine dorsally and laterally; dorsal gland uni or quardrinucleate. Phasmid large, scutellum like, not opposite each other, one prevavlval and other postvuvlval (except H.

californicus in which both phismids are postvuvlval). Female tail hemispherical, annulated. Spicules massive, somewhat cylindroids, may be dimorphic with distal flanges variable in size. Gubernaculam large, protrusible, with titillate and telamon. Species Found Hoplolaimus seinhorsti Luc, 1958

Female: Lip region with usually four annules. Basal annules of lip region with eight to twelve longitudinal striations (eight face views).

Spear knobs with usually two pointed anterior projecting processes. Oesophagous glands with six nuclei. Excretory pores usually at level of isthmus of oesophagous. Hemizonid five to ten anterior or below excretory pore, hemizonion five to ten annule below hemizonid. Hemizonid and hemizonion often two structure at different levels in the body. Epiptygma usually single connected anteriorly or posteriorly.

Intestine does not overlap rectum. Spermatheca absent.

Single incisures on body often in distinct. Tail round with ten to fifteen annules. Measurment: 2 ++ L = 1143 um, a = 31.

9-36. 9, b = 9. 5-10. 9, b’ =7. 1-8. 5, c = 51-55.

4, c’ = 43. 3-50. 3, v% = 52. 4- 57. 4 %, G1 = 25-20.

3, G2 = 23-20. 7, stylet = 45-48, anterior phasimd = 356- 306 Male. Not Found Remarks. Collected from soil of onion from Dargi Malakand area, Khyber Puhtoon khwa. The specimens were examined and identified as Hoplolamus seinhorsti Luc, 1958. All measurements were similar as given by Luc (1958).

Genus Hilicotylenchus steiner, 1945 Diagnosis Small to medium sized (0. 4—1. 2mm).

Females spirally coiled or rarely arcuate, cephalic region low or elevated, continuous or rarely offset, with or without annulations; no longitudinal indentations on annules. Stylet robust, about three to four times maximum width of cephalic region.

Orifice of dorsal oesophageal gland one forth to a little more than half of stylet length behind base of stylet. Post corporal bulb well developed, usually slightly offset from precorpus (styley and bulb reduced in some male species). Excretory pore behind hemizonid, near base of isthmus. Oesophageal glands forming a wraparound over anterior end of intestine, longest overlap being ventral.

Oesophago intestinal junction with a small cuticular valvula.

Intestine rarely with fascicule; not overlapping rectum. Both branches of female reproductive organs well developed and functional. Female tail short, hemispherical, dorsally convex-conoid, with or without a ventral or terminal projection. Male tail short(less than two anal body widths), conical, with a distinct terminal hyline portion. Bursa enveloping entire tail tip, rarely subterminal.

Gubernaculums trough or rod shape, fixed; talemon SUPER FAMILY LONGIDOROIDEA, THORNE, 1935 0apparatus and the characteristic type of oesophageal bulb and oesphageal gland orifices.

Since the report of Hewitt, Raski and and Goheen (1958) that Xiphinema index acts as a vector of soil-born viruses, much attention has been paid to this group of the nematodes, resulting in the description of a large number of species of various genera from different parts of the world. Xiphinema is the most commonly found genus of logidorids and is represented by a large number of spices exhibiting variation in several body structures. Dalmasso (1969) divided Xiphinema in to four groups i. e. X.

americnum, X. basiri, X. diversicaudatum, X. italiae group. Cohn and Sher (1972) proposed eight sub-genera of Xiphinema.

Superfamily Longidoroidea Thron, 1935 Digonosis; Body slender, large sized, 1-12mm long. Lip region continuous or offset. Amphids with large pouch, funnal or stirrup-shaped fovea and pore or slit-like aperture. Odontostyle long and attenuated, with fine lumen and aperture. Odontophore simple, rod like or with basal flanges.

Odontostyle- odentophore junction simple or complex. Guiding ring single or double. Oesphagus with an anterior non-muscular convoluted tubular part set off from an expanded muscular part comprising about one forth of total oesophageal length. Female reproductive system monodelphic or amphidelphic. Vulva transverse.

Spicule arcuate, lateral guiding pieces and ventromedian supplements present. Tail similar in sexes. Genus Xiphinema Cobb, 1913 Diagnosis. Body long and slender, 1-6 mm. lip region continuous or slighty to markedly set off from body.

Amphids with stirrup shape fovea and slit like aperture. Odontostyle long and attenuated, forked at junction with odontophore. Guiding apparatus appearing tubular, fixed ring located at base of odontostyle. Odontophore with well developed basel flanges. Expanded part of oesophagus about one third of total oesophageal length.

Female reproductive system monodelphic or pseudo monodelphic or amphidelphic.

