Survey of Heterodera glycines Population Densities and Virulence Phenotypes During 2015–2016 in Missouri

The soybean cyst nematode (SCN), Heterodera glycines, is one of the most important pathogens of soybean. Periodic monitoring of SCN population densities and virulence phenotypes is necessary for developing management strategies utilizing resistant cultivars, the primary strategy used to combat this pest. Therefore, we conducted a statewide survey of Missouri to determine SCN population densities and virulence phenotypes during 2015–2016 and compared these results with a similar survey conducted in 2005. SCN population densities were determined for 393 soil samples representing 74 soybean-producing counties across eight geographical regions of Missouri. Eighty-eight percent of samples tested positive for SCN, up from 50% in 2005, and population densities ranged from 125 to 99,000 eggs per 250 cm3 of soil. The virulence phenotypes of 48 SCN populations also were determined. For this, female indices (FI) were calculated by dividing the mean number of females that develop on the roots of a set of resistant soybean indicator lines by the mean number of females that develop on the roots of susceptible cultivar Lee74 after 30 days in the greenhouse then multiplying by 100 to obtain a percentage. Notably, all SCN populations evaluated during 2015–2016 had a FI > 10 on PI 88788, the most widely used source of resistance in Missouri, in contrast to 78% in 2005. Moreover, 50% of these populations had a FI > 50 on PI 88788, up from 16% in 2005. Forty-three percent of populations tested also had a FI > 10 on Peking, the second most common source of resistance by farmers. Our results show that over the last decade, SCN has become more prevalent in Missouri fields. Additionally, the percentage of individuals within SCN field populations that are virulent on PI 88788 and Peking has markedly increased. The results stress the importance of rotating cultivars with different types of resistance when using resistant cultivars to manage SCN.

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Variability in Distribution and Virulence Phenotypes of Heterodera glycines in Missouri During 2005

Plant Disease ◽

10.1094/pdis-91-11-1473 ◽

2007 ◽

Vol 91 (11) ◽

pp. 1473-1476 ◽

Cited By ~ 48

Author(s):

Melissa G. Mitchum ◽

J. Allen Wrather ◽

Robert D. Heinz ◽

J. Grover Shannon ◽

Gene Danekas

Keyword(s):

Soybean Cyst Nematode ◽

Heterodera Glycines ◽

Cyst Nematode ◽

Common Source ◽

Sources Of Resistance ◽

Resistant Cultivars ◽

Soybean Cultivars ◽

Geographical Regions ◽

Two Samples ◽

Pi 88788

The soybean cyst nematode, Heterodera glycines, is a serious economic threat to soybean producers in Missouri. Periodic monitoring for the presence, population densities, and virulence phenotypes of H. glycines is essential for determining crop losses and devising management strategies implementing the use of resistant cultivars. A survey using area-frame sampling was conducted to determine the distribution and virulence phenotypes of H. glycines in Missouri during 2005. Two samples from each of 125 fields representing eight geographical regions of Missouri were collected; 243 samples were processed for extraction of cysts and eggs. In all, 49% of samples had detectable cyst nematode populations, which ranged from 138 to 85,250 eggs per 250 cm3 of soil. Race and H. glycines type tests were conducted on populations from 45 samples. Nearly 80% of the populations that were tested, irrespective of the region, were virulent on the indicator line plant introduction (PI) 88788, which is the source of resistance for most H. glycines-resistant cultivars. More than 70% of populations could reproduce on the indicator lines PI 88788, PI 209332, and PI 548316 (Cloud), indicating that soybean cultivars with resistance derived from these sources need to be carefully monitored and used only in rotation with nonhost crops and soybean cultivars with resistance from other sources. Approximately one-third of the populations, primarily in the southern regions of Missouri, could reproduce on PI 548402 (Peking), another common source of resistance. Fewer than 10% of the populations could reproduce on PI 90763, PI 437654, PI 89772, or PI 438489B, suggesting that these sources of resistance should be used in soybean breeding programs to develop H. glycines-resistant soybean cultivars.

