Host-Parasite Interaction of Resistant Sugarbeet and Heterodera schachtii

The host-parasite relationships between Heterodera schachtii Schm. and the nematode-resistant diploid Beta vulgaris L. line ''51501'' were examined via serial sections of secondary rootlets. Second-stage larvae penetrated sugarbeet roots and migrated up to 1.95 mm before establishing permanent feeding sites. Most sedentary larvae were oriented parallel to the root axis or in various diagonal or folded positions in the cortex. Nematodes adopted no definite orientation with regard to the root apex. Nematode feeding stimulated formation of multinucleate syncytia in host tissues. Syncytia were 0.3-1.1 mm in length, up to 90 [mu]m × 150 [mu]m in cross section. Root diameters were enlarged close to feeding sites. Usually nematodes deteriorated concomitant with necrosis of syncytia, and dead nematodes frequently appeared macerated or flattened and deformed. Most nematodes did not develop to maturity" in the resistant host tissues, Cavities left by collapse of syncytia were filled by growth of parenchymatous tissue.     

Description of Trilineellus clathrocutis n.g., n.sp. (Tylenchorhynchinae: Tylenchida Thorne, 1949) with a Key to Species and Observations on Tylenchorhynchus sensu stricto

TrilineeIlus clathrocutis n.g., n.sp. is described and illustrated. It was found as an associate of corn (Zea mays) in Stockton, Georgia, USA, and is related to a group of Tylenchorhynchus sensu lato species having three lines in nonareolated lateral fields. This new species is closely related to Tylenehorhynehus divittatus Siddiqi 1961, T. sculptus Seinhorst 1963, and T. triglyphus Seinhorst 1963 (syn. T. chonai Sethi & Swarup 1968) Tarjan 1973. It differs from these species primarily by having longitudinal striae on the body. These four species are differentiated from Tylenchorhynchus sensu stricto by having three lateral lines instead of four. They differ from Uliginotylenchus Siddiqi 1971 by having nonareolated lateral fields, fewer than 25 annules on conoid rounded tails, differently shaped gubernacula, nonattenuated stylets, and other distinctive characters. They differ from Triversus Sher 1973 by having the male tail enclosed by the bursa and by having rounded female tails. SEM observations of T. clathrocutis reveal a cuticle deeply cut by longitudinal and horizontal striae and bearing wide (> 2.0 μm) annules. Trilineellus is proposed to accommodate the new species and the three-incisured species still within Tylenchorhynchus. Tylenchorhynchus is thereby the repository for species within Tylenchorhynchinae having four lines in the lateral field, no conspicuous labial disc, and bursa enclosing the male tail.     

Scanning Electron Microscope Study of the Root-knot Nematode (Meloidogyne incognita) on Tomato Root

This study examines the types of structural information that can be gained by utilizing the scanning electron microscope (SEM) and a cryofracture technique to examine the host-parasite interaction. Roots of tomato, Lycopersicon esculentum cv. Marglobe, were cultured aseptically and inoculated with the root-knot nematode, Meloidogyne incognita. Twenty-four hours to four weeks after inoculation, developing galls were removed from the cultures and processed for SEM observation. The cryofracture technique was used to reveal internal structural features within the developing galls. The results illustrate structural details concerning penetration of the roots, differentiation of syncytia, and development of the nematodes beginning with the second-stage larvae and ending with adult egg-laying females.     

Description of Meloidogyne nataliei n. sp. (Nematoda: Meloidogynidae) from Grape (Vitis labrusca) in Michigan,with SEM Observations

Meloidogyne nataliei n. sp. is described and illustrated from grape (Vitis labrusca) in a declining vineyard at Mattawan, Michigan, USA. Infected grape roots exhibit no hyperplastic symptoms. Females protrude from the roots and are surrounded by a massive egg sac containing many eggs. This new species is distinguishable from other species of the genus especially by its large, striking perineal pattern with, usually, two ropelike separated striae on each side extending laterally from the vulval and anal areas. Among other diagnostic characters are the location of the female excretory pore adjacent to or near the base of the head and the heavy larval stylet averaging about 22 μm in length. Examination of males, females, and larvae with the scanning electron microscope confirmed observations made by optical microscopy and revealed diagnostic and other structures in greater detail. Of particular significance was the nature of the male head, with a massive circular labial disc on which is located a rectangular structure surrounding the oral opening, and the six distinct lips appearing as a rosette in en face view. The known distribution of this new species is presently limited to its original location in Michigan.     

Characterization of Citrus Rootstock Responses to Tylenchulus semipenetrans (Cobb)

Citrus rootstocks which significantly limited the reproduction of Tylenchulus semipenetrans (Cobb) "Citrus" and "Poncirus" biotypes responded to infection by producing a hypersensitive-type response in the root hypodermis, wound periderm and/or cavities in the root cortex, and/or abnormal vacuoles in nurse cell cytoplasm. Rootstocks which limited nematode reproduction also had significantly fewer nematodes in the rhizoplane within 8 d of inoculation than did rootstocks which did not limit reproduction. Germplasm sources of the cellular responses which limited citrus nematode reproduction were identified.     

