Article

Susceptibility of cover crop plants to Fusarium virguliforme , causal agent of soybean sudden death syndrome, and Heterodera glycines , the soybean cyst nematode

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Abstract

Greenhouse studies were conducted to evaluate the susceptibility of cover crop species to infection by Fusarium virguliforme (Fv), a soilborne fungus that causes sudden death syndrome (SDS) of soybean (Glycine max [L.] Merr.), and the soybean cyst nematode (SCN; Heterodera glycines), both important soybean pathogens. In the SDS experiments, cover crops were planted in Fv-infested soil, and plants were assessed for fresh biomass, root rot severity, foliar symptoms, and amount of Fv DNA in roots. Inoculated alfalfa (Medicago sativa L.), crimson clover (Trifolium incarnatum L.), red clover (Trifolium pratense L.), and pea (Pisum sativum L.) had more root necrosis than the noninoculated controls, and Fv DNA quantities in roots did not differ from those found in soybean roots. Inoculated alfalfa, corn (Zea mays L.), crimson clover, oat (Avena sativa L.), red clover, sorghum (Sorghum bicolor L.), and turnip (Brassica rapa L.) plants had lower biomass compared to noninoculated controls, although corn, oat, and turnip had no root necrosis. Biomass reduction and root necrosis were not observed in inoculated hairy vetch (Vicia villosa Roth), false flax (Camelina sativa [L.] Crantz), millet (Pennisetum glaucum [L.] R.Br.), mustard (Brassica juncea L.), rye (Secale cereale L.), ryegrass (Lolium multiflorum Lam.), triticale (Triticale hexaploide Lart.), and wheat (Triticum aestivum L.), and Fv DNA quantity in the roots of these species was lower than in soybean. These results suggest that the legume species tested are hosts of Fv whereas grasses and Brassicas spp. are nonhosts or poor hosts. In the SCN experiment, select leguminous and nonleguminous cover crop plants were grown in soil naturally infested with SCN, and the number of females formed per root after 30 days was determined. There were very few (zero to five) SCN females on the roots of multiple varieties of leguminous cover crop species studied. No females were recovered from the roots of any of the nonleguminous species studied, except for a single female on four plants from three different species. None of the cover crop plants studied were susceptible hosts for SCN. With the increasing interest in using cover crops as a soil conservation practice in corn-soybean production systems, it is important to understand how this practice would impact major soybean diseases. Knowing the impact that cover crops may have on SDS and SCN is important to help farmers make better decisions when planting cover crops in areas with history of these diseases. © 2017 Soil and Water Conservation Society. All rights reserved.

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... Recently, two field populations of SCN were tested for reproduction in brown mustard cv. Kodiak and other cover crops in greenhouse conditions in Iowa, and both SCN populations were not able to reproduce or had very limited reproduction on those crops (Kobayashi-Leonel et al., 2017). However, the effect of those crops on SCN population reduction has not been reported in the northern Great Plains. ...
... Similar to the present study, brown mustard cv. Kodiak was reported to be a non-host of SCN in Iowa (Kobayashi-Leonel et al., 2017). Additionally, Wen et al. (2017) tested a different brown mustard cv. ...
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Industrial oilseeds have a great potential in the northern Great Plains both as oilseeds and as cover crops sown following wheat (Triticum aestivum L.) harvest and before soybean [Glycine max (L.) Merr.] sowing in the following spring. One of the most important biotic stresses in soybean production is soybean cyst nematode (Heterodera glycines Ichinohe, SCN), a serious pest that affects 90% of the soybean producing areas in the U.S. The objective of this study was to evaluate the host status of and the SCN population reduction by, winter camelina [Camelina sativa (L.) Crantz, cv. Joelle], crambe (Crambe abyssinica Hochst. Ex R.E.Fr., cv. BelAnn), and brown mustard (Brassica juncea L. cv. Kodiak). The experiments were performed in a growth chamber at 27°C for 35 days by planting the crops in soil naturally infested with SCN and autoclaved sandy soil artificially inoculated with two SCN populations from two fields in North Dakota. Soybean cyst nematode did not reproduce on brown mustard or camelina with a female index (FI) of 0, suggesting these are non-hosts, while it reproduced on crambe. The numbers of white females on crambe ranged from 1 to 13 per plant with FI of 0.2 to 1.1 in naturally infested soils, and 1 to 4 per plant with FI of 1.2 to 2.5 in artificially infested soils, thus crambe would be classified as a poor-host (FI < 10). Brown mustard and winter camelina reduced the SCN populations by an average of 51% and 48%, respectively, while crambe only reduced the populations by an average of 24%, across all the experiments with naturally infested soils when compared with the initial population levels. Both brown mustard and camelina consistently reduced the SCN populations but crambe did not steadily reduce the SCN populations when compared with the non-planted control (fallow). Further understanding the effects of these crops on SCN populations under natural field conditions is needed to determine if cover crops can be used for sustainable SCN management in SCN-infested soybean fields.
... However, while camalexin production was induced by S. sclerotiorum inoculation, the relative degree of disease resistance was not correlated with levels of camalexin production, suggesting that other antimicrobial activities might be responsible for the observed disease resistance [142]. C. sativa also shows resistance to the soil-born fungus Fusarium virguliforme [144]. However, C. sativa is susceptible to other fungal diseases common to the Brassicaceae, such as damping-off (caused by Rhizoctonia solani), clubroot (Plasmodiophora brassicae Woronin.), and white rust (Albugo candida Pers. ...
