High-throughput amplicon sequencing of rRNA genes requires a copy number correction to accurately reflect the effects of management practices on soil nematode community structure.

Nematodes are abundant consumers in grassland soils, but more sensitive and specific methods of enumeration are needed to improve our understanding of how different nematode species affect, and are affected by, ecosystem processes. High-throughput amplicon sequencing is used to enumerate microbial and invertebrate communities at a high level of taxonomic resolution, but the method requires validation against traditional specimen-based morphological identifications. To investigate the consistency between these approaches, we enumerated nematodes from a 25-year field experiment using both morphological and molecular identification techniques in order to determine the long-term effects of annual burning and nitrogen enrichment on soil nematode communities. Family-level frequencies based on amplicon sequencing were not initially consistent with specimen-based counts, but correction for differences in rRNA gene copy number using a genetic algorithm improved quantitative accuracy. Multivariate analysis of corrected sequence-based abundances of nematode families was consistent with, but not identical to, analysis of specimen-based counts. In both cases, herbivores, fungivores and predator/omnivores generally were more abundant in burned than nonburned plots, while bacterivores generally were more abundant in nonburned or nitrogen-enriched plots. Discriminate analysis of sequence-based abundances identified putative indicator species representing each trophic group. We conclude that high-throughput amplicon sequencing can be a valuable method for characterizing nematode communities at high taxonomic resolution as long as rRNA gene copy number variation is accounted for and accurate sequence databases are available.

Relatedness of Macrophomina phaseolina isolates from tallgrass prairie, maize, soybean and sorghum.

Agricultural and wild ecosystems may interact through shared pathogens such as Macrophomina phaseolina, a generalist clonal fungus with more than 284 plant hosts that is likely to become more important under climate change scenarios of increased heat and drought stress. To evaluate the degree of subdivision in populations of M. phaseolina in Kansas agriculture and wildlands, we compared 143 isolates from maize fields adjacent to tallgrass prairie, nearby sorghum fields, widely dispersed soybean fields and isolates from eight plant species in tallgrass prairie. Isolate growth phenotypes were evaluated on a medium containing chlorate. Genetic characteristics were analysed based on amplified fragment length polymorphisms and the sequence of the rDNA-internal transcribed spacer (ITS) region. The average genetic similarity was 58% among isolates in the tallgrass prairie, 71% in the maize fields, 75% in the sorghum fields and 80% in the dispersed soybean fields. The isolates were divided into four clusters: one containing most of the isolates from maize and soybean, two others containing isolates from wild plants and sorghum, and a fourth containing a single isolate recovered from Solidago canadensis in the tallgrass prairie. Most of the sorghum isolates had the dense phenotype on media containing chlorate, while those from other hosts had either feathery or restricted phenotypes. These results suggest that the tallgrass prairie supports a more diverse population of M. phaseolina per area than do any of the crop species. Subpopulations show incomplete specialization by host. These results also suggest that inoculum produced in agriculture may influence tallgrass prairie communities, and conversely that different pathogen subpopulations in tallgrass prairie can interact there to generate 'hybrids' with novel genetic profiles and pathogenic capabilities.

Quantifying the Effects of Lance Nematode Parasitism in Creeping Bentgrass.

We compared photosynthesis and multispectral radiometry (MSR) measurements with visual quality ratings for assessment of feeding injury to creeping bentgrass caused by the lance nematode (Hoplolaimus galeatus) using artificially infested microplots and a naturally infested putting green. Nematode feeding resulted in negative visual and MSR effects on creeping bentgrass in microplots. Visual quality ratings were correlated more consistently with nematode densities than either individual MSR variables or factor models of MSR variables. Threshold estimates for H. galeatus population densities associated with unacceptable bentgrass quality in microplots varied widely by month and year. Similarly, the relationship between H. galeatus population density and turf health indicators (including MSR measurements, visual ratings, and net photosynthetic rate) varied with cultivar and management practice (irrigation frequency and mowing height) in the naturally infested putting green. Notably, negative effects of nematode feeding were not consistently associated with more stressful management practices, suggesting that stress avoidance is not a reliable deterrent to H. galeatus damage in creeping bentgrass. Damage thresholds for this nematode-host association are dynamic and should be used with caution.

