A new apparatus to release eggs from cysts of soybean cyst nematode (Heterodera glycines) is described and its efficiency evaluated. A rubber stopper was mounted on a bolt, and cysts were ground against a 60-mesh screen. Eggs and second-stage juveniles were washed into a series of screens nested underneath the apparatus. This method was fast and efficient, and had no ill effect on prepared inoculum.
apparatus; chemical; eggs; extraction; Heterodera glycines; inoculation; mechanical; method; nematode; soybean; soybean cyst nematode
Globodera millefolii and G. artemisiae are interesting because their type localities (Estonia and Russia, respectively) are geographically distant from those of the potato cyst nematodes and other Globodera species that seem to have originated in the Western world, and because the type host for each is a member of Compositae rather than Solanaceae. Sequence data for ITS1, ITS2, and 5.8S ribosomal DNA (ITS rDNA) for G. millefolii and G. artemisiae were nearly identical to sequence data for Cactodera salina from the rhizosphere of the estuary plant Salicornia bigelovii in Sonora, Mexico. The ITS rDNA sequences of these three species were all about 94% similar to those of two other Cactodera species for which ITS rDNA data were obtained. Phylogenetic analysis indicated that, based on the ITS rDNA data, G. millefolii and G. artemisiae are more closely related phylogenetically to the Cactodera species than to other nominal Globodera species. The molecular data further suggest that the genus Cactodera may comprise two or more morphologically similar but separate groups.
Cactodera; Cactodera salina; Globodera; Globodera artemisiae; Globodera millefolii; ITS1; ITS2; nematode; phylogenetic analysis; ribosomal DNA; rDNA; 5.8S gene
The number of resistance genes in soybean to soybean cyst nematode (SCN) Heterodera glycines was estimated using progeny from a cross of 'Williams 82' x 'Hartwig' (derived from 'Forrest'³ x PI 437.654) screened with a fourth-generation inbred nematode line derived from a race 3 field population of SCN. Numbers of females developing on roots of inoculated seedlings were assigned to phenotype cells (resistant, susceptible, or segregating) using Ward's minimum variance cluster analysis. The ratio obtained from screening 220 F₃ soybean families was not significantly different from a 1:8:7 (resistant:segregating:susceptible) ratio, suggesting a two-gene system for resistance. The ratio obtained from screening 183 F₂ plants was not significantly different from a 3:13 (resistant:susceptible) ratio, indicating both a dominant (Rhg) and a recessive (rhg) resistance gene.
Glycine max; Hartwig; Heterodera glycines; PI 437.654; resistance soybean; soybean cyst nematode; soybean resistance gene
Ribosomal DNA (rDNA) sequence data were compared for five species of Globodera, including G. rostochiensis, G. pallida, G. virginiae, and two undescribed Globodera isolates from Mexico collected from weed species and maintained on Solanum dulcamara. The rDNA comparisons included both internal transcribed spacers (ITS1 and ITS2), the 5.8S rRNA gene, and small portions of the 3' end of the 18S gene and the 5' end of the 28S gene. Phylogenetic analysis of the rDNA sequence data indicated that the two potato cyst nematodes, G. pallida and especially G. rostochiensis, are closely related to the Mexican isolates, whereas G. virginiae is relatively dissimilar to the others and more distantly related. The data are consistent with the thesis that Mexico is the center of origin for the potato cyst nematodes.
Globodera; G. rostochiensis; G. pallida; G. virginiae; G. tabacum; nematode; ribosomal DNA; rDNA ITS1 and ITS2; 5.8S rRNA gene
Six geographic isolates of Heterodera avenae, including two isolates each from Sweden, Australia, and the United States, were compared on the basis of 2-D PAGE protein patterns and the complete DNA sequence for the two internal transcribed ribosomal DNA spacers (rDNA ITS1 and ITS2) and the 5.8S rRNA gene. The protein pattern data and rDNA ITS sequence data both indicated that the Swedish Gotland strain of H. avenae differed markedly from the rest of the isolates. Protein patterns for the Australia isolates differed more from a Swedish strict H. avenae isolate and isolates from Oregon and Idaho, than the two U.S. isolates and the Swedish strict H. avenae isolate differed from each other. Except for the Gotland strain isolate, the rDNA ITS sequences were highly conserved among all of the H. avenae isolates, just as we earlier found them to be conserved among species of the schachtii group of Heterodera.