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Camelina sativa (L.) Crantz. is an annual oilseed crop within the Brassicaceae family. C. sativa has been grown since as early as 4000 BCE. In recent years, C. sativa received increased attention as a climate-resilient oilseed, seed meal, and biofuel (biodiesel and renewable or green diesel) crop. This renewed interest is reflected in the rapid rise in the number of peer-reviewed publications (>2300) containing “camelina” from 1997 to 2021. An overview of the origins of this ancient crop and its genetic diversity and its yield potential under hot and dry growing conditions is provided. The major biotic barriers that limit C. sativa production are summarized, including weed control, insect pests, and fungal, bacterial, and viral pathogens. Ecosystem services provided by C. sativa are also discussed. The profiles of seed oil and fatty acid composition and the many uses of seed meal and oil are discussed, including food, fodder, fuel, industrial, and medical benefits. Lastly, we outline strategies for improving this important and versatile crop to enhance its production globally in the face of a rapidly changing climate using molecular breeding, rhizosphere microbiota, genetic engineering, and genome editing approaches.
... However, while several species of legumes used as cover crops, such as Trifolium spp, Medicago sativa, and Pisum sativum, are considered hosts of F.v., other legumes, grasses, cereals, and Brassicaceae cover crops, such as Vicia villosa, Camelina sativa, Brassica juncea, Pennisetum glaucum, Secale cereale, Lolium multiflorum, Triticale hexaploide, and Triticum aestivum, are nonhosts or poor hosts. 85 Therefore, knowledge of the susceptibility of cover crops to SDS-causing Fusarium species can help farmers choose which species should be planted in field plots with a history of SDS epidemics. Similarly, recent research reported promising results when green manure amendments were tested for SDS suppression in experimental plots in the greenhouse. ...
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The increase in food production requires reduction of the damage caused by plant pathogens, minimizing the environmental impact of management practices. Soil‐borne pathogens are among the most relevant pathogens that affect soybean crop yield. Soybean sudden death syndrome (SDS), caused by several distinct species of Fusarium, produces significant yield losses in the leading soybean producing countries in North and South America. Current management strategies for SDS are scarce since there are no highly resistant cultivars, and only a few fungicide seed treatments are available. Because of this, innovative approaches for SDS management need to be developed. Here, we summarize recently explored strategies based on plant nutrition, biological control, priming of plant defenses, host‐induced gene silencing, and the development of new SDS‐resistance cultivars using precision breeding techniques. Finally, sustainable management of SDS should also consider cultural control practices with minimal environmental impact. This article is protected by copyright. All rights reserved.
... In fact, higher levels of F. virguliforme DNA were detected in soil from the 2-year system compared with the 4-year system (Leandro et al., 2018). In a different study, the susceptibility of 15 cover crop species belonging to 13 different genera together with two soybean cultivars and one maize hybrid planted in F. virguliforme-infested soil was evaluated (Kobayashi-Leonel et al., 2017). Four inoculated cover crops (alfalfa, crimson clover, red clover, and pea) had more root symptoms than the uninoculated control, seven inoculated crops (alfalfa, maize, crimson clover, oat, red clover, sorghum, and turnip) had a lower biomass than the respective Canada (Ontario) showed no correlation between early planting date and SDS severity (Kandel et al., 2016b). ...
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Soybean sudden death syndrome (SDS) is a fungal disease caused by members of clade 2 of the Fusarium solani species complex (FSSC). These fungi are soilborne pathogens that infect soybean plants through the roots and produce toxins that translocate to aerial parts of the plant, inducing foliar chlorosis and necrosis followed by premature defoliation. Here, we first give the current state of knowledge of early pathogen detection and infection establishment for the SDS pathosystem. Subsequently, we discuss the nature and activity of secreted toxins, followed by an overview of changes in plant metabolism and factors that influence fungus–soybean interaction. Finally, we summarize the advances in plant disease resistance, symptom evaluation, and treatment. The current state of knowledge of soybean sudden death syndrome‐causing Fusarium species pathogenesis, fungi–soybean interaction and plant disease resistance, symptom evaluation, and treatment is reviewed.
... A study by Kobayashi-Leonel et al. (2017) showed that alfalfa, Austrian winter pea, berseem clover (Trifolium alexandrinum L.), cowpea, crimson clover, field pea, hairy vetch (two different cultivars), red clover (three different cultivars), and white clover (two different cultivars) supported SCN reproduction at very low level, suggesting poor hosts. Our results support their findings that Austrian winter pea, crimson clover, field pea (Aragorn and Cooper), and hairy vetch were poor host/suitable hosts but alfalfa, cowpea, and berseem clover were non-hosts for both SCN populations in our study. ...