Population Dynamics of the Lance Nematode (Hoplolaimus galeatus) in Creeping Bentgrass.

The effects of management practices and nematode population density on the seasonal fluctuationsin lance nematode (Hoplolaimus galeatus) populations in creeping bentgrass were studiedin a naturally infested experimental putting green and in artificially infested microplots. In general, H. galeatus populations increased from late spring through midsummer, declined in August, and increased again in the fall. Population increase in microplots was strongly density dependent, with final population densities inversely proportional to inoculum levels. Ectoparasitic populationsof H. galeatus in both studies were composed of adults and juveniles, whereas endoparasiticpopulations were almost exclusively juveniles. H. galeatus populations in the naturallyinfested site were aggregated spatially, but the aggregation was not temporally stable. Nematodepopulations were not affected by bentgrass cultivar selection or irrigation frequency.

Sentinel nematodes of land-use change and restoration in tallgrass prairie.

Changes in land use and the associated changes in land cover are recognized as the most important component of human-induced global change. Much attention has been focused on deforestation, but grasslands are among the most endangered ecosystems on Earth. The North American tallgrass prairie is a dramatic example, exhibiting a greater than 95% decline in historical area. Renewed interest in prairie conservation and restoration has highlighted the need for ecological indicators of disturbance and recovery in native systems, including the belowground component. The tallgrass prairie differs from the agricultural systems that have replaced it in having greater diversity and heterogeneity of resources, less physical soil disturbance (although other disturbances, such as fire and grazing, are prominent), and greater nitrogen limitation. Understanding the responses of nematode taxa to these characteristic differences is crucial to the development and improvement of community indices, but while knowledge of disturbance responses by individual taxa is accumulating, the level of necessary taxonomic resolution remains in question. Although nematode communities generally are better described for temperate grasslands than for other natural ecosystems, identification of sentinel taxa is further confounded by high levels of diversity, and both spatial and temporal heterogeneity.

A conceptual model of psychosomatic illness in children. Family organization and family therapy.

Linear and open systems (multiple feedback) models of psychosomatic illness in children are contrasted in terms of their implications for cause and treatment. An open systems family model is presented that describes three necessary (but not independently sufficient) conditions for the development and maintenance of severe psychosomatic problems in children: (1) a certain type of family organization that encourages somatization; (2) involvement of the child in parental conflict; and (3) physiological vulnerability. Predisposition for psychosomatic illness, symptom choice, and maintenance are discussed within this conceptual framework. We report on family therapy strategies based on this model and the results of family treatment with 48 cases of "brittle" diabetes, psychosomatic asthma, and anorexia nervosa.

Outcomes for cocaine abusers after once-a-week psychosocial therapy.

OBJECTIVE: The authors studied the efficacy of once-weekly psychotherapy, family therapy, or group therapy led by paraprofessionals among patients with cocaine use disorders. METHOD: Of subjects who sought outpatient treatment, 168 consented to participate in the study and were each randomly assigned to one of the three forms of therapy; 122 patients were interviewed 6-12 months later. Their pre- and posttreatment scores on the Addiction Severity Index were compared. RESULTS: Significant improvements were observed for the cohort as a whole, but virtually all of the improvement was restricted to the 23 subjects (19%) who were not using cocaine at follow-up. There was a strong relationship between abstinence from cocaine use and absence of addiction-related problems, especially psychiatric symptoms and family problems. CONCLUSIONS: The results of the study indicate that outpatient therapy once a week is ineffective for cocaine use disorder. The 19% abstinence rate probably represents spontaneous remission among patients with enough motivation to seek treatment, as the number of therapy sessions attended was not related to improvement. Either an intense level of outpatient contact or residential treatment followed by aftercare is probably needed, at least initially, while the patient is attempting to initiate and sustain abstinence.

Soybean Cyst Nematode Reproduction in the North Central United States.