Z organ may present in uterus. Males with dorylaimoid spicules, tail greatly variable in shape and size may short, conoid to long filiform, similar in sexes. FAMILY ANGUINIDAE (Fungal feeder and parasites of aerial parts of plant) The families differs from the Hexatylina in lacking an entomoparacitic phase in the life history and form the Tylenchina in being fungal feeders and parasites of the aerial parts of plants. Like Hexatylina, the ancestral trait of the Anguinidae is fungal feeding. A number of genera contain species which are economacallly important plan parasites.

Anguina tritici (wheat gall nematode) was the first plant parasities nematode to be recorded. Upon soaking the nematodes revive and attack the plant and reach to the aerial parts as the plant grows, by moving through water films on the exterior or migrating through the plant tissues. Anguina tritici may feed ectoparasitically on the growing plants and leaf bases until it is able to enter the inflorescence. As the embryo seeds are formed, the nematodes invade them and the adult feed and meet inside the grain. The female lays a large numbers of eggs (a few hundred to 32000). The adult die in the grian, hose entire cavity is then occupied by the second stage juveniles.

Ditylenchus dispsaci, popularly called stem nematodes or stem and bulb nematodes, attack over 450plants and is pathogenic to variety of crops such as onion, ray, maize, oats, beans, lucerna, strawberry etc. the nematodes are migratory endoparasitic and causes dissolution of middle lamella of the cell walls so that become detached and tissue swells. The life cycle on onion is completed in 19-23 days. A few species of the D. triformis group are also important.

Ditylenchus destructor, the potato tuber or potato rot nematodes, is noted as an important pest of potato and bulbous.

Ditylenchus myceliophagus is important because it destroy the mycelium of the cultivated mushrooms, Agaricus biporus. Peak populations of the nematodes are found shortly before the last mycelium is killed. The nematodes migrate, but if there is not enough moisture, the congregate in masses on the mushroom culture boxes, on the casing or they many hung down like miniature stalacities. The nematodes is controlled by the pre treatment of compost after lifing the crop, however nematodes of this group are not parasites of the aerial parts of the plants as compared to the D.

dispsaci group.

Genus Ditylenchus Filipjev, 1936 Diagnosis Anguininae. Body usually under 1. 5 mm long, not curing strongly when relaxed; mature adults slender. Lateral field with four or six (occasionally more) incisures, which may be indistinct.

Median bulb muscular or non-muscular, with or without refractive. Median bulb muscular or non-muscular, with or without refractive thickenings. Isthmus not marked of from basal bulb. Basal bulb a thin elastic sack containing esophageal gland, base of bulb may extended over intestine but the nuclei of gland remain within the bulb anterior to esophago-intestinal junction.

Intestine with two normal-sized but often hyaline cells at its anterior end possibly acting as a vulva; lumen of intestine not considerably narrow an anterior region.

Ovary out stretched, with one or two rows of oocytes. Crustaformeria in form of a quadricolumella of four rows of four cells each. Spermatheca elongate axial sc. Vagina at right angle to body axis or nearly so, or not directed forward. Post vulval uterine sac present. Testis outstretched bursa adanal to sub terminal never enclosing tail tip.

Tails elongate conoid to sub cylindrical or filiform.

Fungal feeders and parasitic of higher plants, several species including the type species are capable of attacking aerial parts. FAMILY TELOTYLENCHIDAE (The stunt Nematode) The stunt nematodes, e. g. Tylenchorhynchus, Quinisulcius, Merlinius and Bitylenchus spp.

, are root surface tissue feeders, polyphagus in nature and are commonly found in vegetables fields, grasslands and forest soils. Tylenchorhynchus ewigi and T. claytoni cause stunting of root tips, chlorisis and retarded growth, sometime result in death of forest tree seedling in nurseries (Hopper, 1959).

Tylenchorhynchus claytoni reduces the root system of barley, maize, cotton, oat, potato, soybean, etc. , causing damages to the crops.

It is bisexual and completes its life cycles in about a month. Diagnosis Telotylenchinae. Amount 1 mm or less long. Cuticle prominently annulated may be marked by longitudinal striae, longitudinal ridges or lamellae outside lateral fields absent; not abnormally thickened on tail. Lateral field with three or four incisures, generally not areolated behind oesophageal region.

Cephalic region offset from body (type genus) or continuous, annulated, or rarely smooth, without longitudinal indentations on annules; labial disc indistinct, in SEM en face squarish, flattened, fused with first lips annules; framework light to moderately sclerotized. Stylet well developed, generally 15-25 µm long; conus anteriorly solid appearing; knobs prominent. Median bulb round or oval, with distinct refractive thickenings, usually marked off from pre corpus and isthmus. Basal bulb offset from intestine, or base slightly extending over intestine. Cardia prominent.