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Determination of Heterodera glycines Virulence Phenotypes Occurring in South Dakota

Plant Disease ◽

10.1094/pdis-04-16-0572-re ◽

2016 ◽

Vol 100 (11) ◽

pp. 2281-2286 ◽

Cited By ~ 12

Author(s):

K. Acharya ◽

C. Tande ◽

E. Byamukama

Keyword(s):

South Dakota ◽

Soybean Cyst Nematode ◽

Heterodera Glycines ◽

The United States ◽

Soil Samples ◽

Sources Of Resistance ◽

Resistant Cultivars ◽

Pi 88788 ◽

Different Sources

The soybean cyst nematode (SCN), Heterodera glycines, is the most important yield-limiting pathogen of soybean in the United States. In South Dakota, SCN has been found in 29 counties, as of 2016, and continues to spread. Determining the virulence phenotypes (HG types) of the SCN populations can reveal the diversity of the SCN populations and the sources of resistance that would be most effective for SCN management. To determine the HG types prevalent in South Dakota, 250 soil samples were collected from at least three arbitrarily selected fields in each of the 28 counties with fields previously found to be infested with SCN. SCN was detected in 82 fields (33%), and combined egg and juvenile counts ranged from 200 to 65,200 per 100 cm3 of soil. Eggs and juveniles were extracted from each soil sample and were used to infest seven SCN HG type test indicator soybean lines and ‘Williams 82’ as the susceptible check. A female index (FI) was calculated based on the number of females found on each indicator line relative to those on the susceptible check. A FI equal to or greater than 10% in any line was assigned as that HG type. Out of 73 SCN populations for which HG type tests were done, 63% had FI ≥10% on PI 548316 (indicator line #7), 25% on PI 88788 (#2), 19% on PI 209332 (#5), 7% on PI 548402 (#1), 4% on PI 90736 (#3), and 4% on PI 89722 (#6). None of the SCN populations had FI ≥10% on PI 437654 (indicator line #4). The most prevalent HG types were 0, 2.5.7, and 7. These accounted for 81% of all the HG types determined for the samples tested. HG types with ≥10% reproduction on indicator lines PI 88788, PI 209332, and PI 548317 were most prevalent in the soil samples tested, suggesting that the use of these sources of resistance for developing SCN resistant cultivars should be avoided. For sustainable SCN management, use of resistant cultivars should be rotated with nonhost crops and cultivars with different sources of resistance.

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Effect of Soybean Cyst Nematode Resistance Source and Seed Treatment on Population Densities of Heterodera glycines, Sudden Death Syndrome, and Yield of Soybean

Plant Disease ◽

10.1094/pdis-12-16-1832-re ◽

2017 ◽

Vol 101 (12) ◽

pp. 2137-2143 ◽

Cited By ~ 14

Author(s):

Yuba R. Kandel ◽

Kiersten A. Wise ◽

Carl A. Bradley ◽

Martin I. Chilvers ◽

Adam M. Byrne ◽

...

Keyword(s):

Sudden Death ◽

Soybean Cyst Nematode ◽

Seed Treatment ◽

Heterodera Glycines ◽

Plant Introduction ◽

Cyst Nematode ◽

Sudden Death Syndrome ◽

Population Densities ◽

Scn Resistance ◽

Pi 88788

A three-year study was conducted in Illinois, Indiana, Iowa, Michigan, and Ontario, Canada, from 2013 through 2015 to determine the effect of soybean (Glycine max) cultivars’ source of soybean cyst nematode (SCN; Heterodera glycines) resistance on SCN population densities, sudden death syndrome (SDS; caused by Fusarium virguliforme), and yield of soybean. Five cultivars were evaluated with and without fluopyram seed treatment at each location. Cultivars with no SCN resistance had greater SDS severity, greater postharvest SCN egg counts (Pf), and lower yield than cultivars with plant introduction (PI) 548402 (Peking) and PI 88788-type of SCN resistance (P < 0.05). Cultivars with Peking-type resistance had lower Pf than those with PI 888788-type and no SCN resistance. In two locations with HG type 1.2-, cultivars with Peking-type resistance had greater foliar disease index (FDX) than cultivars with PI 88788-type. Fluopyram seed treatment reduced SDS and improved yield compared with a base seed treatment but did not affect SCN reproduction and Pf (P > 0.05). FDX and Pf were positively correlated in all three years (P < 0.01). Our results indicate that SDS severity may be influenced by SCN population density and HG type, which are important to consider when selecting cultivars for SCN management.