An experiment was conducted in Heterodera glycines-infested fields in 40 north central U.S. environments (21 sites in 1994 and 19 sites in 1995) to assess reproduction of this nematode. Two resistant and two susceptible soybean cultivars from each of the maturity groups (MG) I through IV were grown at each site in 6.1 m by 4 row plots. Soil samples were collected from each plot at planting and harvest and processed at Iowa State University to determine H. glycines initial (Pi) and final (Pf) population densities as eggs per 100 cm3 of soil. Overall, reproduction (Pf/Pi) of H. glycines on susceptible cultivars in all MG was similar. Reproduction was higher on MG III and IV susceptible cultivars than on those in MG I and II. Resistant MG I and II cultivars reduced nematode population densities more consistently than those in MG III and IV. Reproduction of the nematode was similar among sites within the same maturity zone (MZ), defined as the areas of best adaptation of the corresponding MG. Nonetheless, careful monitoring of nematode population densities is necessary to assess changes that occur over time in individual fields.

GAPS between MFT supervision assumptions and common practice: suggested best practices.

This article summarizes gaps between assumptions that appear in the literature, research, and accepted standards for marital and family therapy (MFT) supervision, and the common practice of supervisors. Issues that stem from these gaps are highlighted and recommendations are made for closing them. In an effort to refine the standard of practice for MFT supervision, best practice recommendations are offered for MFT supervision.

Effect of Cropping Regime on Populations of Belonolaimus sp. and Pratylenchus scribneri in Sandy Soil.

The host efficiencies of corn, sorghum, soybean, and wheat were compared for a Kansas population of Belonolaimus sp. under greenhouse conditions. In a related field study conducted in 1989 and 1990, the responses of Belonolaimus sp. and Pratylenchus scribneri populations to eight cropping regimes were monitored at depths of 0-30 and 31-60 cm in sandy soil. With the exception of alfalfa, all crop species examined supported substantial increases in populations of both nematodes. Largest nematode population increases in the field occurred in corn plots, whereas alfalfa did not allow reproduction by either species during the 2 years of observation. Soil populations of both nematodes remained at detectable levels after 2 years of fallow. The distribution of numbers of Belonolaimus sp. between soil depths varied with sampling date, whereas populations of P. scribneri were consistently concentrated in the top 30 cm of soil.

Soybean Planting Date and Maturity Effects on Heterodera glycines and Macrophomina phaseolina in Southeastern Kansas.

Heterodera glycines reproduction and damage potential were evaluated for H. glycines-resistant and -susceptible soybean cultivars from maturity groups (MG) III, IV, and V on two planting dates in each of two years (1990-1991). Infection by H. glycines reduced yields of late-planted susceptible cultivars to a lesser degree than early planted cultivars in 1990 but not in 1991. The MG V susceptible cultivar yielded better than earlier-maturing susceptible cultivars even when yields of resistant cultivars were similar across maturity groups. Soybean yields were a function of nematode densities on roots in 1990, and nematode soil densities and root colonization by the charcoal rot fungus, Macrophomina phaseolina, in 1991. Harvest densities of H. glycines were lower for late-planted than for early-planted susceptible soybeans in 1990; however, nematode population increase was more rapid on roots of late-planted soybeans in 1991. Soybean maturity group did not have a significant effect on nematode populations in either year of the study, but colonization rates of M. phaseolina were lower for MG V cultivars than for earlier-maturing cultivars. Delayed soybean planting and cultivar maturity selection do not appear to be viable management options for H. glycines in southeastern Kansas.

Population Dynamics and Damage Potential of Belonolaimus sp. on Corn.

The population dynamics and damage potential of an undescribed species of Belonolaimus were investigated for 2 years in a naturally infested commercial corn field in southwestern Kansas and for a third year in a field microplot study. Population trends and vertical distribution of nematode life-stages were monitored and relationships between corn yields and initial or midseason nematode population densities were described using regression analyses. Nematode populations in field plots and in the top 30 cm of microplots increased following seedling emergence, then declined steadily. Numbers of adult nematodes remained relatively stable in all studies, but shifts were observed in the vertical distribution of females in microplots. Females and juveniles in microplots were concentrated in the upper 30 cm of soil 3 weeks after planting but were below normal sample depths by mid-July. Corn yields decreased linearly with increasing initial and midseason nematode population densities.

