RESUMEN

The lance nematode Hoplolaimus magnistylus Robbins 1982 (3) was found for the first time in Tennessee in a cotton (Gossypium hirsutum L.) field (35°19.550' N, 89°24.535' W) in Fayette County in May 2011. In June of the same year, the species was also found in soil samples collected from a corn (Zea mays L.) field (36°15.736' N, 88°51.121' W) and a soybean (Glycine max L.) field (36°15.616' N, 88°51.118' W) in Weakley County, TN. Nematodes were extracted from the soil with a semi-automatic elutriator and further processed by sugar flotation-centrifugation. Population densities were between 30 and 50 individuals per 100 cm3 of soil in areas with noticeable stunting. Helicotylenchus sp. and Pratylenchus sp. were also present at less than 10 individuals per 100 cm3 of soil. Ten soybean seeds, cv. Hutcheson, were planted and inoculated with 50 H. magnistylus per 100 cm3 in steam-sterilized soil, and were maintained in a greenhouse. Forty-five days later, soybean plants exhibited at least one of the following symptoms: stunting and chlorosis, reduced root growth, and localized root lesions. Individual nematodes were handpicked and identified under a compound light microscope as H. magnistylus based on morphological and morphometric characteristics. The main diagnostic character for this species is the size of the stylet. In the populations collected, females had stylets ranging from 49 to 58 µm (mean 56 µm). Males and females were observed with head distinctly set off and massive cephalic framework, stylet long and robust and stylet knobs pointed anteriorly. The lateral field was areolated and had four incisures most of the body length, the excretory pore was prominent and located 190 µm (175 to 200 µm) from anterior end, hemizonid was large and located one or two annules posterior to the excretory pore, phasmids were large, conspicuous, and variable in position, and vulva was prominent and near midbody. This species is most similar to the more commonly reported H. galeatus, but differs from it in the longer stylet. Total DNA was extracted from single adults from each soil sample and the species-specific primers Hoc-1f (5'-AACCTGCTGCTGGATCATTA-3') and HM-3r (5'-AGACTGGACGGCCAAAGTT-3') designed by Bae et al. (1) were used to confirm the identification by amplification of a distinct 340-bp amplicon that differentiates this species from H. columbus, H. galeatus, H. concaudajuvencus, and H. stephanus. H. magnistylus was first described from soil samples taken from a corn and soybean field in Marianna, AR (3), and has been reported in association with soybean and corn in Louisiana and Mississippi (4). Robbins (4) reported that H. magnistylus was not a serious pest of irrigated cotton in Arkansas, but there are no other pathogenicity studies published for soybean, corn, or non-irrigated cotton. Other lance species, mainly H. galeatus and H. columbus, have been reported to cause serious damage to cotton in the Carolinas and Georgia (3). Previously, H. galeatus was reported in Tennessee by Bernard (2). Lance nematodes feed as migratory endo- and ectoparasites and injure the growing points of roots, causing stunting of plants. Because so little is known about the pathogenicity of this nematode, it becomes relevant to add our records of its known distribution in field crops in the United States. To our knowledge, this is the first report of H. magnistylus in Tennessee. References: (1) C. H. Bae et al. Nematology 11:471, 2009. (2) E. C. Bernard. University of Tennessee Bulletin 594, 1980. (3) R. T. Robbins. J. Nematol. 14:500, 1982. (4) R. T. Robbins. J. Nematol. 30(4S):590, 1998.

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

Chemical investigations of some Stephania species native to Australia and reportedly employed by Aboriginal people as therapeutic agents, are described. The alkaloids from the forest vines Stephania bancroftii F.M. Bailey and S. aculeata F.M. Bailey (Menispermaceae) have been isolated and characterised. The major alkaloids in the tuber of the former species are (-)-tetrahydropalmatine and (-)-stephanine, whereas these are minor components in the leaves, from which a C-7 hydroxylated aporphine has been identified. The major tuber alkaloids in S. aculeata are (+)-laudanidine, and the morphinoid, (-)-amurine, whose absolute stereochemistry has been established by X-ray structural analysis of the methiodide derivative. No significant levels of alkaloids were detected in S. japonica. Complete and unambiguous 1H and 13C NMR data are presented for these alkaloids.

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RESUMEN

The soybean cyst nematode, Heterodera glycines, is the most economically important pathogen of soybean in Missouri. Knowledge of the nematode's distribution and ability to adapt to resistant varieties is important for determining crop losses and establishing research priorities. No previous surveys of Missouri have provided reliable population density and phenotypic diversity data; therefore, we conducted a random survey to obtain both. Two samples from each of 200 fields were collected; 392 samples were processed for extractions of cysts and eggs. Two hundred and forty seven (63%) of the samples had detectable cyst nematode populations, which ranged from 15 to 149,700 eggs per 250 cm3 of soil. The lowest average population densities were observed in the east-central region of Missouri (2,260 eggs per 250 cm3 of soil), and the highest were observed in the northeast (9,238 eggs per 250 cm3 of soil), but among the eight regions sampled, mean population densities did not differ significantly. These population densities were potentially responsible for losses worth over $58 million in 1999 in Missouri. Race tests were conducted on populations from 183 samples. In order of frequency, races 3, 1, and 2 accounted for 86% of H. glycines populations. Nearly 60% of the populations were virulent (able to produce females) on plant introduction (PI) 88788, which is the source of resistance for most H. glycines-resistant cultivars. More than a third of the populations were virulent on cv. Peking, another common resistance source. Very few populations were virulent on PI 90763 or PI 437654, suggesting that these sources of resistance should be exploited more frequently.