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Distribution, population density, race and type determination of soybean cyst nematode, Heterodera glycines, in Iran

Nematology ◽

10.1163/156854108786161535 ◽

2008 ◽

Vol 10 (6) ◽

pp. 919-924 ◽

Cited By ~ 2

Author(s):

Mansour Salati ◽

Robert Riggs ◽

Zahra Tanha Maafi

Keyword(s):

Soybean Cyst Nematode ◽

Heterodera Glycines ◽

Growing Season ◽

Cyst Nematode ◽

Soil Samples ◽

Population Densities ◽

Northern Iran ◽

Second Stage ◽

The World

AbstractThe soybean cyst nematode (SCN), Heterodera glycines, found in most soybean growing regions in the world, is considered the most economically damaging pathogen of soybean worldwide. A survey conducted in the northern provinces of Mazandaran and Golestan, the main soybean-producing areas in Iran, revealed SCN was widespread in different localities of these regions. Of the 55 and 88 soil samples collected from soybean fields in Mazandaran and Golestan provinces, respectively, ten (18.8%) and 23 (26%) samples were infested with H. glycines; the population densities of second-stage juveniles (J2) and eggs ranged from 500 to 60 000 and 500 to ≥100 000 per 250 cm3 soil, respectively. These population densities of H. glycines are indicative of reductions in soybean yield. HG Type tests were conducted on 16 field populations. HG Type 0 (race 3) was the most common with 94% frequency, whereas HG Type 7 (race 6) was found in 6% of tested populations. Most populations of H. glycines parasitised PI88788 and PI548316. Eight of the most commonly used soybean cultivars were tested against H. glycines HG Type 0; seven of them, Sepideh, Sahar (Pershing), Gorgan 3, Williams 82, JK (Sari), BP (Telar) and Hill, had high female indices and were considered susceptible to HG Type 0. Only the cultivar DPX showed low female indices and was resistant to race 3. The initial observations showed that the first life cycle of SCN required 30-34 days in early-planted fields (late May and early June), whereas in late-planted fields (early July), white females were visible 20 days after planting. Several generations could be expected in a single growing season under field conditions in northern Iran.

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Soybean Cyst Nematode Reduces Soybean Yield Without Causing Obvious Aboveground Symptoms

Plant Disease ◽

10.1094/pdis.2003.87.6.623 ◽

2003 ◽

Vol 87 (6) ◽

pp. 623-628 ◽

Cited By ~ 50

Author(s):

J. Wang ◽

T. L. Niblack ◽

J. A. Tremain ◽

W. J. Wiebold ◽

G. L. Tylka ◽

...

Keyword(s):

Seed Development ◽

Soybean Cyst Nematode ◽

Field Experiments ◽

Heterodera Glycines ◽

Biomass Accumulation ◽

Cyst Nematode ◽

Southern Illinois ◽

Resistant Cultivars ◽

Wide Range ◽

Growth Development

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.

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Soybean Stem Colonization by Genotypes A and B of Cadophora gregata Increases with Increasing Population Densities of Heterodera glycines

Plant Disease ◽

10.1094/pd-90-1297 ◽

2006 ◽

Vol 90 (10) ◽

pp. 1297-1301 ◽

Cited By ~ 4

Author(s):

G. M. Tabor ◽

G. L. Tylka ◽

C. R. Bronson

Keyword(s):

Population Density ◽

Soybean Cyst Nematode ◽

Heterodera Glycines ◽

Cyst Nematode ◽

Stem Rot ◽

Population Densities ◽

Brown Stem Rot ◽

Phialophora Gregata ◽

Soybean Genotypes ◽

Genotype A

Growth chamber experiments were conducted to investigate whether parasitism by increasing population densities of Heterodera glycines, the soybean cyst nematode, increases the incidence and severity of stem colonization by the aggressive genotype A and the mild genotype B of Cadophora gregata (Phialophora gregata), causal agents of brown stem rot of soybeans. Soybean genotypes with three combinations of resistance and susceptibility to H. glycines and genotype A of C. gregata were inoculated with each genotype of C. gregata alone or each genotype with two population densities of H. glycines eggs, 1,500 or 10,000 per 100 cm3 of soil. Stems of two H. glycines-susceptible soybeans were more colonized by both aggressive and mild genotypes of C. gregata in the presence of high than in the presence of low H. glycines population density.