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Soybean cyst nematode (SCN; Heterodera glycines) reproduces on a wide range of plants, including some cover crops. However, reproduction of SCN populations on a number of cover crops has not been investigated in the northern Great Plains. Thirty-five cover crop species/cultivars from four plant families were evaluated as hosts for SCN. Greenhouse evaluations were done with two common SCN populations, SCN103 (HG type 0) and SCN2W (HG type 7) under controlled conditions. The sources of two SCN populations were two soybean fields of North Dakota. After 35 days of growth, white SCN females were extracted from individual plants and counted to determine a female index (FI = average number of females on a tested crop/average number of females in a susceptible check x 100) for each crop. Out of the 35 cover crop species/cultivars tested, at least one of the SCN populations reproduced on seven crops/cultivars but did not reproduce on the other 28 crops/cultivars. Out of these seven crops, only white lupine (Lupinus albus L.) was a suitable host (FI ≥ 10) for both SCN populations in all the experiments, while others showed varied responses from poor host to suitable host for the SCN populations. The host crops were from the family Brassicaceae or Fabaceae, while all the crops in the Linaceae or Poaceae family were non-hosts. The non-host crops can be planted in SCN-infested fields without the concern of increasing SCN populations, while poor hosts with low female index should be evaluated for effects on reduction of SCN numbers in the fields before they are used as cover crops in a soybean cropping system.
... By contrast, Kobayashi-Leonel and her colleagues reported that the cover crops like alfalfa, red clover and pea can harbor soilborne pathogen like F. virguiliforme (soybean sudden death). Thus, careful selection of crops for rotation is recommended [55]. Moreover, Hiddink and his collegues reported the null effect of mixed cropping of soil with brussels sprouts and barley or with triticale and white clover [56]. ...
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Soybean sudden death syndrome (SDS) pathogens and dry bean root-rot pathogens were studied taxonomically, phylogenetically, and pathologically. Detailed phenotypic comparisons of macro- and microscopic features and phylogenetic analyses of multilocus DNA sequence data, including those on the nuclear ribosomal intergenic spacer region and the single copy nuclear gene translation elongation factor 1-a, indicated that they comprised five distinct species of Fusarium. Two new species causing soybean SDS in Brazil, F. brasiliense and F. cuneirostrum, are formally described. Fusarium cuneirostrum is responsible for soybean SDS in Brazil and dry bean or mung bean root-rot in the United States, Canada, and Japan. Strains of each species, including F. cuneirostrum isolates from dry bean and mung bean and F. phaseoli isolates from dry bean, were inoculated on soybean cultivar Pioneer 9492RR to determine their pathogenicity. Although intraspecific variation in pathogenicity was observed, all the species were able to induce typical SDS symptoms on soybean plants in the artificial inoculation tests. Comparisons of the key diagnostic morphological features reveal that all five species can be diagnosed using conidial morphology.
Article
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Seven different 2-year rotations, consisting of barley/clover, canola, green bean, millet/rapeseed, soybean, sweet corn, and potato, all followed by potato, were assessed over 10 years (1997–2006) in a long-term cropping system trial for their effects on the development of soilborne potato diseases, tuber yield, and soil microbial communities. These same rotations were also assessed with and without the addition of a fall cover crop of no-tilled winter rye (except for barley/clover, for which underseeded ryegrass was substituted for clover) over a 4-year period. Canola and rapeseed rotations consistently reduced the severity of Rhizoctonia canker, black scurf, and common scab (18 to 38% reduction), and canola rotations resulted in higher tuber yields than continuous potato or barley/clover (6.8 to 8.2% higher). Addition of the winter rye cover crop further reduced black scurf and common scab (average 12.5 and 7.2% reduction, respectively) across all rotations. The combined effect of a canola or rapeseed rotation and winter rye cover crop reduced disease severity by 35 to 41% for black scurf and 20 to 33% for common scab relative to continuous potato with no cover crop. Verticillium wilt became a prominent disease problem only after four full rotation cycles, with high disease levels in all plots; however, incidence was lowest in barley rotations. Barley/clover and rapeseed rotations resulted in the highest soil bacterial populations and microbial activity, and all rotations had distinct effects on soil microbial community characteristics. Addition of a cover crop also resulted in increases in bacterial populations and microbial activity and had significant effects on soil microbial characteristics, in addition to slightly improving tuber yield (4% increase). Thus, in addition to positive effects in reducing erosion and improving soil quality, effective crop rotations in conjunction with planting cover crops can provide improved control of soilborne diseases. However, this study also demonstrated limitations with 2-year rotations in general, because all rotations resulted in increasing levels of common scab and Verticillium wilt over time.
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This article reviews literature about the impacts of cover crops in cropping systems that affect soil and water quality and presents limited new information to help fill knowledge gaps. Cover crops grow during periods when the soil might otherwise be fallow. While actively growing, cover crops increase solar energy harvest and carbon flux into the soil, providing food for soil macro and microorganisms, while simultaneously increasing evapotranspiration from the soil. Cover crops reduce sediment production from cropland by intercepting the kinetic energy of rainfall and by reducing the amount and velocity of runoff. Cover crops increase soil quality by improving biological, chemical and physical properties including: organic carbon content, cation exchange capacity, aggregate stability, and water infiltrability. Legume cover crops contribute a nitrogen (N) to subsequent crops. Other cover crops, especially grasses and brassicas, are better at scavenging residual N before it can leach. Because growth of these scavenging cover crops is usually N limited, growing grass/legume mixtures often increases total carbon inputs without sacrificing N scavenging efficiency. Cover crops are best adapted to warm areas with abundant precipitation. Water use by cover crops can adversely impact yields of subsequent dryland crops in semiarid areas. Similarly, cooler soil temperatures under cover crop residues can retard early growth of subsequent crops grown near the cold end of their range of adaptation. Development of systems that reduce the costs of cover crop establishment and overcome subsequent crop establishment problems will increase cover crop utilization and improve soil and water quality.