Seasonal Dynamics and Yield Relationships of Pratylenchus spp. in Corn Roots.

The seasonal distribution of Pratylenchus spp. in seminal and adventitious roots and the relationship of maize yield variables to nematode densities were examined for irrigated maize in sandy soil in 1994 and 1995. Nematode populations in seminal roots were stable or declined (P

Establishment of Heterodera glycines in Three Soil Types.

The establishment ofHeterodera glycines race 3, from soil plugs infested with population densities ranging from 0 to 10 eggs and second-stage juveniles per 10 cm(3) soil, was compared in three soils (Haynie sandy loam, Eudora silt loam, and Chase silty clay loam) that were either pasteurized or unpasteurized. Final population densities of H. glycines in soil and on soybean (Glycine max cv. Williams 82) roots were affected by soil type but not by soil pasteurization (P = 0.05). Higher numbers of H. glycines females and cysts were recovered from the sandy loam than from the silty loams after 8 weeks. The relationships between initial populations in infested soil plugs and the levels of recovery in the previously uninfested soils were described by sigmoidal Gompertz growth models. Estimated threshold levels for establishment were approximately 75% lower in the sandy loam than in the silty loams.

Interaction of Heterodera glycines and Glomus mosseae on Soybean.

The effects of the arbuscular mycorrhizal (AM) fungus Glomus mosseae on Heterodera glycines-soybean interactions were investigated in greenhouse experiments. Mycorrhizal and nonmycorrhizal soybean cultivars that were either resistant or susceptible to H. glycines were exposed to initial nematode population densities (Pi) of 0, 100, 1,000, or 10,000 eggs and infective juveniles. Soybean growth, nematode reproduction, and AM fungal colonization were determined after 35 (experiment I) and 83 (experiment II) days. Soybean shoot and root weights were reduced an average 29% across H. glycines Pi but were 36% greater overall in the presence of G. mosseae. Analyses of variance indicated that root colonization and stimulation of soybean growth by G. mosseae were inhibited at high H. glycines Pi, while the combined effects of the nematode and fungus on soybean growth were best described as additive in linear regression models. No evidence for increased nematode tolerance of mycorrhizal soybean plants was observed. Nematode population densities and reproduction were lower on a nematode-resistant soybean cultivar than on a susceptible cultivar, but reproduction was comparable on mycorrhizal and nonmycorrhizal plants. Root colonization by G. mosseae was reduced at high nematode Pi. The results suggest that nematode antagonism to the mycorrhizal symbiosis is a more likely consequence of interactions between H. glycines and AM fungi on soybean than is nematode suppression by the fungus.

Interactions of Heterodera glycines, Macrophomina phaseolina, and Mycorrhizal Fungi on Soybean in Kansas.

The impact of naturally occurring arbuscular mycorrhizal fungi on soybean growth and their interaction with Heterodera glycines were evaluated in nematode-infested and uninfested fields in Kansas. Ten soybean cultivars from Maturity Groups III-V with differential susceptibility to H. glycines were treated with the fungicide benomyl to suppress colonization by naturally occurring mycorrhizal fungi and compared with untreated control plots. In H. glycines-infested soil, susceptible cultivars exhibited 39% lower yields, 28% lower colonization by mycorrhizal fungi, and an eightfold increase in colonization by the charcoal rot fungus, Macrophomina phaseolina, compared with resistant cultivars. In the absence of the nematode, susceptible cultivars exhibited 10% lower yields than resistant cultivars, root colonization of resistant vs. susceptible soybean by mycorrhizal fungi varied with sampling date, and there were no differences in colonization by M. phaseolina between resistant and susceptible cultivars. Benomyl application resulted in 19% greater root growth and 9% higher seed yields in H. glycines-infested soil, but did not affect soybean growth and yield in the absence of the nematode. Colonization of soybean roots by mycorrhizal fungi was negatively correlated with H. glycines population densities due to nematode antagonism to the mycorrhizal fungi rather than suppression of nematode populations. Soybean yields were a function of the pathogenic effects of H. glycines and M. phaseolina, and, to a lesser degree, the stimulatory effects of mycorrhizal fungi.