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Response of Heterodera glycines and Soybean Cultivar to Tillage and Row Spacing

Plant Disease ◽

10.1094/pdis.2001.85.3.311 ◽

2001 ◽

Vol 85 (3) ◽

pp. 311-316 ◽

Cited By ~ 21

Author(s):

S. Y. Chen ◽

W. C. Stienstra ◽

W. E. Lueschen ◽

T. R. Hoverstad

Keyword(s):

Population Density ◽

Soybean Cyst Nematode ◽

Heterodera Glycines ◽

Resistant Cultivar ◽

Row Spacing ◽

Initial Population ◽

Susceptible Cultivar ◽

Nematode Density ◽

Nematode Reproduction ◽

Resistant Cultivars

Heterodera glycines, commonly known as the soybean cyst nematode (SCN), has become a major factor in soybean production in the Midwest United States. The influence of five tillage treatments and two treatments of row spacing on SCN population dynamics and yield of SCN-resistant and -susceptible soybean cultivars was investigated in a corn-soybean rotation system in southern Minnesota from 1993 to 1996. No effects of tillage and row spacing were observed on nematode population density. As expected, the susceptible cultivar Sturdy consistently supported higher nematode densities than did the resistant cultivar Bell in 1993 to 1995 and Freeborn in 1996. Nematode reproduction varied among years. Predicted nematode density at equilibrium was 3,800, 13,000, 12,000, and 27,000 eggs per 100 cm3 of soil in plots with the susceptible cultivar and 480, 240, 430, and 700 eggs per 100 cm3 of soil in plots with the resistant cultivars in 1993, 1994, 1995, and 1996, respectively. The effects of tillage and row spacing on soybean yield were inconsistent. The resistant cultivars yielded 653, 195, and 435 kg/ha more (P < 0.05) than the susceptible cultivar in 1994, 1995, and 1996, respectively, but no yield difference between susceptible and resistant cultivars was observed in 1993. Planting resistant cv. Bell increased the yield of the following susceptible cv. Sturdy compared with continual planting of the susceptible cultivar. A sequence with continued resistant cultivar or cultivars, however, produced a higher overall yield and lower nematode density at the end of the 4-year rotation cycle than any sequence in which the susceptible cultivar was included. Yield of resistant and susceptible cultivars was negatively related to the SCN initial population density.

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Distribution and Virulence Phenotypes of Heterodera glycines in Missouri

Plant Disease ◽

10.1094/pdis.2003.87.8.929 ◽

2003 ◽

Vol 87 (8) ◽

pp. 929-932 ◽

Cited By ~ 15

Author(s):

T. L. Niblack ◽

J. A. Wrather ◽

R. D. Heinz ◽

P. A. Donald

Keyword(s):

Soybean Cyst Nematode ◽

Heterodera Glycines ◽

Phenotypic Diversity ◽

Research Priorities ◽

Plant Introduction ◽

Cyst Nematode ◽

Population Densities ◽

Sources Of Resistance ◽

Resistant Varieties ◽

Two Samples

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.

