Comparisons of plant parasitic nematode populations using a resemblance equation and community ordination showed that community structure tends to be similar on dark-colored, highly productive soybean soils throughout Indiana and Illinois. On lighter-colored soils community structures differed somewhat from those of darker soils and from each other.
Ecology; Dendrogram; Similarity indices; Community ordination; Helicotylenchus pseudorobustus; Pratylenchus spp.,; Paratylenchtts projectus; Tylenchorhynchus acutus; Tylenchorhynchus martini; Xiphinema americanum
The amino acids of terminal root galls caused by Longidorus africanus on bur marigold (Bidens tripartita L.) and grapevine (Vitis vinifera L.) were studied. The galled roots of bur marigold contained 73% more cell-wall protein and 184% more free amino acids. The main changes among the free amino acids of the galled tissue were a large increase (1900%) in proline and a decrease in aspartic acid (56%) compared with the respective check tissue. Hydroxyproline decreased in the wall protein fraction from 5.6% in the healthy tissue to 3.6% in the infected tissue.
Percent of hydroxyproline in total amino acids of the wall protein fraction of grapevine roots decreased from 0.7% in the healthy tissue to 0.3% in the galled tissue, and total proteins of this fraction decreased from 9.5 mg to 4.5 rag, respectively. Total protein in the protoplasmic fraction also decreased from 3.0 mg in healthy to 1.0 mg in infected roots. No change was noticed in total proteins in the free amino acids fraction but free proline decreased 40% in the infected roots.
The relationship of these differences to the specific reactions of the hosts to nematode feeding is discussed.
Proline; Hydroxyproline; Aspartic acid; Glutamic acid
Population size and sex ratios of Pratylenchus alleni in soybeans were studied trader two different moisture regimes in Hagener loamy fine sand. Soil moisture was maintained from field capacity to 50% below field capacity in the dry regime and from field capacity to 25% above field capacity in the wet regime. The initial peak of colonization of soybeans by P. alleni was in the top 5-cm of taproot 14 days after seeding. There were more P. alleni per unit length of taproot in the dry than in the wet regime during the first 7 days, and this trend continued in the top 5-cm of the taproot for 21 days. Nematode density was greater in taproots than in fibrous roots. The ratio of males to females recovered from roots was significantly higher in the dry than in the wet regime.
Decline and disappearance of a natural population of the grasshopper Hesperotettix viridis pratensis was related to severe infection by Mermis nigrescens. In contrast the numbers of slightly infected Melanoplus bivittatus did not decrease. Uninfected M. sanguinipes, M. differentialis and M. fernur-rubrum also did not decrease. The high percentage of infection in H. viridis pratensis was related to low, wet habitat, where the grasshopper fed primarily on Solidago missouriensis; infected individuals failed to develop ovaries or mature testes. This is believed to be the first reported occurrence of a nematode parasitizing H. viridis pratensis. In juvenile M. nigrescens the unreported shape of the stoma, the stylet shape and paired oval structures in the cerebral region were photographed. Factors affecting biological control of grasshoppers by using M. nigrescens were discussed.
Melanoplus bivittatus; Melanoplus saaguinipes; Melanoplus differentialis; Melanoplus femurrubrum; Solidago missouriensis; Environmental factors; Anatomical changes; Anatomical features
Neodiplogaster tropica is redescribed from syntypes, and N. pinicola from syntypes and newly collected material. Information on the previously undescribed female tail and reproductive system is given for N. tropica, and details of the stoma, female gonad, spicules, gubernaculum, and excretory system are emphasized for N. pinicola. Lectotypes are designated for both species. The predaceous feeding of N. pinicola is described.
Taxonomy; Stoma; Excretory system; Predaceous feeding; White pine beetle
Optimum temperature for reproduction of Pratylenchus coffeae on Rough lemon, Citrus jambhiri Lush. was 29.5 C. Pratylenchus coffeae populations reached 7653 per g of root 2 months after initial inoculation with 140 nematodes. Maximum plant weight reduction was 38%; root weights were reduced by as much as 47%. Pratylenchus brachyurus significantly reduced plant and root weights but population sizes never approached those of P. coffeae. Pratylenchus coffeae survived in stored excised roots and were still infective after 4 months at temperatures ranging from 4.5 to 32 C.
