RESUMEN
The soybean cyst nematode Heterodera glycines (SCN) is of major economic importance and widely distributed throughout soybean production regions of the United States where different maturity groups with the same sources of SCN resistance are grown. The objective of this study was to assess SCN-resistant and -susceptible soybean yield responses in infested soils across the north-central region. In 1994 and 1995, eight SCN-resistant and eight SCN-susceptible public soybean cultivars representing maturity groups (MG) I to IV were planted in 63 fields, either infested or noninfested, in 10 states in the north-central United States. Soil samples were taken to determine initial SCN population density and race, and soil classification. Data were grouped for analysis by adaptation based on MG zones. Soybean yields were 658 to 3,840 kg/ha across the sites. Soybean cyst nematode-resistant cultivars yielded better at SCN-infested sites but lost this superiority to susceptible soybean cultivars at noninfested sites. Interactions were observed among initial SCN population density, cultivar, and location. This study showed that no region-wide predictive equations could be developed for yield loss based on initial nematode populations in the soil and that yield loss due to SCN in our region was greatly confounded by other stress factors, which included temperature and moisture extremes.
RESUMEN
The high degree of parasitic variability in Heterodera glycines and its distribution in a wide range of soybean production systems present multiple challenges for management, which necessitate increased understanding of the biology of H. glycines. Soil amendments are being considered either as stand-alone and/or as part of integrated management approaches. A recycled municipal biosolid with nutrition supplement and liming qualities, N-Viro Soil (NVS) has potential as a multi-purpose soil amendment. In three greenhouse experiments, the effects of 0, 1.0 or 4.0 g NVS/100 cm(3) of sandy loam soil on three H. glycines populations (GN1, GN2 and GN3) were investigated on soybean grown for 557 +/- 68 degree-days (base 10 degrees C). The response of the three H. glycines populations to NVS treatment varied by experiment. The overall numbers of preadult stages and cysts generally decreased with increasing levels of NVS in all experiments, and the high rate was more effective than the low rate in suppressing H. glycines numbers. This suggests that the high NVS treatment can affect the three populations in the experimental soil type under controlled conditions. Field studies to determine efficacy of the soil amendment in a wide range of environments should be initiated.
RESUMEN
A genetic linkage map of the soybean cyst nematode (SCN) Heterodera glycines was constructed using a population of F2 individuals obtained from matings between two highly inbred SCN lines, TN16 and TN20. The AFLP fingerprinting technique was used to genotype 63 F2 progeny with two restriction enzyme combinations (EcoRI/MseI and PstI/TaqI) and 38 primer combinations. The same F2 population was also genotyped for Hg-cm-1 (H. glycines chorismate mutase-1), a putative virulence gene, using real-time quantitative PCR. Some of the markers were found to be distributed non-randomly. Even so, of the 230 markers analyzed, 131 could be mapped onto ten linkage groups at a minimum LOD of 3.0, for a total map distance of 539 cM. The Hg-cm-1 locus mapped to linkage group III together with 16 other markers. The size of the H. glycines genome was estimated to be in the range of 630-743 cM, indicating that the current map represents 73-86% of the genome, with a marker density of one per 4.5 cM, and a physical/genetic distance ratio of between 124 kb/cM and 147 kb/cM. This genetic map will be of great assistance in mapping H. glycines markers to genes of interest, such as nematode virulence genes and genes that control aspects of nematode parasitism.
Asunto(s)
Ligamiento Genético , Glycine max/parasitología , Nematodos/genética , Animales , Mapeo Cromosómico , Marcadores Genéticos , Genotipo , Reacción en Cadena de la PolimerasaRESUMEN
For many years the taxonomy of the genus Pasteuria has been marred with confusion because the bacterium could not be cultured in vitro and, therefore, descriptions were based solely on morphological, developmental, and pathological characteristics. The current study sought to devise a simple method for PCR-amplification, cloning, and sequencing of Pasteuria 16S rDNA from small numbers of endospores, with no need for prior DNA purification. Results show that DNA extracts from plain glass bead-beating of crude suspensions containing 10,000 endospores at 0.2 x 10 endospores ml(-1) were sufficient for PCR-amplification of Pasteuria 16S rDNA, when used in conjunction with specific primers. These results imply that for P. penetrans and P. nishizawae only one parasitized female of Meloidogyne spp. and Heterodera glycines, respectively, should be sufficient, and as few as eight cadavers of Belonolaimus longicaudatus with an average number of 1,250 endospores of "Candidatus Pasteuria usgae" are needed for PCR-amplification of Pasteuria 16S rDNA. The method described in this paper should facilitate the sequencing of the 16S rDNA of the many Pasteuria isolates that have been reported on nematodes and, consequently, expedite the classification of those isolates through comparative sequence analysis.
