Rev 10/16/2023
Soybean Cyst Nematode
A member of the Schachtii group of Heterodera spp.
General Characteristics of the Schachtii Group of Heterodera
Cysts lemon-shaped Ambifenestrate Bullae well-developed Underbridge well-developed vulval slit long J2 incisures 4 Dicotyledonous hosts
(Handoo and Subbotin, 2018; Subbotin et al., 2010, Subbotin et al. 2023)
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:
Cysts on soybean rootlet.
Photograph by Charles Overstreet
Japan, China, Korea, Indonesia, South America, Soviet Union, Canada. As of 2019, it has been documented in 30 states within the U.S (Tylka and Marett, 2017)..
Very widespread in the United States (in 26 states, including North Carolina, Texas, Oklahoma; limited distribution in Arkansas; approximately 1/3 of soybean fields in North Carolina are infested).
The nematode appears to be able to survive and reproduces wherever there are host plants; it is able to survive low temperatures and other environmental stresses (Duan et al. 2009).
A-rated pest in California Nematode Pest Rating System.
During 2006-2009, soybean cyst nematode resulted in annual crop losses of US$1 billion annually in the US alone, making it the most imprortant pest of soybean (Koenning and Wrather, 2010; Liu et al., 2012).
Soybeans were planted in 36.2 million ha in the USA in 2017 (USDA, 2019). Soybean cyst nematode i9s considered the most important pathogen of soybean (Allen et al., 2017).
As they feed, the nematodes grow and molt three times, becoming larger with each molt. Mature males move out of the roots to find females, but the females remain attached to the root and continue to feed. Once the males leave the root they will not reenter the root or feed again.
Since nematodes in the Heteroderidae become sedentary from the late second stage onwards (except for the metamorphosis to males), the feeding site in the plant must be maintained in a condition favorable for perhaps five or six weeks to allow the nematode to fulfill its reproductive potential. In H. glycines, the Hg30C02 effector protein of Heterodera glycines may be involved in active suppression of host defenses (Hamamouch et al., 2012). As of 2013, some 70 proteins have been discovered in nematode secretions; many are new or unknown (Thomas Baum, pers. com.).
Hosts of the Schachtii group of Heterodera spp. are usually dicotyledonous plants. Heterodera glycines has numerous hosts, including soybean (Glycine max), dry bean, lupine, sweet clover, and chickweed.
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Ecophysiological Parameters:
Development and basic biology are similar to those of other cyst-nematodes.
Life cycle is 25 days at 23 C.
Males are present and mating occurs.
Male nematodes attracted to posterior region of female.
As the female matures her body swells and ruptures the root. She will mate with one or more males and begin producing eggs. Some eggs, 50 to 100, are produced outside of the female in an egg mass, but the majority of the eggs produced, 150 to 300, stay within the body of the female. The body cuticle "tans" after death of the female resulting in a brown, lemon-shaped cyst.
Four races have been reported (Golden, 1970); there may be a fifth race (or possibly up to 20 depending on host-range differentials that are used - see Riggs).
Races of Heterodera glycines, according to the race determination scheme proposed by Riggs and Schmitt (1988) (adapted from Niblack et al. 2006).
Race Number
Pickett
Peking
PI 88788
PI 90763
1
-
+
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Causes "yellow dwarf" disease in soybeans. Reduced yields.
Detection:
Fall sampling is often most convenient and will give the producer more time to make management decisions.
Regulatory: Rejection of infested plant material; federal quarantine was in effect in US from 1957 to 1972.
Resistant Cultivars: Hartwig (USDA soybean breeder) produced many resistant soybean varieties. The nematode is sexually reproducing and there appears to be considerable genotypic variability in field populations. Repeated use of resistant cultivars has led to selection of aggressive strains in many fields. Current recommendations are to rotate susceptible and resistant varieties with non-host crops to have a stabilizing selection effect on the nematode.
According to an Associated Press release in 2000, Midland Genetics Group, an alliance of six companies in Illinois, Iowa and Kansas, is the first to capitalize on a soybean plant first bred by Purdue University researchers that has proven resistant to more than 150 types of cyst nematode. Other companies are working to incorporate the new technology, called CystX, into their brands..
Much recent research was centered on the Hartwig soybean variety, which successfully resisted all versions of the nematodes but did not produce high yields. In 1994, Purdue University researchers finally bred the resistant capabilities of Hartwig into a higher-yield soybean variety. They spent two years testing it against every type of nematode they could before selling bought licensing rights to CystX.
In 2011 and 2012, resesarchers at Southern Illinois University Carbondale and the University of Missouri at Columbia identified and validated the gene at the Rhg4 (for resistance to Heterodera glycines 4) locus, a major driver in a soybean plant’s resistance to soybean cyst nematode. Soybean plants with multiple copies of a multi-gene block known as Rhg1 also show better resistance to soybean cyst nematode. Both projects allow researchers to focus on these gene structures -- Rhg1 and Rhg4 -- to help them develop soybean cyst nematode resistant soybean varieties.