Constant temperatures; Storage survival; Recovery
The rate of recovery of Pratylenchus brachyurus from cotton roots was enhanced when the tissue was incubated in solutions containing 10 ppm ethoxyethyl mercuric chloride, 50 ppm dihydrostreptomycin sulfate, 50, 100, or 1,000 ppm diisobutylphenoxethyl dimethyl benzyl ammonium chloride, or mixtures of these compounds. Incubation in 10 or 100 ppm zinc sulfate, zinc chloride, or magnesium chloride also enhanced the rate of recovery. Incubation solutions containing 1 or 1,000 ppm zinc chloride or magnesium chloride had no influence on this phenomenon, whereas, 10,000 ppm zinc sulfate, zinc chloride, or magnesium chloride retarded the rate of recovery. A t all incubation intervals during the first 21 days after the roots were removed from soil, the P. brachyurus population consisted of approximately 25% second-stage juveniles, 44% third and fourth-stage juveniles, and 31% females. At least 88% of the second-stage juveniles and 51% of the third and fourth-stage juveniles passed through a single 325-mesh sieve, whereas, 84% of the females collected were retained on a sieve of this mesh.
Gossypium hirsutum; Extraction; Incubation
Five sericea lespedeza (Lespedeza cuneata [Dumont] G. Don) breeding lines resistant to Meloidogyne incognita, M. incognita acrita, and M. hapla as seedlings in greenhouse tests and two varieties were resistant to M. incognita acrita in field experiments. Root-knot galling and larvae numbers were less for resistant entries than for the susceptible check when grown in root-knot infested field soil for three growing seasons. Forage yields were as much as 57 times greater for resistant entries than for susceptible check. Lines resistant to M. incognita acrita generally appeared more tolerant to M. javanica than the susceptible check in the field. A population predominantly M. incognita acrita built up on cotton (Gossypium hirsutum L.) and hairy vetch (Vicia villosa L.) shifted to M. javanica under sericea lespedeza.
Resistance; Forage yield
Four populations of Heterodera glycines from four different states differed considerably in numbers of adult females developed on five resistant soybean cultivars, mungbean and lespedeza. Differences were observed also in body, tail and tail terminus lengths of second-stage larvae. No attempt was made to assign these populations to recognized races, and it is suggested that race designations should be applied only to representative samples of field populations and not to selected greenhouse populations or isolates.
All motile stages of Pratylenchus coffeae infected mature and immature tissues of Citrus jambhiri (rough lemon) seedling tap roots. The nematodes fed primarily in the cortex and colonized in pockets or cavities. Intra- and intercellular migration within the cortex occurred in either direction from the point of entry. When P. coffeae invaded a root tip the meristem often was destroyed and lateral root initiation usually occurred near the destroyed root tip. Males were essential for reproduction and survived at least 2 1/2 months within root tissues, but with males alone used as inoculum, no cortical pockets were formed. On infected trees in the field P. coffeae were most numerous in C. jambhiri feeder roots.
Inoculation methods; males; mass entry; root size; biology
Caenorhabditis elegans and Panagrellus redivivus were cultured in axenic medium in microwells. The addition of selected steroids and terpenoids to the medium caused quantitative inhibition of numbers of offspring produced per well. Three out of 14 vertebrate sex hormones and analogs, and seven out of 10 insect juvenile hormones and analogs inhibited growth at 25 or 50 micrograms per ml. In addition, two insecticide synergists which mimic juvenile hormones, propyl 2-propynyl phenyl phosphonate and piperonyl butoxide, inhibited growth at 7 μg/ml. Total lipids from Panagrellus and from Nematospiroides dubius were inhibitory. Separation by silicic acid column chromatography yielded active and inactive portions. We concluded that the inhibition observed was non-specific.
Microwells; Steroids; Sesqui-terpenoids
The vertical distribution and overwintering potential of Meloidogyne graminis on field-grown Cynodon sp (var. 'Tifgreen' bermudagrass) was measured. Total populations of M. graminis were found to be lowest in March and highest in May. Larvae were most abundant in the top 5-cm of soil during periods favoring bermudagrass growth and least numerous during periods of host dormancy. Throughout the year, more t h a n 50% of the nematodes recovered each month were in roots within the top 5-cm of the soil profile. Both eggs and larvae of M. graminis overwinter in eastern Virginia.
Root-knot nematodes; Vertical distribution; Overwintering potential; Cynodon sp.
Resistance to an undescribed species of Heterodera, Osborne's cyst nematode, was compared in Nicotiana glutinosa, N. paniculata, N. plumbaginifolia and N. Iongiflora. These species were differentially resistant in greenhouse tests as shown by nematode development, the reaction of the invaded roots, and the expression of resistance in interspecific hybrids.