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Increase in Soybean Cyst Nematode Virulence and Reproduction on Resistant Soybean Varieties in Iowa From 2001 to 2015 and the Effects on Soybean Yields

Plant Health Progress ◽

10.1094/php-rs-16-0062 ◽

2017 ◽

Vol 18 (3) ◽

pp. 146-155 ◽

Cited By ~ 23

Author(s):

Michael T. McCarville ◽

Christopher C. Marett ◽

Mark P. Mullaney ◽

Gregory D. Gebhart ◽

Gregory L. Tylka

Keyword(s):

Soybean Cyst Nematode ◽

Field Experiments ◽

Yield Loss ◽

Plant Introduction ◽

Cyst Nematode ◽

Population Densities ◽

Sources Of Resistance ◽

Nematode Reproduction ◽

Soybean Yield ◽

Pi 88788

Management of the soybean cyst nematode (SCN) relies heavily on use of SCN-resistant soybean varieties to limit nematode reproduction and minimize yield loss. For Iowa, almost all SCN-resistant soybean varieties contain SCN resistance genes from a breeding line named Plant Introduction (PI) 88788. Iowa State University conducts experiments to evaluate numerous SCN-resistant and three to four SCN-susceptible soybean varieties in up to nine field experiments across Iowa each year. Data on SCN population density, virulence (SCN race and HG type), soybean yield, precipitation, and growing degree days from more than 25,000 four-row plots in field experiments conducted from 2001 to 2015 were analyzed to determine how these factors affected SCN reproduction and yield. SCN population densities were positively correlated with temperatures and negatively associated with precipitation during the growing seasons, indicating that SCN reproduction was greatest in hot, dry years. Over the years, virulence of SCN populations on PI 88788 increased in the fields in which the experiments were conducted, resulting in increased end-of-season SCN population densities and reduced yields of SCN-resistant soybean varieties with the PI 88788 source of resistance. These results indicate that soybean yield loss caused by SCN on resistant varieties with the common PI 88788 source of resistance likely will increase as virulence of SCN populations increases unless new sources of resistance become widely available and used in the future.

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Resistance to Brown Stem Rot in Soybean Germ Plasm with Resistance to the Soybean Cyst Nematode

Plant Disease ◽

10.1094/pdis.2004.88.7.761 ◽

2004 ◽

Vol 88 (7) ◽

pp. 761-768 ◽

Cited By ~ 11

Author(s):

T. J. Hughes ◽

N. C. Kurtzweil ◽

B. W. Diers ◽

C. R. Grau

Keyword(s):

Soybean Cyst Nematode ◽

Field Experiments ◽

Germ Plasm ◽

Cyst Nematode ◽

Stem Rot ◽

Brown Stem Rot ◽

Resistant Cultivars ◽

Greenhouse Experiments ◽

Scn Resistance ◽

Pi 88788

The soybean cyst nematode (SCN) and Phialophora gregata f. sp. sojae, the causal agent of brown stem rot (BSR), are two pathogens of soybean commonly found in the same field throughout the north-central United States. Field experiments designed to study the role of SCN-resistant germ plasm in soybean production have led to data suggesting that some sources of SCN resistance also may provide resistance to BSR. Soybean germ plasm with resistance to SCN was evaluated in greenhouse and field environments for resistance to BSR development based on the percentage of host tissue symptomatic of BSR. Comparison of SCN-resistant cultivars and plant introductions (PI) to standard BSR-resistant and -susceptible checks were conducted in two greenhouse experiments using a root-dip inoculation with a single isolate of P. gregata. For both greenhouse experiments, PI 209332 was the only source of SCN resistance with resistance to BSR similar to standard BSR-resistant checks. Nine other sources of SCN resistance, including PI 88788 and Peking, expressed BSR symptom severity similar to BSR-susceptible checks. Cultivars derived from most SCN-resistant sources, including PI 209332, also were susceptible to BSR development, while four of the five cultivars derived from PI 88788 were highly resistant to BSR development. SCN-resistant cultivars derived from PI 88788, Peking, and PI 209332 were planted along with standard BSR-resistant and -susceptible checks at two field locations naturally infested with P. gregata and SCN or P. gregata alone. As in greenhouse experiments, four of the five cultivars derived from PI 88788 expressed resistance to BSR development equal to or better than standard BSR-resistant checks at both locations. In contrast, cultivars derived from PI 209332 and Peking expressed varying levels of disease development depending on field environment. Yields observed for PI 88788-derived cultivars were higher than BSR-resistant checks regardless of the presence of SCN. Data from both greenhouse and field experiments suggest that cvs. Williams and Williams 82 may contain a gene or genes for BSR resistance that require one or more modifier genes, possibly located in the genome of PI 88788, for complete expression.

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