RESUMEN

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

Soybean cyst nematode, Heterodera glycines, is found throughout soybean production areas of the United States, but the nematode's distribution is not uniform within states, counties, and individual fields. The goal of this research was to determine the spatial pattern of H. glycines population density in a field in southeastern Missouri and whether it changed over time in the absence of management practices. Geostatistical methods were used to describe and map the distribution of H. glycines over 4 years in a soybean (Glycine max) field in southeastern Missouri. Semivariograms and kriging, an interpolation method, were used to prepare isoarithmic contour maps and associated error maps. In the field studied, fall H. glycines population density (Pf) was poorly related to density the following spring (Pi). The distribution of peak H. glycines population density within the field changed from year to year, although high densities were often detected in the same general region of the field. The patchiness of H. glycines distribution within a field was verified. Yield was not related to H. glycines egg population density at planting, indicating that unmeasured variables were also reducing yield.

RESUMEN

Previous reports of crop losses to plant-parasitic nematodes have relied on published results of survey data based on certain commodities, including tobacco, peanuts, cotton, and soybean. Reports on crop-loss assessment by land-grant universities and many commodity groups generally are no longer available, with the exception of the University of Georgia, the Beltwide Cotton Conference, and selected groups concerned with soybean. The Society of Nematologists Extension Committee contacted extension personnel in 49 U.S. states for information on estimated crop losses caused by plant-parasitic nematodes in major crops for the year 1994. Included in this paper are survey results from 35 states on various crops including corn, cotton, soybean, peanut, wheat, rice, sugarcane, sorghum, tobacco, numerous vegetable crops, fruit and nut crops, and golf greens. The data are reported systematically by state and include the estimated loss, hectarage of production, source of information, nematode species or taxon when available, and crop value. The major genera of phytoparasitic nematodes reported to cause crop losses were Heterodera, Hoplolaimus, Meloidogyne, Pratylenchus, Rotylenchulus, and Xiphinema.

RESUMEN

Polyclonal antibodies were raised against Heterodera glycines eggshells to determine the feasibility of developing an immunoassay for H. glycines eggs. An indirect enzyme-linked immunosorbent assay (ELISA) was developed from anfisera collected 10 weeks after the initial injection. From serial dilutions of sonicated eggshells or whole eggs, a sensitivity of detection to 5 ng/ml sonicated eggshells or 1 egg of H. glycines was determined. The method of eggshell preparation had no effect on the antibodies produced; however, the antibodies cross-reacted with sonicated J2 of H. glycines and eggs of Meloidogyne incognita and H. schachtii. Most of the proteins in both life stages of H. glycines and eggs of M. incognita and H. schachtii had similar migration properties when separated on SDS-PAGE gels and stained with Coomassie blue. Western blot analysis, with antisera adsorbed with homogenized J2 of H. glycines, showed proteins that were specifically localized to eggshells of H. glycines. Monoclonal antibodies might provide a useful immunoassay where polyclonal antibodies lack sufficient specificity.

RESUMEN

Experiments were conducted to determine the effects of zinc fertilizers on hatching and soil population densities of Heterodera glycines. In vitro egg hatching in solutions of reagent-grade zinc sulfate and zinc chloride and fertilizer-grade zinc sulfate was significantly greater than hatching in deionized water, whereas zinc chelate fertilizer significantly inhibited egg hatching relative to deionized water. In greenhouse experiments, no differences in cumulative percentage egg hatch were detected in soil naturally infested with H. glycines amended with fertilizer-grade zinc sulfate and zinc chelate at rates equivalent to 0, 1.12, 11.2, and 112 kg Zn/ha and subsequently planted with corn (Zea mays L.). In a field experiment, no significant differences in H. glycines egg population densities and corn yields were detected among plots fertilized with 0, 11.2, and 22.4 kg Zn/ha rates of zinc chelate. Yields of H. glycines-susceptible soybean planted in plots 1 year after zinc fertilization of corn plots also were not significantly affected. Zinc compounds significandy affected H. glycines egg hatching in vitro, but had no effect on hatching in natural soils.

RESUMEN

Greenhouse tests were conducted to determine the persistence of nonviable Heterodera glycines eggs in soil. Laboratory and greenhouse tests were conducted to determine the usefulness of the vital stains acridine orange and tetrazolium red for differentiating viable and nonviable eggs of H. glycines. Nonviable (boiled) egg preparations were compared with preparations that were not boiled for their persistence in methyl bromide-fumigated soil. Boiled eggs persisted longer (>200 days) than untreated eggs, perhaps due to disinfestation of the egg suspensions by boiling. Neither stain was a good indicator of egg viability as inferred from infectivity of juveniles in a bioassay of the same egg preparations exposed to the stains.

RESUMEN

Between May, 1988, and July, 1992, the University of Missouri Plant Nematode Diagnostic Laboratory collected data on Heterodera glycines populations in Missouri by offering diagnostic services to soybean farmers. A greenhouse bioassay (free), egg count ($10/sample), and race determination test ($25) were conducted by request on soil samples submitted to the lab. Each test was offered for a specific purpose: the bioassay for fields not known to be infested; the egg count for population monitoring in fields with known infestations; and the race test for fields with a history of resistant cultivars. Of 818 samples submitted for bioassay on a H. glycines-susceptible soybean cultivar, 13 (1.6%) contained brown cysts but no white females, and 364 (45%) contained white females after 35 days in the greenhouse. Of 6,193 egg counts, 39% were either free of H. glycines or contained fewer than 500 eggs/250 cm(3) soil, the action threshold for Missouri. The remaining 61% ranged from 500-400,000 eggs/250 cm(3) soil (mean = 10,617). Eleven races were detected, with races 3 (45%) and 1 (23%) the most common. The data show that H. glycines is widespread in Missouri (with confirmed infestations in 80 of 114 counties), that most infested fields have population densities above the action threshold, and that there is considerable genetic diversity among H. glycines field populations.