Heterodera avenae; nematode; 2-D PAGE; protein pattern; ribosomal DNA; rDNA ITS1 and ITS2; 5.8S rRNA gene
Ecologists are concerned with population dynamics of organisms and with the spatial patterns of single or multiple populations. The goal of the ecologist is usually to explain the observed patterns in terms of processes. Field samples of nematodes from different habitats may contain similar but not identical specimens of a nominal taxon, and the systematist can help the ecologist decide whether the specimens are ecophenotypes of a single taxon or represent distinct species. A correct decision may be important or trivial, depending on the parameters and goals of the ecological study. When a precise identification is crucial to the success of the study, new biochemical methodologies of systematists may provide rapid and accurate diagnoses. Systematists can provide additional help in the assignment of taxa to trophic groups. For clarifying host-parasite associations, often a goal in ecological investigations, modern analytical methods of systematists can facilitate the ordering of systematic relationships.
coevolution; nematode species; taxa; trophic group
Data from two-dimensional protein patterns for nine dorylaimid isolates were analyzed using PAUP, a computer program for inferring phylogenies under the principle of maximum parsimony. With a variety of available options, including branch swapping and rooting, essentially the same tree was obtained. When isolates of the genus Labronema were analyzed alone, all trees obtained had the same topology, although tree length varied considerably, depending on whether a hypothetical ancestral taxon was included.
Labronema; Eudorylaimus; Aporcelaimellus; 2-D PAGE; phylogenetic analysis; PAUP; Dorylaimida
Two-dimensional polyacrylamide gel electrophoretic patterns of proteins for two isolates of Labronema from Indiana were nearly identical to the pattern for L. vulvapapillatum from Europe. The pattern for a nominal isolate of L. pacificum from Florida was very different from the patterns of nominal L. pacificum isolates from Hawaii and Fiji (which had patterns very similar to each other). Patterns for four other isolates (in Eudorylaimus and Aporcelaimellus) were different from the Labronema patterns and from each other, although some constellations of protein spots were shared among all the isolates. The study demonstrates the utility of 2-D PAGE for clarifying taxonomic problems that cannot be resolved using classical morphological data alone.
two-dimensional gel electrophoresis; 2-D PAGE protein patterns; Labronema; Aporcelaimellus; Eudorylaimus; Nematoda: Dorylaimida; systematics; Jaccard analysis; similarity coefficient
Four of five geographical isolates of Heterodera glycines from Indiana classified as Race 3 using standard differentials showed many differences when classified using another group of differentials comprised of five soybean breeding lines and cultivars. Two isolates from northern Indiana produced cysts on more of the differentials tested than did three isolates from southern Indiana, suggesting that potential resistant lines should be tested on a range of H. glycines populations originating from the areas for which cultivars are being developed.
soybean cyst nematode; Glycine max; pathogenicity; Heterodera glycines; soybean
Protein patterns obtained by two-dimensional polyacrylamide gel electrophoresis for three isolates of Heterodera glycines from southern Indiana appear qualitatively similar and have higher pairwise Jaccard similarity coefficients with each other than with isolates from northern Indiana. Three isolates from three northern counties share proteins not present in the southern isolates, but as a group the northern isolates are less similar to each other than are the southern Indiana isolates.
soybean cyst nematode; polyacrylamide gel electrophoresis
Although much morphometric overlap occurs among five geographical isolates of Heterodera glycines in Indiana, significant differences in means exist among the isolates for various comparisons of second-stage juveniles. By using combinations of means, most of the isolates can be distinguished from the rest: e.g., the Vanderburgh County isolate (southern Indiana) has the longest esophagus, tail, and tail terminus; the Vigo County isolate (also from the south) has the shortest esophagus; the White County isolate (northern Indiana) has the shortest tail and tail terminus and the greatest total length; the Benton County isolate (north) is the shortest. Morphological similarities and differences do not appear to be coordinated with reproductive behavioral patterns we observed in the northern versus the southern isolates.
soybean cyst nematode; Glycine max; soybean; Heterodera glycines; Indiana; morphology; races; geographical isolate
Two-dimensional polyacrylamide gel electrophoretic protein patterns of H. glycines from southern Indiana (Posey County) and northern Indiana (Pulaski County) were largely similar, but many differences existed. The pattern of the Posey isolate was similar to patterns from isolates collected in other areas of the United States. Unique dense protein spots in the pattern of an isolate from Hokkaido, Japan, distinguished it from patterns of six U.S. isolates.