Article
Soybean sudden death syndrome (SDS), caused by Fusarium virguliforme, is an economically important soilborne disease and is a major risk to many soybean [Glycine max, (L.) Merr.] production regions worldwide. Two-year studies were conducted in a greenhouse and in fields to examine survival of the fungus in corn-soybean residues. Corn kernels consistently showed significantly (P<0.05) higher F. virguliforme colony-forming units per gram of dry soil (CFU/g) in a greenhouse and in field micro-plots compared to no additional residue added treatment (control). None of the soil samples from commercial fields in Iowa showed significant (P<0.05) difference in F. virguliforme CFU/g within year of sampling, but between years there were numerical differences but not statistically different in samples if the previous crop had been corn, compared with winter wheat or soybean. In Fusarium spp. not causing SDS, CFU/g were significantly (P<0.05) higher in micro-plots amended with six different corn-soybean residue treatments compared with the control in 2008, while in 2009, only corn stock spread on soil showed significant (P<0.05) difference over the control. Our results suggest that a clean corn harvest could reduce SDS risk by reducing colonization of corn kernels that supports survival of F. virguliforme, while a considerable corn loss during harvest could increase SDS risk.
Article
Cover crops can improve the sustainability and resilience of corn (Zea mays L.) and soybean (Glycine max L. Merr.) production systems. At present, the most widely used cover crops in corn-soybean systems in the upper Midwest United States have been winter cereals. However, there have been isolated reports of corn yield reductions following winter rye (Secale cereale L.) cover crops, and the risk of corn yield reductions will reduce the likelihood of farmers adopting cover crops. Although the exact mechanism is unknown and there are many possible causes of corn yield reductions following winter cereal cover crops, we hypothesize that there may be differences among winter cereal species or cultivars in their effect on corn yield. Additionally, there have been no evaluations of shoot growth and nitrogen (N) uptake of winter cereal cultivars used as cover crops in the upper Midwest. Seven winter rye cultivars, 2 winter triticale (× Triticosecale Wittmack) cultivars, and 3 winter wheat (Triticum aestivum L.) cultivars were planted following soybean harvest and grown as a winter cover crops preceding corn in four years to determine whether the 12 cultivars differed in (1) biomass production and N uptake, and (2) impact on corn yield, harvest population, and other yield parameters. The 12 cover crop cultivars differed in each of the four years for shoot dry weight, shoot N concentration, and total shoot N content. In general, the winter rye cultivars had greater shoot biomass, lower shoot N concentrations, and higher total shoot N contents than the winter triticale and winter wheat cultivars. The winter cereal cultivars decreased corn yield in two of the four years, and the yield effect varied among cultivars. Some cultivars of all three species caused corn yield decreases, with no indication that winter rye had a greater effect than did winter wheat or winter triticale. Four winter rye cultivars did not significantly reduce corn yield in either of the two years in which yield was reduced. In general, the decreases in corn yield following the winter cereal cover crops were related to decreases in harvest population and increases in the number of barren plants, but were not strongly related to cover crop shoot dry weight within years. Our study shows that there are genotypic differences among winter cereal cultivars for their performance as cover crops and their effect on corn yields.
Article
This book, divided into three parts, provides a wide range of information on plant-parasitic nematodes. The chapters in Part I presents the basic structures of nematodes, followed by a chapter on molecular taxonomy, systematics and phylogeny. The subsequent four chapters focus on the major groups of plant-parasitic nematodes, presenting information on their morphology, taxonomy, basic biology and management. Part II deals with nematode biology and plant nematode interactions. Part III focuses on quantitative nematology and management.
Article
Research must focus on management of diseases that cause extensive losses, especially when funds for research are limited. Knowledge of the losses caused by various soybean diseases is essential when prioritizing research budgets. The objective of this project was to compile estimates of soybean yield potential losses caused by diseases for each soybean producing state in the United States from 2006 to 2009. This data is of special interest since the 4-year period summarized in this report, permits an examination of the impact of soybean rust that was first reported in the United States in 2004. Thus, in addition to the goal of providing this information to aid funding agencies and scientists in prioritizing research objectives and budgets, an examination of the impact of soybean rust on soybean yield losses relative to other diseases is warranted. Yield losses caused by individual diseases varied among states and years. Soybean cyst nematode caused more yield losses than any other disease during 2006 to 2009. Seedling diseases, Phytophthora root and stem rot, sudden death syndrome, Sclerotinia stem rot, and charcoal rot ranked in the top six of diseases that caused yield loss during these years. Soybean yield losses due to soybean rust and Sclerotinia stem rot varied greatly over years, especially when compared to other diseases. Accepted for publication 21 October 2010. Published 22 November 2010.