Vulva near middle of body, generally at 50-54%, lips not modified. Spermathecae round, axial. Ovaries paired, outstretched. Female tail usually conoid with blunt tip as in type species, but may be subcylendroid, cylendroid or subclavate; terminus smooth, rarely striated or narrowing to a point. Males generally present. Tail enveloped by a large simple bursa.

Spicule distally flanged, terminus narrow, indented or pointed. Gubernaculum well developed, about half as long as spicule, generally rod-like and with a velum, protrusible. Cyst (Heterodera spp. ): Cyst light to dare brown, lemon shaped, with protrudins neck and vulva.

Cuticle zig-zag pattern conspicuous irregularly arranged, sub cuticular punctuation present. Egg sac absent.

Cone to abullate, ambifenestrate. Cyst reported from the sample No. 8 (Jabban Area) and sample No. 3 (Polana Area) processed and found it is Heterodera genera pictures of cyst, egg and juvenile are given as. FAMILY PSILENCHIDAE The family Psilenchidae has members looking like those in Tylenchidae, particularly in the weak stylet and elongate tail, but the didelphy and the presence of phasmids on the tail clearly differentiate between the two families. Luc et al.

(1987) and Ryss (1993) regarded Psilenchus, Atetylenchus and Antarctenchus as representing the most primitive taxa of Tylenchida. Sturhan & Rahi (1996) stated that the placement of these genera into a separate, though obviously paraphyletic taxon, Psilenchidae in Dolichodoroidae, as done by Siddiqi (1986) and Ryss (1993), instead of keeping them in closer systematic relationship to Tylenchidae and Anguinidae, appeared more justified. Genus Psilenchus de Man, 1921 Diagnosis Psilenchinae. Body 0. 7-1.

7 mm long, usually curved upon relaxation. Lateral fields each with four incisures, inner two may be indistinct or absent.

Amphidial apertures transverse, slit-like, at base of lateral lip areas. Phasmids distinct, on tail, anterior to its middle. Cephalic region elevated, rounded or conoid, smooth or striated; framework slightly sclerotized, with conspicuous outer margins extending in to body. Stylet cylindrical, 10-24 µm long, conus distinctly shorter than shaft, basal knobs absent.

Median bulb prominent, generally oval, usually behind middle of oesophagus. Basal bulb small, pyriform; cardia discoidal or rounded. Vulva near middle (V=45-53), lacking epyptigma and lateral membrance. Ovaries paired, out-stretched in opposite directions.

Spermathecae elongate, axial.

Tail elongate, with clavate or non-clavate rounded tip. Bursa prominent, adanal. Sperm rounded, moderately large. Spicule tylenchoide, 25-33 µm long. Gubernaculum simple, trough shaped, fixed. FAMILY PRATYLENCHIDAE This family contains elongate-slender nematodes with a low-arched, strongly sclerotized, cephalic region generally with two to three annules, well-developed styles usually not more than three head widths long, moderate-size tails and oesophageal glands overlapping intestine with the subventrals extending past the dorsal gland.

Juveniles, females and the males in some groups (Pratylenchinae, Hirschmanniellinae), are capable of penetrating and feeding on internal root tissues. Species of Pratylenchus, popularly known as root-lesion or meadow nematodes, are worldwide in distribution. Some species, e. g P. brachyurus, P.

coffeae, P. penetrans, P. zeae, attack and damage several important crops. The damage to the root system is due both to the direct feeding and physical activities of the nematodes, and to their digestive and metabolic secretions. The injury is aggravated by the contamination of the feeding sites with microorganisms.

Several species may interact with pathogenic fungi (e. g. P. brachyurus with Rhizoctonia solani), causing greater damage than by nematodes or fungi alone. Large populations of nematodes build up in roots (over 10,000 Pratylenchus per gram of root of Vicia faba) and once decay sets in, the nematodes migrate through roots or soil to parasitize fresh tissues. Pratylenchus penetrans fed ectoparacitically on root hairs of rape, oil radish, tobacco and potato.

The feeding involved probing, cell penetration by the stylet, salivation and food ingestion.

All stages were observed to feed on root hairs, but adults soon moved into the root to feed indoparasitically (Zunke, 1990). Genus Pratylenchus Filipjev, 1936 Diagnosis Pratylenchinae. No marked sexual dimorphism in anterior region. Lateral fields each with four to six incisures, occasionally with oblique median markings, Deirids absent.

Phasmids near middle of tail. Cephalic region low, flattened anteriorly or rarely rounded, continous with body contour; sclerotization massive; labial disc inconspicuous in SEM dumb-bell-shaped, with six labial disc, indistinct.

