Physiological strains of soybean cyst nematode (SCN) were first reported by Ross (1962). Later a new biotype was observed in Arkansas (Riggs et al ., 1968). The SCN pathotypes then known were classified into four races based on their ability to reproduce on a set of soybean differentials (Golden et al. , 1970) .
Anand, S. C. and Brar, G. S.
"Research Notes: New races of cyst nematode,"
Soybean Genetics Newsletter: Vol. 8
, Article 28.
Available at: http://lib.dr.iastate.edu/soybeangenetics/vol8/iss1/28