Article
Fusarium virguliforme causes soybean sudden death syndrome (SDS) in the United States. The disease was first observed in Arkansas in 1971, and since has been reported in most soybean-producing states, with a general movement from the southern to the northern states. In addition to F. virguliforme, three other species, Fusarium brasiliense, Fusarium crassistipitatum, and Fusarium tucumaniae, have been reported to cause SDS in South America. Yield losses caused by F. virguliforme range from slight to 100%. Severely infected plants often have increased flower and pod abortion, reduced seed size, increased defoliation, and prematurely senescence. Foliar symptoms observed in the field are most noticeable from mid to late reproductive growth stages. To manage SDS, research on crop rotations, soil types, tillage practices, seed treatments, and the development and utilization of host resistance has been investigated. This review focuses on what is known about F. virguliforme, the management of SDS in the United States, and how genetic engineering along with other traditional management options may be needed as integrated approaches to manage SDS.
Article
Current greenhouse screening methods for soybean [Glycine max (L.) Merr.] sudden death syndrome (SDS) are not sensitive enough to evaluate progeny of resistant x resistant crosses, which can possess resistance alleles at up to 12 quantitative trait loci (QTL). The objective of the study was to modify the current greenhouse screening method, the layer method, to increase its sensitivity in distinguishing SDS-resistant lines. Three experiments were conducted using infested sorghum [Sorghum bicolor (L.) Moench] as inoculum. In Exp. 1, five different inoculum densities (1:1, 1:5, 1:10, 1:15, and 1:20 inoculum:soil ratio) were compared, and the optimum density to distinguish genotypes was identified. In Exp. 2, the association between SDS field ratings and greenhouse severity scores was determined. In Exp. 3, the inoculum layer method was compared to the proposed modified mixed method. Inoculum ratios 1:15 and 1:20 showed the largest difference in SDS ratings between soybean genotypes. The best time to assess disease severity was 30 to 36 d after planting (DAP), with the highest correlation with field ratings at 36 DAP (r = 0.82, p < 0.05). The proposed modified method shifted the frequency distribution of SDS scores toward a normal curve. The findings indicate that the modified screening method using a 1:20 inoculum:soil ratio correlated well with field data and provided adequate screening of lines possessing up to 12 SDS resistant QTL without negatively impacting germination.
Article
Kolander, T. M., Bienapfl, J. C., Kurle, J. E., and Malvick, D. K. 2012. Symptomatic and asymptomatic host range of Fusarium virguliforme, the causal agent of soybean sudden death syndrome. Plant Dis. 96:1148-1153. Sudden death syndrome, caused by Fusarium virguliforme, is an important disease of soybean in the United States. Fifteen species of crops, weeds, or prairie plants were evaluated for their potential as hosts of F virguliforme. Root and foliar symptoms and plant biomass were assessed following greenhouse inoculation studies. Root colonization of F virguliforme was determined with isolations and with polymerase chain reaction assays. Soybean, alfalfa, pinto and navy bean, white and red clover, pea, and Canadian milk vetch developed root necrosis. Soybean, alfalfa, and red clover also developed foliar symptoms following inoculation. Sugar beet and canola did not develop symptoms but had significant reductions in biomass, suggesting that they are also hosts of E virguliforme. Corn, wheat, ryegrass, pigweed, and lambsquarters did not develop symptoms. However, these species appeared to be asymptomatic hosts because quantities of pathogen DNA detected in inoculated roots were similar to quantities detected in inoculated soybean roots. These results suggest that the number and diversity of hosts for E virguliforme are greater than previously reported. The likely broad host range limits the efficacy of crop rotation and indicates that crops other than soybean can be damaged by F virguliforme and maintain or increase inoculum in soil.
Article
Sudden death syndrome, caused by Fusarium solani f. sp. glycines, has caused severe damage to soybean production in recent years. One way to control sudden death syndrome is with resistant cultivars. Over a 3-year period, 2,335 publicly and privately developed soybean entries were inoculated and evaluated for their response to F solani f. sp. glycines under greenhouse conditions. The entries were compared with the susceptible check, Great Lakes 3302 (GL3302), and the moderately resistant checks, plant introductions (Pis) 520733 and 567374. Thirty-eight entries were identified with moderate levels of resistance. Based on foliar ratings, there were no differences (P < 0.05) between the Roundup Ready and conventional cultivars. In all, 90 ancestral lines that represent 99% of the genes in modern U.S. cultivars and 55 lines found in the pedigrees of public cultivars reported to have some resistance were evaluated for their response to F solani f. sp. glycines. Nine ancestral lines (Aoda, Kim, Jackson, Sioux, Mammoth Yellow, T 117, PI 171450, PI 54615-1, and PI 71506) and 12 cultivars or experimental lines (Ina, D83-3349, LN98-4340. LN83-2356, Hartwig, Harosoy, Bedford, Merit, Cutler, Calland, Hill, and Evans) had disease ratings not significantly different (P < 0.05) from PI 520733 or PI 567374. PI 54610. a putative ancestral line, also was found to be moderately resistant.