The Rhg4 locus is a major quantitative trait locus contributing to resistance to H. glycines. Mutation analysis, gene silencing and transgenic complementation confirm that the gene confers resistance. The Rhg4 gene encodes a serine hydroxymethyltransferase (SHMT), an enzyme that is common in nature and found in both animal and plant kingdoms. The enzyme catalyzes conversions between serine and glycine and is essential for cellular carbon metabolism. Alleles of Rhg4 conferring resistance or susceptibility differ by two genetic polymorphisms that alter a key regulatory property of the enzyme. Soybean plants from a normally resistant variety, but with a mutated form of the SHMT gene, lost resistance to nematodes. When the SHMT gene was shut down by gene-silencing techniques, the normally resistant soybeans became susceptible. Transfer of the resistant form of the SHMT gene into normally susceptible soybeans conferred resistance to the nematode (Liu et al., 2012).
In general, resistance in soybeans is expressed as a hypersensitive response. Syncytia are initiated in both resistant and susceptible cultivars but degenerate in the resistant cultivars. They become necrotic and unable to support nematode development (Huang, 1998).
Biological Control: Riggs identified a fungus which he called ARF18 as an effective biological antagonist of cysts and eggs. Later the fungus was identified as a strain of Dactylella oviparasitica originally described by Stirling from soils around peach roots in California (Ole Becker, pers. com.)
Crop rotation: Rotation to non-host crops for 2 years is very effective (up to 90% reduction in population).
Nematicides: Fumigants are more effective than non-fumigants.
Australasian Plant Pathology Society Factsheets on Plant-parasitic Nematodes (Prepared by Dr. Graham R. Stirling)
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Allen, T.W. et al. 2017. Soybean yield loss estimatesdue to disease in the United States and Ontarion, Canada from 2010 to 2014. Plant Heal;the Prog.18:19-27.
Duan Y.X. Zheng, Y.N., Chen, L.J., Zhou, X.M., Wang, Y.Y. and Sun, J.S. 2009. Effects of abiotic environmental factorson soybean cyst nematode. Agr. Sci. China 8:317-325.
Hamamouch, N., Li, C., Hewezi, T., Baum, T.J., Mitchum, M.G., Hussey, R.S., Vodkin, L.O., Davis, E.L. 2012. The interaction of the novel Hg30C02 cyst nematode effector protein with a plant b-1,3-endoglucanase may suppress host defence to promote parasitism. Journal of Experimental Botany 63:3683-3695.
Handoo, Z.A., Subbotin, S.A. 2018. Taxonomy, identification and principal species. Chapter 15 in Perry, R.N. Moens, M., and Jones, J.T.(eds) Cyst Nematodes. CAB International.
Huang, J.S. 1998. Mechanisms of resistance. Pp353-368 in Sharma, S.B. (ed). The Cyst Nematodes. Kluwer, Dordrecht.
Kirby, H.W., J. Faghihi, G. Tylka, D. Jardine, G. Bird, W. Stienstra, P. Donald, T. Powers, B.D. Nelson, R. Mac Reidel, M.A. Draper, C. Grau. 2000. SCN Coalition. http://www.exnet.iastate.edu/Pages/plantpath/tylka/coalition/coalinfo.html.
Koenning, S.R., Wrather, J.A. 2010. Suppression of soybean yield potential in the continental United States from plant diseases estimated from 2006 to 2009. Plant Health Prog. http://dx.doi.org/10.1094/PHP-2010-1122-01-RS (2010).
Liu, S., Kandoth, P.K., Warren, S.D., Yeckel, G., Heinz, R.,Alden, J., Yang, C., Jamai, A., El-Mellouki, T.,. Juvale, P.S., Hill, J., Baum, T.J., Cianzio, S., Whitham, S.A., Korkin, D., Mitchum, M.G.,Meksem, K. 2012. A soybean cyst nematode resistance gene points to a new mechanism of plant resistance to pathogens. Nature doi:10.1038/nature11651.
Niblack TL, Lambert KN, Tylka GL (2006) A model plant pathogen from the kingdom animalia: Heterodera glycines, the soybean cyst nematode. Annu Rev Phytopathol 44:283–303.
Riggs RD, Schmitt DP (1988) Complete characterization of the race scheme for Heterodera glycines. J Nematol. 20:392–395.
Subbotin, S,A., Mundo-Ocampo, M., Baldwin, J.G. 2010. Systematics of Cyst Nematodes (Nematode: Heteroderinae). Nematology Monographs and Perspectives Volume 8B, D.J. Hunt and R.N. Perry (eds) Brill, Leiden, The Netherlands 512p
Subbotin, S.A., Roubtsova, T.V., Bostock, R.M., Maafi, Z.T., Chizhov, V.N., Palomares-Rius, J.E., Pablo Castillo, P. 2023. DNA barcoding, phylogeny and phylogeography of the cyst nematode species of the Schachtii group from the genus Heterodera (Tylenchida: Heteroderidae). Nematology (in press).
Tylka, G.L. and Marett, C.C. 2017. Known distribuition of of the soybean cyst nematode, Heterodera glycines, in the United States and Canada, 1954 to 2017. Plant Health Prog. 18:167-168,