RESUMEN
Light and transmission electron microscopy were used to investigate the life cycle and ultrastructure of an undescribed isolate of Pasteuria that parasitizes the soybean cyst nematode, Heterodera glycines. Studies also were conducted to determine the host specificity of Pasteuria. The endospores that attached to the cuticle of second-stage juveniles (J2) of H. glycines in soil did not germinate until the encumbered nematodes invaded soybean roots. Thereafter, the bacterium developed and completed its life cycle only in females. The stages of endosporogenesis were typical of Pasteuria spp. The mature endospore, like that of P. nishizawae, the only other Pasteuria known to infect H. glycines, produces an epicortical layer that completely surrounds the cortex, an outer spore coat that tapers progressively from the top to the base of the central body, and a double basal adhesion layer. However, subtle differences exist between the Pasteuria from North America and P. nishizawae with regard to size of the central body, nature and function of the mesosomes observed in the earlier stages of endosporogenesis, and appearance of the fibers lining the basal adhesion layer and the exosporium of the mature endospore. Endospores of the North American Pasteuria attached to J2 of H. schachtii, H. trifolii, and H. lespedezae but not to Meloidogyne arenaria race 1, Tylenchorhynchus nudus, and Labronema sp. Results from this study indicate that the North American Pasteuria is more similar to P. nishizawae than to any other known member of the genus. Additional evidence from comparative analysis of 16S rDNA sequences is needed to clarify whether these two Pasteuria belong to the same species.
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Field experiments were conducted at locations in northern and southern Illinois, central Iowa, and central Missouri from 1997 to 1999 to investigate the effects of Heterodera glycines on soybean growth, development, and yield. A wide range of infestation levels was present at all locations. Two locally adapted cultivars, one resistant to H. glycines, were grown at each location. Cultivars were planted in alternating four-row strips with 76 cm between rows. For each cultivar, 20 1-m-long single-row plots were sampled every 2 weeks starting 4 weeks after planting. Infection by H. glycines reduced plant height and leaf and stem weight on the resistant cultivars in the first 12 weeks after planting, and delayed pod and seed development 12 to 14 weeks after planting. Biomass accumulation was not reduced on the susceptible cultivars until 10 weeks after planting; reduction in pod and seed development occurred throughout the reproductive stages. Susceptible cultivars produced significantly lower yields than resistant cultivars, but the yield reductions were not accompanied by visually detectable symptoms.
RESUMEN
Several abiotic and biotic stresses can affect soybean in a growing season. Heterodera glycines, soybean cyst nematode, reduces yield of soybean more than any other pathogen in the United States. Field and greenhouse studies were conducted to determine whether preemergence and postemergence herbicides modified the reproduction of H. glycines, and to determine the effects of possible interactive stresses caused by herbicides and H. glycines on soybean growth and yield. Heterodera glycines reproduction factor (Rf) generally was less on resistant than susceptible cultivars, resulting in a yield advantage for resistant cultivars. The yield advantage of resistant cultivars was due to more pods per plant on resistant than susceptible cultivars. Pendimethalin reduced H. glycines Rf on the susceptible cultivars in 1998 at Champaign, Illinois, and in greenhouse studies reduced dry root weight of H. glycines-resistant and susceptible cultivars, therefore reducing Rf on the susceptible cultivars. The interactive stresses from acifluorfen or imazethapyr and H. glycines reduced the dry shoot weight of the resistant cultivar Jack in a greenhouse study. Herbicides did not affect resistant cultivars' ability to suppress H. glycines Rf; therefore, growers planting resistant cultivars should make herbicide decisions based on weeds present and cultivar tolerance to the herbicide.