Article
The soybean cyst nematode (SCN), Heterodera glycines, is a major soybean yield-limiting factor, and the use of resistant cultivars is one of the most effective means to manage the nematode. During the past decade, a number of resistant cultivars in maturity groups I and II have been developed and made available to growers. A total of 47 resistant cultivars and nine susceptible cultivars were evaluated at 15 SON-infested field sites and two noninfested sites during 1996 to 1998 in Minnesota. As expected, more nematodes developed on susceptible cultivars than on resistant cultivars. Egg density on susceptible cultivars increased by 1.9- to 10.6-fold during the growing season at 12 sites and did not change at the other three sites. Average egg density decreased over time for resistant cultivars at all sites, except where the initial egg density was low (less than or equal to 455 eggs per 100 cm(3) soil). Nematode reproduction factors (Rf = egg density at harvest/egg density at planting) for individual resistant and susceptible cultivars were highly consistent across the eight sites where initial SCN density was more than 1,000 eggs per 100 cm(3) soil. Resistance, however. varied among the cultivars, with the average Rf of individual resistant cultivars across the sites ranging from 0.3 to 1.7. Resistant cultivars produced an average yield of 3,082 kg/ha compared with 2,497 kg/ha by susceptible cultivars at eight of 10 sites where egg density at planting was greater than 700 eggs per 100 cm(3) soil. In contrast, no difference in yield was observed between resistant and susceptible cultivars at sites where egg density at planting was lower than 500 eggs per 100 cm3 soil. Yield differences between resistant and susceptible cultivars increased with increasing initial SCN egg density. In six fields infested with initial densities of more than 5,000 eggs per 100 cm(3) soil, resistant cultivars produced 28.4% (676 kg/ha) more yield on average than susceptible cultivars. Soybean yield increased when cultivars with increasing resistance to the SCN (lower Rf or females formed on roots) were grown in fields infested with SCN. Average relative yield (yield of a cultivar/average yield of all resistant cultivars at a site) of individual resistant cultivars across all SON-infested sites ranged from 0.76 to 1.10. Yield consistency of soybean cultivars was low among the different sites, indicating that many other factors affected yield. Our results suggest growing resistant cultivars is an effective method to manage SCN in Minnesota while minimizing yield loss due to SCN.
Article
Research must focus on management of diseases that cause extensive losses, especially when funds for research are limited. Knowledge of yield suppression caused by various soybean diseases is essential when prioritizing research. The objective of this project was to compile estimates of soybean yield suppression due to diseases in the USA from 1996 to 2007. The goal was to provide information to help funding agencies and scientists prioritize research objectives and budgets. Yield suppression due to individual diseases varied among years. Soybean cyst nematode suppressed USA soybean yield more from 1996 to 2007 than any other disease. Phytophthora root and stem rot ranked second among diseases that most suppressed yield seven of 12 years. Seedling diseases and charcoal rot also suppressed soybean yield during these years. Research and extension efforts must be expanded to provide more preventive and therapeutic disease management strategies for producers to reduce disease suppression of soybean yield. Accepted for publication 25 February 2009. Published 1 April 2009.
Article
Sudden death syndrome (SDS), caused by the fungal pathogen Fusarium virguliforme, causes significant yield reductions in soybean [Glycine max (L.) Merr.] in the United States. Appropriate recommendations to manage SDS for growers in Iowa and the Upper Midwest are limited. The research objective was to determine the response of SDS foliar disease incidence, severity, and yield to row spacing and seeding rate. In 2008 and 2009, at two Iowa locations, in fields with histories of SDS, SDS-susceptible and SDS-resistant cultivars were planted at 38- and 76-cm row spacing at seeding rates of 185,000, 309,000, and 432,000 seeds ha(-1) in plots infested with and without the pathogen. Sudden death syndrome incidence and severity were very low; however, infested plots had greater SDS disease incidence and severity than uninfested plots. A row spacing x infestation interaction indicated 7% greater yield in narrow rows (38 cm) than wide rows (76 cm) in uninfested plots, with no yield advantage to narrow rows in infested plots. Soil infestation reduced soybean seed mass (7%) in narrow rows, explaining the yield reduction for narrow rows with greater SDS. The two highest seeding rates had increased SDS incidence but yielded 9% greater than the lowest seeding rate. The susceptible cultivar had greater SDS incidence and severity and yielded 7% less than the resistant cultivar. This study indicates that in infested plots with greater SDS symptom expression, the yield advantage of narrow rows may be negated; therefore, cultivar selection is crucial when planting in narrow rows to maximize yield.
Article
Fusarium virguliforme causes sudden death syndrome (SDS) in soybean. The pathogen has never been isolated from diseased foliar tissues; therefore, one or more toxins have been considered to cause foliar SDS development. Cell-free F. virguliforme culture filtrates containing a toxin causes foliar SDS in soybean. A low-molecular-weight protein of approximately 13.5 kDa (FvTox1), purified from F. virguliforme culture filtrates, produces foliar SDS-like symptoms in cut soybean seedlings. Anti-FvTox1 monoclonal antibodies raised against the purified FvTox1 were used in isolating the FvTox1 gene. In the presence of light, recombinant FvTox1 protein expressed in an insect cell line resulted in chlorosis and necrosis in soybean leaf disks that are typical foliar SDS symptoms. SDS-susceptible but not the SDS-resistant soybean lines were sensitive to the baculovirus-expressed toxin. The requirement of light for foliar SDS-like symptom development indicates that FvTox1 induces foliar SDS in soybean, most likely through production of free radicals by interrupting photosynthesis.