Stylet 20 µm or less long, with round, anteriorly flat or indented basal knobs. Median bulb oval to round, very muscular. Oesophageal glands usually less than two body widths long extending over intestine mostly ventrally. Vulva in posterior region (usually at 70-80%).

Pseudo-mono-prodelphic, with only anterior ovary functional Postvulval uterine sac present, with or without rudiments of posterior ovary. Spermatheca large, rounded, usually axial. Female tail subcylindrical to conoid, usually about two to three anal body widths long; terminus smooth or annulated, devoid of a process or mucro.

Bursa enclosing tail terminus. Spicules with-subterminal pore on dorsal side.

Gubernaculum simple, trough-like, fixed. FAMILY TYLENCHIDAE Members of this family are cosmopolitan. They are encountered in large numbers in extractions from soils rich in alage aand mosses. On the evolutionary ladder of modern Tylenchida, they represent the first rung in being both weak plant parasites and as a conservative group with many ancestral characters (e. g.

weak feeding apparatus, undifferentialed non-muscular corpus, filiform tails, etc).

Andrassy (1979) collected representatives of the Tylenchidae from 86 countries, states and islands and Butschli (1873) found Tylenchus davainei and Tylenchus filiformis (now the type species of Filenchus) in soil under moss. Siddiqi & Hawksworth (1982) reported the finding of Ottolenchus cabi in association with a lichen, Caladonia glauca, and speculated that it was finding on the algal part of the lichen. Siddiqi (1983a) regaeded Tylenchidae as weak parasites of plants, several geenra (Tylenchus, Filenchus, Ottolencus) feeding on the soil and freshwater algae and parasitizing lichens and mosses.

They do not cause economic losses to crops.

Genus Tylenchus Bastian, 1865 Diagnosis Tylenchinae. Small to medium sized (0. 4-1. 3 mm), ventrally curved upon relax action. Cuticle moderately thick (1-2 µm), distinctly anuulated. Lateral fields each with four incisures.

Prophasmids dorso-sublateral, post median, just behind vulva. Cephalic region continuous, annulated; framework with light or no sclerotization. Stylet 8-12 µm long, with conus about half (more than one-third) of stylet length; knobs round or posteriorly sloping. Median oesophageal bulb oval, muscular, anterior to middle of oesophagus; basal bulb pyriform.

Cardia distinct.

Excretory pore usually opposite basal bulb. Deirids just behind level of excretory pore. Vulva a transverse slit usually at 60-70% of body length, lips not modified; epiptygma or lateral membranes absent. Vagina generally at right angle at body axis. Postvulval uterine sac about a body width or less long.

Supermatheca round to oval, offset. Ovary outstretched. Tail ventrally arcuate, often hooked, regularly tapering to a pointed or minutely rounded terminus. Bursa adanal margin crenate. Spicule cephalated, arcuate, 13-25 µm long.

Gubernaculum simple, fixed.

Cloacal lips slightly raised, anterior one pointed, posterior usually rounded, not tubular. Hypoptygma absent. Genus Aphelenchulus Cobb, 1920 Diagnosis Contortylenchinae. Entomoparasitic female: Elongate-obese, tuboid, arcuate (not clear if dorsally or ventrally), about 2. 6 mm long; body wall firm, not wrinkled.

Cephalic region more or less rounded,not over grown by body expansion. Stylet knobbed, in normal position. Vulva large, conspicuous, somewhat elevated, especially in front. Uterus straight, with several ellipsoidal eggs, 40 µm x 25 µm, about as long as body width.

Ovary reflaxed at the tip. Tail end convex-conoid, with a conical spike at tip, not directed dorsally.

Oviparous. Juveniles (from host): Cuticle finely but distinctly annulated. Lateral fields with 12 incisures, hardly raised, appearing as somatic body muscles. Cephalic region hemispherical to truncate, slightly offset from body by expansion. Stylet slender, about 8-10 µm long; conus about one-fourthof total stylet length; knobs minute, rounded.

Orifice of dorsal oesophageal gland close to stylet base. Corpus elongate-cylindroid , with fusiform basal swelling.

Isthmus very narrow, enveloped by nerve ring. Basal region of oesophagus and gland obscure. Intestine two-celled in circumference. Rectum less than one anal body width long.

Anus distinct. Tail subcylindroid, bluntly obtuse, terminus with a minute mucro. Partially free-living forms: Male: Body vermiform, 1 mm long. Lateral field with 12 incisures. Cephalic region and stylet as described for juvenile.

Spicules tylenchoid, arcuate, about one and a half times anal body width long. Gubernaculum small, trough-shaped. Tail elongate-conoid, completely enveloped by a bursa.