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The effects of no-tillage (NT), conventional tillage (CT), and crop rotation on soybean yield and population dynamics of Heterodera glycines were compared during a 7-year study in a silty clay loam soil with 6% organic matter. Either H. glycines-resistant 'Linford' soybean or susceptible 'Williams 82' soybean was rotated with corn and grown on 76-cm-wide rows in both tillage systems. Soybean was planted in 1994, 1996, 1998, 1999, and 2000. Yield of Linford was significantly greater than Williams 82 in all years. Soybean yield was affected by tillage in 1999 and 2000. No-tillage production tended to support more reproduction (R = number of eggs at harvest/number of eggs at planting) on both cultivars. The largest R for Williams 82 were in 1998: 58.35 for NT plots and 11.78 for CT plots. For Linford, the largest R were 12.09 for NT plots in 1996, and 3.71 for CT in 1999. When corn was planted, R decreased more in NT. When soybean was planted in years subsequent to 1994, numbers of eggs at harvest (Pf) were greater for Williams 82 NT than for Williams 82 CT or Linford in both tillage systems; however, crop rotation with corn negated these population increases. The soil became suppressive to H. glycines in 1999 and was suppressive in 2000. After the 3 years of continuous soybean, Pf per 250 cm[sup3] soil were 2,870 for Williams 82 NT, 791 for Williams 82 CT, 544 for Linford NT, and 990 for Linford CT in 2000, compared with Pf of 13,100 for Williams 82 NT, 15,000 for Williams CT, 2,360 for Linford NT, and 2,050 for Linford CT in 1994. Describing population dynamics solely on the basis of R was not adequate, but also required independent examination of initial populations following overwintering and Pf after the growing season. Planting soybean either NT or CT in rotation with corn did not result in long-term increases in numbers of H. glycines eggs.
RESUMEN
Heterodera glycines, the soybean cyst nematode, is a major yield-limiting pathogen in most soybean production areas worldwide. Field populations of H. glycines exhibit diversity in their ability to develop on resistant soybean cultivars. Since 1970, this diversity has been characterized by a bioassay used to assign a race classification to a population. The value of the race scheme is reflected in the number and quality of resistant soybean cultivars that have been developed and released by soybean breeders and nematologists working in concert. However, the race scheme also has been misapplied as a means of studying H. glycines genotypes, in part due to the use of the term "race." For fungal and bacterial pathogen species, "race" can theoretically be applied to individuals of a population, thus allowing inference of individual genotypes. Application of a race designation to an individual egg or second-stage juvenile (J2) of H. glycines is not possible because a single J2 cannot be tested on multiple hosts. For other nematode species, "race" is defined by host ranges involving different plant species, whereas the H. glycines race test involves a set of lines of the same plant species. Nonetheless, because H. glycines populations vary in genetic diversity, and this variation has implications for management strategies, a mechanism is needed for documenting and discussing population differences. The HG Type scheme described herein avoids the implication of genetic uniformity or predictability in contrast to the way the race scheme has been used.
RESUMEN
A 1341 bp sequence of the 16S rDNA of an undescribed species of Pasteuria that parasitizes the soybean cyst nematode, Heterodera glycines, was determined and then compared with a homologous sequence of Pasteuria ramosa, a parasite of cladoceran water fleas of the family Daphnidae. The two Pasteuria sequences, which diverged from each other by a dissimilarity index of 7%, also were compared with the 16S rDNA sequences of 30 other bacterial species to determine the phylogenetic position of the genus Pasteuria among the Gram-positive eubacteria. Phylogenetic analyses using maximum-likelihood, maximum-parsimony and neighbour-joining methods showed that the Heterodera glycines-infecting Pasteuria and its sister species, P. ramosa, form a distinct line of descent within the Alicyclobacillus group of the Bacillaceae. These results are consistent with the view that the genus Pasteuria is a deeply rooted member of the Clostridium-Bacillus-Streptococcus branch of the Gram-positive eubacteria, neither related to the actinomycetes nor closely related to true endospore-forming bacteria.