Article
Sudden death syndrome, caused by Fusarium solani f. sp. glycines, has caused increased losses in soybean production in recent years. This study was done to identify potential sources of resistance to sudden death syndrome. Using a greenhouse screening procedure, 6,037 soybean plant introductions (PIs) were compared with a susceptible check, Great Lakes 3302, and two moderately resistant checks, PI 520.733 and PI 567.374, for resistance to sudden death syndrome. Only 57 PIs had foliar disease ratings that were not significantly different from PI 567.374 (P less than or equal to 0.05) 3 weeks after inoculation. Six PIs had lower ratings than PI 567.374 at 4 weeks after inoculation, while none had lower area under the disease progress curve (AUDPC) values. When comparing the PIs to PI 520.733, 209 PIs had foliar disease ratings not significantly different from PI 520.733 (P less than or equal to 0.05) 3 weeks after inoculation. Eight PIs had significantly lower disease severity ratings 4 weeks after inoculation, and 38 PIs had significantly lower AUDPC values than PI 520.733. Additionally, root lesion lengths were measured 4 weeks after inoculation and ranged from 25.2 to 41.5 mm for all the PIs; none of the entries had smaller lesion lengths than the susceptible check Great Lakes 3302. The correlation between lesion length and disease foliar severity rating was not significant. There also were no plant morphological characteristics (i.e., flower color or seed coat color) associated with higher sudden death syndrome foliar symptoms. Eighteen PIs previously identified as moderately resistant with differing agronomic traits were inoculated with five different isolates of Fusarium solani f. sp. glycines. Results indicated that resistance in these 18 PIs was effective against all five isolates of Fusarium solani f. sp. glycines. Isolate Mont-1 caused the greatest disease severity ratings. These PIs that exhibited low foliar severity ratings may provide new sources of resistance for the development of new sudden death syndrome-resistant lines and cultivars.
Article
The effects of alfalfa, red clover, and perennial ryegrass as cover crops on soybean cyst nematode (SCN) and soybean and corn yields were evaluated in Waseca, Lamberton, and Rosemount, MN. The cover crops were interseeded in soybean at 0 or 2 wks after planting soybean in 2002 and killed with herbicide before planting corn in 2003. As expected, SCN-susceptible soybean supported higher SCN population density than SCN-resistant soybean. Reduction of SCN population density by red clover (up to 40%) and alfalfa (up to 55%) was observed in some sampling occasions at Lamberton and Rosemount, probably due to reduced soybean growth, but the effect was inconsistent. No significant reduction of SCN population by the two crops was detected at Waseca. While perennial ryegrass did not affect SCN population density in most cases, up to 46% higher egg population densities were observed in the perennial ryegrass treatment as compared to the control at Waseca. SCN-resistant soybean produced higher yield than susceptible soybean at all sites. While alfalfa reduced soybean yield at Lamberton (up to 50%) and Rosemount (up to 11%), red clover and perennial ryegrass reduced soybean yield only at Lamberton (up to 38%) and Waseca (up to 34%), respectively. No difference in corn yield was observed at Waseca. At Lamberton, alfalfa and red clover planted at the time of planting soybean reduced corn yield in the following year 17 and 13%, respectively, and perennial ryegrass planted 2 wks after planting soybean reduced corn yield 13%. At Rosemount, significant reduction of corn yield was observed with red clover (15-21%) interseeded in SCN-susceptible soybean and with alfalfa (12%) and red clover (12%) interseeded in SCN-resistant soybean at the time of planting soybean. The results suggest that an even later planting date of cover crops in soybean may reduce yield loss due to competition and make these cover crops more appropriate for use in the soybean-corn rotation in Minnesota.
Article
The soybean cyst nematode (SCN), Heterodera glycines, is a major yield limiting pest of soybean (Glycine max). Current SCN management strategies include resistant soybean varieties and rotation with non-host crops. Increased adoption of the early soybean production system (ESPS) combined with a greater incidence of winter weeds from no-tillage practices may increase the population density of SCN during the noncrop period since several winter weeds and cover crops are hosts for SCN. A field experiment with a split-strip design was conducted over three years to evaluate whether SCN reproduced on weeds and cover crops during the noncrop period. Winter weeds and crimson clover roots were examined for females and cysts with eggs. The soil was sampled to determine if an increase in SCN egg population density occurred. We found no indication of SCN reproduction on winter weeds during the noncrop period or on the cover crop crimson clover. Accepted for publication 2 November 2006. Published 26 February 2007.
