Soybean Cyst Nematode Resistance:
soybean cyst nematode (SCN), Heterodera
glycines Ichinohe is a devastating pest of the soybean (Glycine
max L Merr.) worldwide. Yield losses in the U.S.A. due to SCN were
estimated at 213 million bushels in 1996 and 219 million bushels in
1997. This represents a loss in income to soybean farmers of
approximately $1.5 billion. This
is more than the soybean
loss from all other pests combined. SCN infection of soybean
causes various symptoms that may include chlorosis, root necrosis,
loss in seed yield and suppression of root and shoot growth. In
general, nematodes cause an estimated loss of approximately $100
billion per year worldwide.
Chemical control (soil fumigation) of SCN is not normally used because
the economical and environmental costs are prohibitive. Therefore,
cultural practices, such as crop rotation and the use of resistant
cultivars, are used to mitigate the damage of SCN. Use of naturally
occurring genes to control soybean cyst nematode and other pests is
generally more acceptable ecologically and economically than chemical
There are several known loci encoding resistance to SCN and specific
soybean genotypes have distinct responses to particular SCN races.
Soybean genotypes with different responses to SCN races serve as
differentials to identify SCN races. However, the contributions of
different loci to the resistance response at the molecular level is
not known. Furthermore,
the functions of genes involved in resistance are unknown.
Figure(1): Female Cyst Nematodes emerging from an
Life Cycle Nematode
Figure(2): Microscopic view of viable and
inviable cysts (brown) in infected soybean roots.
Figure(3): Infected soybean roots (left)
vs. uninfected roots (right).
We are taking two
approaches to enhancing the resistance of soybean to SCN:
Cloning of resistance genes by map
Identifying genes involved
in resistance by monitoring their expression patterns
display and microarrays.
T.E., B.F. Matthews, J.M. Weisemann and H.S. Beard. 1995.
Registration of recombinant inbred maplines of soybean germplasm. Probe 5:8.
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G.N. Ude and B.F. Matthews. 1996. Identification of molecular markers in soybean
using RFLP, RAPD, and AFLP DNA mapping techniques. Plant Molec. Biol. Report.
Ude, G, T.E. Devine, L.D. Kuykendall, B.F. Matthews, J. A. Saunders, W.
Kenworthy and J.J. Lin. 1998. RFLP Report: Genetic mapping of the soybean gene Rj4,
conditioning nodulation restriction with Bradyrhizobium
elkanii, a chlorosis-inducing microsymbiont, with molecular marker loci.
Symbiosis. 26: 101-110.
Cregan, P. J. Mudge, E.W. Fickus, L. Fredrick Marek, D. Danesh, R. Denny, R. C.
Shoemaker, B.F. Matthews, K. G. Lark and N. D. Young. 1999. Targeted isolation
of simple sequence repeat markers through the use of bacterial artificial
chromosomes. Theor. App. Genet. 98: 919-928