Asunto(s)
Glycine max/parasitología , Bacterias Grampositivas Formadoras de Endosporas/clasificación , Bacterias Grampositivas Formadoras de Endosporas/genética , Filogenia , ARN Ribosómico 16S/genética , Tylenchoidea/microbiología , Animales , ADN Bacteriano/química , ADN Bacteriano/genética , ADN Ribosómico/química , ADN Ribosómico/genética , Femenino , Bacterias Grampositivas Formadoras de Endosporas/fisiología , Datos de Secuencia Molecular , América del Norte , Enfermedades de las Plantas/parasitología , Reacción en Cadena de la Polimerasa , Análisis de Secuencia de ADN , Esporas Bacterianas/fisiología , Tylenchoidea/aislamiento & purificación , Tylenchoidea/fisiologíaRESUMEN
Cotyledon explants of 10 soybean [Glycine max (L.) Merr.] cultivars were inoculated with Agrobacterium rhizogenes strain K599 with and without binary vectors pBI121 or pBINm-gfp5-ER possessing both neomycin phosphotransferase II (nptII) and beta-glucuronidase (gus) or nptII and green fluorescent protein (gfp) genes, respectively. Hairy roots were produced from the wounded surface of 54-95% of the cotyledon explants on MXB selective medium containing 200 microg ml(-1) kanamycin and 500 microg ml(-1) carbenicillin. Putative individual transformed hairy roots were identified by cucumopine analysis and were screened for transgene incorporation using polymerase chain reaction. All of the roots tested were found to be co-transformed with T-DNA from the Ri-plasmid and the transgene from the binary vectors. Southern blot analysis confirmed the presence of the 35S-gfp5 gene in the plant genomes. Transgene expression was also confirmed by histochemical GUS assay and Western blot analysis for the GFP. Attempts to induce shoot formation from the hairy roots failed. Infection of hairy roots of the soybean cyst nematode (Heterodera glycines Ichinohe)-susceptible cultivar, Williams 82, with eggs of H. glycines race 1, resulted in the development of mature cysts about 4-5 weeks after inoculation. Thus the soybean cyst nematode could complete its entire life cycle in transformed soybean hairy-root cultures expressing GFP. This system should be ideal for testing genes that might impart resistance to soybean cyst nematode.
Asunto(s)
Glycine max/parasitología , Nematodos/crecimiento & desarrollo , Raíces de Plantas/parasitología , Animales , Cotiledón/microbiología , Cotiledón/parasitología , ADN Bacteriano/genética , Femenino , Fluorescencia , Glucuronidasa/genética , Glucuronidasa/metabolismo , Proteínas Fluorescentes Verdes , Imidazoles/análisis , Kanamicina/farmacología , Resistencia a la Kanamicina/genética , Proteínas Luminiscentes/genética , Proteínas Luminiscentes/metabolismo , Nematodos/aislamiento & purificación , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/microbiología , Plantas Modificadas Genéticamente , Reacción en Cadena de la Polimerasa , Piridinas/análisis , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Rhizobium/genética , Rhizobium/crecimiento & desarrollo , Glycine max/crecimiento & desarrollo , Glycine max/microbiologíaRESUMEN
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.
RESUMEN
A two-year soil sampling study was conducted on four microplots naturally infested with Heterodera glycines and an undescfibed species of Pasteuria. The objectives of the study were to investigate the population dynamics of both organisms and to assess the potential of Pasteuria sp. as a biological control agent of H. glycines. Seasonal fluctuations were observed in numbers of cysts, eggs per cyst, second-stage juveniles (J2) of H. glycines, number of Pasteuria endospores attached per J2, and percentages of endospore-encumbered J2. Percentages of endospore-encumbered J2, Y, increased with the mean numbers of endospores per J2, X, according to the equation Y = 87.0(1 - e(-0.53X)). In contrast, numbers of J2 per 250 cm(3) soil, Y, decreased with the numbers of endospores per J2, X, according to the exponential decay model Y= 67.4 + 220.1e(-1.2X). The equilibrium J2 density (67.4 +/- 3.3) derived from this function was consistent with the predictions of the Lotka-Volterra model of population dynamics based on the equation 0.0195ln(y) - 0.000336y = 0.000049x - 0.00285ln(x) + 0.06589, where x and y represent the biweekly means of J2 densities and the percentages of endospore-encumbered J2, respectively. In all cases, predicted equilibrium densities of J2 were below the damage threshold reported from field studies. These results indicate that, given sufficient time following introduction into a field, Pasteuria may increase to levels that would be effective as one component in an integrated pest management proglmn to control H. glycines.