The internal transcribed spacer region of belonolaimus (nemata: belonolaimidae).

Belonolaimus isolates from six U.S. states were compared by restriction endonuclease digestion of amplified first internal transcribed spacer region (ITS1) of the nuclear ribosomal genes. Seven restriction enzymes were selected for evaluation based on restriction sites inferred from the nucleotide sequence of a South Carolina Belonolaimus isolate. Amplified product size from individuals of each isolate was approximately 700 bp. All Midwestern isolates gave distinct restriction digestion patterns. Isolates identified morphologically as Belonolaimus longicaudatus from Florida, South Carolina, and Palm Springs, California, were identical for ITS1 restriction patterns. The correlation between ITS1 restriction patterns and the distribution of B. longicaudatus isolates suggest that the California isolate is a relatively recent introduction into the state.

Effects of Maturity and Determinacy in Soybean on Host-Parasite Relationships of Heterodera glycines.

The effects of soybean maturity and determinacy on the host-parasite relationships of Heterodera glycines were investigated in a field microplot study over 2 years. Determinate and indeterminate isolines of the maturity group (MG) III cultivar Williams 82 and the MG V cultivar Essex were grown in microplots artificially infested with a race 3 isolate of H. glycines at three initial population (Pi) densities (0, 300, and 3,000 eggs/100 cm(3) soil). Soybean seed yields, nematode final population (Pf) densities and reproductive index (Pf/Pi), and root colonization by Macrophomina phaseolina, the causal agent of charcoal rot, were monitored in each year. Seed yields were reduced (P

Field Response of Soybean in Maturity Groups III-V to Heterodera glycines in Kansas.

Soybean cultivars from maturity groups III-V were grown in Heterodera glycines-infested locations in northeastern and southeastern Kansas from 1991 through 1994. Yield performance and nematode reproduction were significantly (P <0.01) affected by host response to H. glycines and year, whereas effects of cultivars within host response categories and cultivar x year interactions were generally negligible. In northeastern Kansas, H. glycines-susceptible cultivars from maturity groups III-IV yielded 8% less than resistant cultivars across years, whereas in southeastern Kansas, susceptible cultivars from maturity groups IV-V yielded 38% less than resistant cultivars across years. Analyses of yield components suggested that number of pods per plant accounted for most of the differences in seed yields. Heterodera glycines reproduction rates (final population density/initial population density) averaged 0.7 and 1.3 for resistant cultivars and 8.7 and 15.9 for susceptible cultivars in northeastern and southeastern locations, respectively. Results indicated that the relative performance of resistant and susceptible cultivars can be reliably predicted based on preplant egg densities across most environments in eastern Kansas.

Density-Dependent Multiplication and Survival Rates in Heterodera glycines.

Seasonal multiplication and overwinter survival are density-dependent in Heterodera glycines. At low to moderate population densities, the nematode is capable of large population increases on susceptible soybean cultivars and high rates of oversummer or overwinter survival in the absence of a host. To improve estimates of H. glycines multiplication and survival rates, egg densities were monitored for 12 cropping sequences across 10 years. Log-linear regression analysis was used to describe and compare density-dependent relationships. Growing-season change in H. glycines egg densities was density-dependent for all crops (susceptible soybean, resistant soybean, and nonhost), with slope estimates for the density-dependent relationship greater for susceptible soybean compared with a non-host crop. Overwinter population change also was density-dependent, with similar declines in survival rates observed for all crops as population densities increased. Survival was greater following susceptible soybean compared with resistant soybean, with an intermediate rate of survival associated with non-host crops. Survival estimates greater than 100% frequently were obtained at low population densities, despite attempts to account for sampling error. Rates of growing-season multiplication and survival, when standardized for population density, declined with year of the study. Standardized overwinter survival rates were inversely related to average daily minimum temperature and monthly snow cover.