Sesquidiploid hybrids; Hypersensitivity
Digestive tract contents and feces of blackbirds were examined for cysts of Heterodera glycines, the soybean cyst nematode. Birds fed under laboratory conditions and trapped in naturally-infested fields were checked. Infective larvae were recovered from cysts in the excrement of birds 24 and 48 hr after they were fed cysts. Birds that were force-fed eggs and larvae discharged infective larvae in the excrement. Birds which consumed cysts mixed with feed and cysts in feed mixed with soil discharged numerous cysts containing infective larvae. Seven of 54 starlings, trapped and killed in an infested field, contained cysts in their digestive tracts.
Molting of Rotylenchus buxophilus is similar in all observed post-embryonic stages. During molting the old cuticle and cephalic framework, conus of the old stylet, vestibulum extension, linings of amphids, distal part of the linings of the excretory duct, rectum, and phasmids are shed. The new styler is formed starting from the conus, which is simultaneously formed in its entirety.
Numbers of Xiphinema bakeri increased during the first month of storage at temperatures 5-30 C in naturally-infested soil sealed in polyethylene bags. From 1 to 6 months, populations trended toward later developmental stages, and total numbers declined, especially at the higher temperatures. Similarly-packaged X. bakeri eggs, larvae and adults were killed by -18 C for 48 hr or -34 C for 12 hr.
Two years of giant star grass, Cynodon nlemluensis var. nlemfuensis, in a field plot markedly reduced the incidence of the root-knot nematodes. Tomato planted following the grass showed very little or no root galling and the yield was thrice that of tomato planted on an adjacent field plot previously cropped to tomato. Replicated greenhouse experiments indicated that six varieties of Cynodon were resistant to root-knot nematode but it took up to 6 months of grass growth to appreciably lower the nematode population. The nematodes were eliminated from the soil by all the six grass varieties after 18 months.
Cynodon nlemfuensis; Giant star grass; nematode control
Electron microscopy of the photoreceptors in the marine nematode, Deontostoma californicum, revealed numerous lamellated inclusions in the Schwann cells ensheathing the lateral cephalic nerves. Immediately after the axons from the modified bipolar neurons of the photoreceptors enter the lateral nerves, these spherical-to-oval lamellated bodies are observed in the surrounding Schwann cell cytoplasm. These previously undescribed Schwann cell inclusions, approximately 500 nm long and 320 nm in diameter, are lamellated and characterized by the presence of an electron-dense stalk-like process, 80-280 nm long. The lamellated inclusions are bound by a single limiting membrane, 6-7 nm thick, which shows occasional interruptions. The internal structure of the inclusions is characterized by the presence of electron-dense lamellae or bands, 11-16 nm thick, which assume various complex patterns ranging from arrays of parallel linear densities to a reticulate appearance. In addition, the nematode Schwann cell cytoplasm contains the usual organelles, gliosome- and lysosome-like inclusions. Their relationship with lipofuscin pigments is briefly discussed.
Pyruvic acid, lactic acid and several tricarboxylic acid cycle acids were extracted from Ditylenchus triformis and Turbatrix aceti and identified. Fumaric acid was predominant in both nematodes. Small amounts o f malic and α-ketoglutaric acids and intermediate quantities o f lactic, citric, succinic, and pyruvic acids occurred in D. triformis. In T. aceti citric, lactic, and α-ketoglutaric acids were less abundant than succinic, malic and pyruvic acids. Only traces of aconitic and oxalacetic acids occurred in both nematodes. All the organic acids detected accounted for only about one per cent of the dry weight of nematodes o f the two species.
Tricarboxylic acid cycle acids
A larval population of the white-fringed beetle, Graphognathus peregrinus (Buchanan), in a Louisiana grassland field was reduced 38% by Neoaplectana dutkyi Jackson ('DD-136' nematode) applied at 430,000 nematodes per m². In Mississippi an artificial population was reduced 50% by the nematode applied at 538,000 per m².
Biological control; Insect-parasitic nematodes
'Amsoy' soybeans were grown for 2 months in nonsterilized Jackson silt loam amended to pH 4.0, 6.0, and 8.0. Nematodes were extracted biweekly from soil and roots. The greatest numbers of Pratylenchus alleni colonized soybean roots at pH 6.0. Hoplolaimus galeatus and members of the Tylenchinae-Psilenchinae survived best at pH 6.0, while numbers o f the Dorylaimoidea were greatest at both pH 6.0 and 8.0. The non-stylet nematodes were recovered in greater numbers from pH 8.0 soil. Potassium, manganese, and phenols were highest in soybean plants grown in pH 4.0 soil, the pH at which there were the fewest nematodes. A thicker suberized outer layer o f root tissue occurred in plants grown at pH 4.0.
Pratylenchus alleni; pH; Soybeans