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Individual females from 19 populations of Heterodera glycines from China, Japan, and the United States were analyzed for esterase allozyme polymorphism. Eight esterase electrophoretic phenotypes were resolved. Four putative loci, est-1, est-2, est-3, and est-4, were identified, having one, one, two, and one allele, respectively. The four loci expressed six genotypes in the four Chinese populations. Loci est-2, est-3, and est-4 were identified in five Japanese populations and expressed five genotypes, whereas only loci est-2 and est-3 were identified in 10 populations from the United States and expressed four genotypes. Putative alleles at each locus were defined as characters for data analysis. Phylogenetic analysis using parsimony (PAUP) was utilized to determine relationships among the 19 populations. More loci and alleles in populations from China and phylogenetic similarities among populations from Japan and the United States are consistent with a founder effect resulting from dissemination of progenitor H. glycines from China to Japan and subsequent introductions of founder populations from Japan to the United States.
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Sudden death syndrome (SDS) is an important soybean disease that potentially can be controlled by host plant resistance. In this study, over 800 soybean plant introductions (PIs), lines, and cultivars were screened for resistance to Fusarium solani. Of 728 PIs from China, PI 567.374 had mean foliar SDS severities significantly (P = 0.05) lower than PI 520.733 (resistant check) in both growth-chamber and greenhouse tests. In addition, PIs 567.315, 567.441C, 567.650B, and 567.664 had mean SDS severity ratings significantly (P = 0.05) lower than PI 520.733 in a growth-chamber test. Of 16 soybean cyst nematode-resistant entries tested, 5 had values lower than the resistant check, PI 520.733, with cv. Hartwig significantly lower in the first trial. In trial two, no entries were lower than the resistant check, although cvs. Bell and Hartwig were not significantly different from PI 520.733. In another experiment, few soybean cultivars or experimental lines had SDS severity ratings lower than PI 520.733 in any one of three trials. Some of the newly acquired PIs from China that exhibited low foliar SDS severity ratings may provide the sources of resistance needed to develop new SDS-resistant soybean breeding lines and cultivars.
RESUMEN
An 11-year field study was initiated in 1979 to monitor population development of Heterodera glycines. Fifty cysts of a race 5 population were introduced into plots in a field with no history of soybean production and that had been in sod for 20 years. Soybean cultivars either susceptible or resistant to H. glycines were grown either in monoculture or rotated with maize in a 2-year rotation. During the first 5 years, resistant cultivars with the Peking source of resistance were planted. After year 5, monocuhure of Peking resistance resulted in 18 cysts/250 cm(3) of soil, whereas populations resulting from the continuous cropping of susceptible soybean resulted in 45 cysts/250 cm(3). Some plots in all treatments, including control plots, were contaminated at the end of year 5. Crop rotation delayed population development of H. glycines. During years 6 through 11 cv. Fayette (PI88.788 source of resistance) was planted. In year 6 numbers of cysts declined to 1/250 cm(3) of soil in the treatment consisting of monocultured Fayette. At the end of year 10, cysts were below the detection level in all treatments in which Fayette was planted. Yield of susceptible soybean in monoculture with or without H. glycines infestation was lower beginning in year 6 when compared to yield of soybean grown in rotation and remained lower throughout the duration of the experiment except for 1987 (year 9). Yields of susceptible and resistant soybean were different each year except for drought years in 1980 and 1988. From 1979 to 1982 differences in yield were due to lower yield potential of resistant cultivars. Except for the drought year, yield of cv. Fayette was greater than susceptible Williams 82 during years 6 through 11.