Article
Root diseases caused by soil-borne pathogens are often main constraints in legume crop production. Changes towards organic farming practices have recently contributed to an increase in legume cropping, mainly for nitrogen supply purposes, and these have raised concerns about unacceptable build-up of soil-borne pathogen inocula. This study aimed to evaluate the impact of frequent legume cropping on such inocula build-up, and had emphasis on Aphanomyces euteiches, an important pathogen causing pea root rot in Sweden. Field experiments with legume monocultures were established, and the effect of these monocultures on disease development and yields in subsequent pea, broad bean and snap bean was measured. Isolates of Aphanomyces spp., from several legumes, were tested for host ranges and characterised by means of morphological, biochemical and molecular methods. A survey of legume-specific soil-borne pathogens in fields under frequent legume cropping in northern Spain was also undertaken. Several legumes were found to be hosts for A. euteiches, and this pathogen was isolated from field-grown alfalfa, snap bean, pea, sweet clover and vetch. The Swedish isolates of A. euteiches were assigned two putative pathotypes, pea- and vetch-specific. Other species of Aphanomyces had a wide host range among legumes, but these did not induce disease symptoms. Sequencing of ITS1 - 5.8S - ITS2 rDNA region and RFLP of AT-rich DNA allowed appropriate delineation of these Aphanomyces spp. Monocultures of the tested legume crops affected the inoculum potential of A. euteiches differently. Pea, broad bean, snap bean, vetch and sweet clover were almost equally efficient in inoculum build-up and markedly affected subsequent pea and broad bean yields. Monocultures of alfalfa, birdsfoot trefoil, red, white, and Persian clover had lower impact on disease development and yields in subsequent crops. Thielaviopsis basicola and Rhizoctonia solani were the most prevalent pathogens in pea and snap bean fields in Spain and significantly affected yield. Climatic factors and soil properties favoured prevalence of these pathogens in Spain, whereas A. euteiches was most prevalent under Swedish conditions. It is concluded that intensive legume cropping will, on many soil types not be sustainable in the long-term due to the build-up of soil-borne pathogen inoculum.
Article
A total of 66 plants in 50 species were inoculated with eggs and juveniles of soybean cyst nematode, Heterodera glycines. Roots were stained and observed for penetration and development of the nematode. Twenty-six plants were not penetrated; twenty-three were penetrated, but there was no development of the nematode; eight were penetrated with some nematode development; two were penetrated and had considerable nematode development, but few nematodes, if any, matured; and seven were penetrated with many nematodes maturing. The penetration of nonhosts may imply some susceptibility and that populations eventually would build up on the penetrated plants. Plants not penetrated may be useful as rotation plants because no reproduction would occur.
Article
Experiments were established in field microplots to examine the association between Heterodera glycines and the blue form of Fusarium solani in sudden death syndrome of soybean (SDS). Foliar disease symptoms occurred on more plants per plot, appeared 3 to 7 days earlier, and were more severe on plants grown in plots infested with F. solani + H. glycines than on those inoculated with F. solani only. Yields were suppressed only in treatments that included the nematode. Numbers of H. glycines cysts and second-stage juveniles were significantly lower in plots infested with F. solani + H. glycines than with the nematode alone. Fusarium solani was able to infect cysts and eggs.
Article
The effects of the blue form of Fusarium solani, the causal agent of sudden death syndrome (SDS), on Heterodera glycines were examined in the greenhouse. Roots of soybean cv. Coker 156 were inoculated with either H. glycines alone or F. solani + H. glycines in combination. Population levels of H. glycines were reduced 47% in the presence of F. solani. Life-stage development of H. glycines increased 3% in 30 days in the presence of F. solani. Fusarium solani colonized epidermal and cortical cells adjacent to developing juveniles of H. glycines and the nematode-induced syncytia within the soybean root tissue. At 40 days after inoculation, F. solani was isolated from 37% of the cysts in soil recovered from the F. solani + H. glycines combination treatment. Fusarium solani significantly affected H. glycines population density, life-stage development, and succeeding populations.
Article
ABSTRACT The soybean cyst nematode, Heterodera glycines, and the fungus that causes sudden death syndrome (SDS) of soybean, Fusarium solani f. sp. glycines, frequently co-infest soybean (Glycine max) fields. The interactions between H. glycines and F. solani f. sp. glycines were investigated in factorial greenhouse experiments with different inoculum levels of both organisms on a soybean cultivar susceptible to both pathogens. Measured responses included root and shoot dry weights, H. glycines reproduction, area under the SDS disease progress curve, and fungal colonization of roots. Both H. glycines and F. solani f. sp. glycines reduced the growth of soybeans. Reproduction of H. glycines was suppressed by high inoculum levels but not by low levels of F. solani f. sp. glycines. The infection of soybean roots by H. glycines did not affect root colonization by the fungus, as determined by real-time polymerase chain reaction. Although both pathogens reduced the growth of soybeans, H. glycines did not increase SDS foliar symptoms, and statistical interactions between the two pathogens were seldom significant.
Root rot-like symptoms caused by grain-based inoculum substrates
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Cover crops shown to suppress soybean diseases. Resilient Agriculture Magazine
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Eastburn, D. 2014. Cover crops shown to suppress soybean diseases. Resilient Agriculture Magazine. August 2014:40.
On the soy bean nematode
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Ichinohe, M. 1952. On the soy bean nematode, Heterodera glycines n. sp., from Japan. Oyo-Dobutsugaku-Zasshi (Magazine of Applied Zoology) 17:1/2.
A standard greenhouse method for assessing soybean cyst nematode resistance in soybean: SCE08 (Standardized Cyst Evaluation
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Niblack, T.L., G.L. Tylka, P. Arelli, J. Bond, B. Diers, P. Donald, J. Faghihi, V.R. Ferris, K. Gallo, R.D. Heinz, H. Lopez-Nicora, R. Von Qualen, T. Welacky, and J. Wilcox. 2009. A standard greenhouse method for assessing soybean cyst nematode resistance in soybean: SCE08 (Standardized Cyst Evaluation 2008). Online. Plant Health Progress doi:10.1094/PHP-2009-0513-01-RV.
Annual Report Cover crop survey
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