soybean cyst nematode; two-dimensional gel electrophoresis; soybean
Examination of dispersional characteristics of Pratylenchus scribneri and Hoplolaimus galeatus indicated that there were patches within soybean fields in which both survival and reproduction wexe enhanced in spite of apparent homogeneity of soil type and topography. Treatment with carbofuran reduced the patchiness (or increased the dispersion) for H. galeatus while it had the opposite effect for P. scribneri. P. scribneri was less highly dispersed in conventional tillage plots than in the zero tillage plots. Populations from quadrats contained entirely within the patches could be described by the normal distribution (in the case of P. scribneri) or by the Poisson distribution (in the case of H. galeatus), while populations from quadrats contained entirely outside the patches could be described by the Poisson distribution for both nematodes. None of the distributions tested (Poisson, normal, negative binomial, Neyman's) gave an adequate fit when populations from both inside and outside the patches were considered together. In all instances, log₁₀ and ln transformations reduced the goodness of fit of the data to all of the distributions tested. Even with logarithmic transformations, parametric statistics were not appropriate for analysis of data in most instances.
nematode frequency; population ecology; index of dispersion; plot size selection; data transformation
Of eight corn inbreds tested in the greenhouse and field, three (H60, H95, and H84) supported lower populations of Pratylenchus hexincisus than other inbreds included in this study. No apparent differences existed among inbreds in nematode invasion or development in the roots, or in population structure. Differences in population were therefore attributed to differential reproduction.
lesion nematode; corn nematode; screening
Leptonchoid species found in soil samples taken in lowland and mid-elevation seasonal forests at four locations in Panama were as follows: Sclerostylus karri n. gen., n. sp., Basirotyleptus saccatus n. sp., B. nemoralis, B. acus, B. penetrans, Doryllium neotropicum n. sp., D. minor, Tyleptus gymnochilus, Gerthus jamesi, Dorylaimoides micoletzkyi, and Tylencholaimellus macrophallus. The discoveries corroborate our earlier suggestion of a Gondwanian origin for Tyleptus and Basirotyleptus and provide data for additional biogeographical study.
Basirotyleptus; Doryllium; Tyleptus; Gerthus; Dorylaimoides; Tylencholaimellus; nematode taxonomy; Gondwanaland
Nematode communities of 18 Indiana mixed hardwood stands were comprised of an average of 23% tylenchid species, 31% dorylaimid species, and 46% species of six other orders. Based on total numbers of individuals present the stands averaged 42% tylenchids, 20% dorylaimids, and 38% individuals of other orders. Ordination of the sites using data only for tylenchid species gave an even distribution of sites, indicating little effect of site disturbances on tylenchid populations. By contrast an ordination using data for dorylaimid species showed a high degree ofd issimilarity between reference sites indicating that disturbances at some sites had drastically affected the dorylaimid fauna. An ordination utilizing biomass of all species present was very similar to the ordination based on data for dorylaimid species only.
Indiana hardwood stands; Tylenchida; Dorylaimida; Rhabditida; Teratocephalida; Araeolaimida; Monhysterida; Chromadorida; Enoplida
Intersite relationships among nematode communities of 18 Indiana mixed hardwood stands of varying composition, soils, physiography and past management practices were determined by community ordination techniques. All sites were sampled in April, July and October of 1968 and 1969, and ordinations were based on the number of individuals of each nematode species at each site at each sampling period. The resulting groupings correlated well with groupings based on forest types and successional stages of the tree communities at the sites, and also with groupings based on well-defined soil types. Results were similar to those obtained previously with a resemblance equation which used qualitative data only; but the present study provided more information on species associations and relationships and ecological distance between sites.
Indiana hardwood stands
Associations among nematode communities were studied in 18 Indiana mixed-hardwood stands of varying composition, soils, physiography, and past management practices. All sites were sampled in April, July, and October of 1968 and 1969. A total of 175 species representing eight orders were found, with 18 species occurring in all 18 sites, and approximately half the total species occurring in more than 50% of the sites. Taxonomic similarity, based on nematode species composition, was determined for the woodlots by means of a resemblance equation. Woodlots containing similar nematode species also showed similarities in dominant tree species and in soil types. Sites that had undergone major disturbances were the most dissimilar.
Indiana hardwood stands; resemblance equation
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 effect of soil temperatures 7-25 C upon injury to seedling onions by Pratylenchus penetrans was investigated. At 7-13 C < 100 nematodes/g of root caused significant reduction in onion root weights by the fifth week. More than 400 nematodes/g were required to produce comparable injury at 16-25 C.
Pratylenchus penetrans; Pathogenicity; Onion seedlings; Soil Temperature