Interrelationship of Meloidogyne hapla and Ditylenchus dipsaci on Resistant and Susceptible Alfalfa

Simultaneous inoculations of alfalfa with Meloidogyne hapla larvae and Ditylenchus dipsaci at 16, 20, 24, and 28 C did not depress penetration of either nematode in ''Nev Syn XX'' -a selection resistant to M. hapla and D. dipsaci, ''Vernal 298'' -a selection resistant to M. hapla and susceptible to D. dipsaci, ''Lahontan'' -a cultivar resistant to D. dipsaci and susceptible to M. hapla, and ''Ranger'' -a cultivar susceptible to both M. hapla and D, dipsaci. Infection with D. dipsaci depressed growth of susceptible ''Vernal 298'' and ''Ranger'' at all soil temperatures, except for ''Vernal 298'' at 16 C. Infection with M. hapla alone did not depress growth of any of the alfalfas. A combination of M. hapla and D. dipsaci resulted in a synergistic weight depression on ''Ranger'' at all soil temperatures. Inoculation of the four alfalfas with D. dipsaci 2, 4, 6, and 8 wk before inoculation with M. hapla at 16, 20, 24, and 28 C did not influence the resistance or susceptibility of ''Nev Syn XX,'' ''Lahontan,'' or ''Ranger.'' However, galling of ''Vernal 298'' by M. hapla was affected by soil temperature, plant age, and inoculation with D. dipsaci.     

Description and SEM Observations of Meloidogyne chitwoodi n. sp. (Meloidogynidae), a Root-knot Nematode on Potato in the Pacific Northwest

Meloidogyne chitwoodi n. sp. is described and illustrated from potato (Solanum tuberosum) originally collected from Quincy, Washington, USA. This new species resembles M. hapla, but its perineal pattern is basically round to oval with distinctive and broken, curled, or twisted striae around and above the anal area. The vulva is in a sunken area devoid of striae. Vesicles or vesicle-like structures are present in the median bulb of females. The larva tail, being short and blunt with a hyaline tail terminal having little or no taper to its rounded terminus, is distinctively different from M. hapla. SEM observations revealed the nature of the perineal pattern and details of the head of larvae and males, and showed the spicules to have dentate tips ventrally. Hosts for M. chitwoodi n. sp. include potato, tomato, corn, and wheat but not strawberry, pepper, or peanut. The latter three crops are excellent hosts for M. hapla. The known distribntion of this new root-knot species presently involves certain areas of Idaho, Washington, and Oregon. The common name "Columbia root-knot nematode" is proposed for M. chitwoodi n. sp.     

Immunity acquired by sheep from an experimental infection with haemonchus contortus

Adams D.B. and Beh K.J. 1981. Immunity acquired by sheep from an experimental infection with Haemonchus contortus. International Journal for Parasitology11: 381–386. A primary infection of sheep with a single dose of Haemonchus contortus larvae was traced by faecal egg counts until it had substantially declined after 55 weeks. These primed sheep were then given a sequence of two reinfections with the parasite. Comparison of faecal egg counts in primed sheep and in two separate groups of previously worm-free sheep showed that primary infection conferred significant immunity. This, however, was not sufficiently protective to prevent the development of further anaemia and faecal egg counts indicative of clinical haemonchosis. It is suggested that an adaptation in the host-parasite relationship which promotes the longevity of primary infection with H. contortus may also moderate the induction of acquired immunity.The titre of haemagglutinating antibody specific for H. contortus rose in serum during the course of primary infection, but the two reinfections did not stimulate a rise in titre. Titres of haemagglutinating antibody before reinfection did not correlate with subsequent faecal egg counts.     

Granulosis virus in the intestinal lumen of Neoaplectana carpocapsae: Retention of infectivity after treatment with formaldehyde or high pH

High pH values (>11.0) cause the dissolution of occlusion bodies of the granulosis virus (GV) of Pseudaletia unipuncta and subsequent inactivation of the virus within 24 hr. The GV is also inactivated within 48 hr by 0.04% formaldehyde. The GV is found in the intestinal lumen of infective third stage nematodes (dauer juveniles) of Neoaplectana carpocapsae when development occurs in GV-infected hosts. The GV in these dauer juveniles retains its infectivity even when the nematodes are placed into an alkaline solution with pH values of 11.1 or 12.1 or in 0.04% formaldehyde up to 336 hr. However, significant loss of infectivity of GV occurs when the nematodes are in formaldehyde but not at high pH values. The dauer juveniles are ensheathed by the second stage cuticle. This cuticle probably protects the GV in the intestinal lumen of the nematode from the high pH and formaldehyde.     

Anisakis simplex and Anisakis physeteris: physicochemical properties of larval and adult hemoglobins

To resolve the taxonomic relationship between two types of parasitic nematode larvae (Type I and II) and two species of parasitic nematode adults (Anisakis simplex and A. physeteris) of the aquatic ascarid genus Anisakis, collected in Japanese coastal water, a comparison was made of their hemoglobins' physicochemical properties. The larval hemoglobins were more similar to each other in electrophoretic pattern than to either adult, indeed there were few similarities whatsoever in these patterns of larval and adult hemoglobins. However, isoelectric points were 6.2 for the Type I larva and for A. simplex and 5.4 for the Type II larva and for A. physeteris. All samples showed identical patterns in spectrophotometric scanning. The circular dichroic spectra of the samples were also virtually identical, although slight differences were noted in the oxygenated hemoglobins; the Type II larva and A. physeteris exhibited a small positive peak at 575 nm but the Type I larva and A. simplex exhibited a much smaller peak (negative position). The sedimentation coefficients of the samples possessed essentially identical values (11.2–12.4). The molecular weights of the samples were estimated, roughly, to be in the range 33 to 43 × 10⁴ by thin-layer chromatography on Sephadex G-200. The evidence suggests that a relationship may exist between the Type I larva and A. simplex, and between the Type II larva and A. physeteris.