RESUMEN
Egg hatch and emergence of second-stage juveniles (J2) of Heterodera glycines races 3 and 4 from cysts exposed to soybean root leachate of cv. Fayette (resistant to H. glycines) and H. glycines-susceptible cultivars A2575, A3127, and Williams 82 were determined in three sets of experiments. In the first experiment, cysts of both race 3 and race 4 were exposed to leachate of 8-week-old plants for a 2-week period. In the second experiment, cysts from populations of races 3 and 4 were raised on cultivars A2575, A3127, and Williams 82. Cysts then were exposed to leachate from 8-week-old plants for a 2-week period in all possible race-per-cultivar combinations. In the third experiment, cysts of races 3 and 4 were exposed at 4-day intervals to leachate from plants as the plants developed 7 to 59 days after planting. In experiments 1 and 2, leachate from 8-week-old Williams 82 and A3127 stimulated more hatch and emergence of H. glycines than leachate from A2575, Fayette, or the control. In the first experiment, cumulative hatch and emergence were greater for race 3 than for race 4. In experiment 2, no apparent relationship developed between leachate from a cultivar and the population developed on that cultivar in terms of stimulation of hatch and emergence. In the third experiment, A2575 stimulated more hatch and emergence of both race 3 and race 4 than A3127, Fayette, and Williams 82. Leachate from Fayette stimulated less hatch and emergence of both race 3 and race 4. Hatch and emergence were greatest during the initial 12 days of the experiment.
RESUMEN
A study was conducted in growth chambers to examine main factor and interaction effects of Tylenchorhynchus nudus and Magnaporthe poae on creeping bentgrass and annual bluegrass at 24, 28, and 30 C. A 2 x 2 factorial arrangement of treatments was employed with presence and absence of T. nudus and M. poae as factors with each temperature run separately for 14 or 18 days. Tylenchorhynchus nudus decreased bentgrass and annual bluegrass root length at all three temperatures. Magnaporthe poae had no effect on bentgrass root length at 24 C, increased root length at 28 C, and suppressed root growth at 30 C. Magnaporthe poae had no effect on annual bluegrass root length at 24 and 28 C but suppressed root growth at 30 C. A significant interaction between M. poae and T. nudus occurred only on bentgrass at 28 C and 30 C; at these two temperatures, M. poae did not act independently of T. nudus.
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A study was conducted to determine the vertical distribution of Tylenchorhynchus nudus, Criconemella curvata, and Helicotylynchus cornurus in the upper 5 cm of bentgrass (Agrostis palustris cv. Penncross) putting green turf. The effect of fenamiphos on the vertical distribution of these species also was examined. Experimental design was a split-plot in which whole-plots were fenamiphos treated (0.11 kg a.i./100 m(2)) or untreated, and sub-plots were two strata (depths of 0-2.5 crn and 2.5-5.0 cm). Soil samples were collected during the growing season for 2 years after treatment to determine root weight and number of nematodes. Root weight was greater in the upper stratum on all sampling dates in both years. When differences between strata in population density were observed, T. nudus, C. curvata, and H. cornurus were more concentrated in the upper stratum. Vertical distribution of T. nudus, C. curvata, and H. cornurus was similar to the distribution of root weight. The difference in population density of H. cornurus between upper and lower strata was affected by fenamiphos on some dates, whereas differences between strata were unaffected for T. nudus and C. curvata. Double arcsine transformed proportions of the total populations of T. nudus, C. curvata, and H. cornurus in the upper stratum on each sampling date indicated no differences between fenamiphos treated and untreated plots in 1989 or 1990.
RESUMEN
Field experiments were conducted in 1989 and 1990 to examine the population fluctuation patterns of Tylenchorhynchus nudus, Criconemella curvata, and Helicotylenchus cornurus in mixed bentgrass and annual bluegrass putting greens on two golf courses near Chicago, Illinois, to determine if fluctuation patterns could be extrapolated to unsampled greens. Fenamiphos-treated and untreated plots were established on seven putting greens on two golf courses. Greens were sampled intensively five times during the growing season, and statistical comparisons of population levels per gram of root were made among dates for each green. Population levels per gram of root changed significantly on all greens in both years for each of the three nematode populations. Within a putting green in either year, population fluctuation patterns in fenamiphos-treated and untreated plots were similar. Population fluctuation patterns were different between years, however. Within a year, population fluctuation patterns among greens showed similarities indicating that carefully monitoring a few locations may allow extrapolation of population fluctuation data to other locations within that year.