Estimation of virulence
type and level of soybean cyst nematode field populations in
response to resistant cultivars
J. W. Zheng1,2 and S. Y. Chen1*
1Southern Research and
Outreach Center, University of Minnesota, Waseca, MN 56093;
Biotechnology, College of Agriculture and Biotechnology,
Zhejiang University, Hangzhou 310029, P. R. China.
*Corresponding author. E-mail:
+1507 837 5621. Fax: +1 507 835 3622.
Accepted 16 March, 2011
The use of resistant
cultivars is the most common practice in managing the
soybean cyst nematode (SCN), Heterodera glycines.
Currently, most commercial SCN-resistant soybean cultivars
were developed from a single source of resistance, plant
introduction (PI) 88788. The effect of crop sequences
including rotations of SCN-susceptible soybean ‘sturdy’ with
SCN-resistant soybean ‘freeborn’ carrying resistance derived
from PI 88788, soybean ‘Pioneer 9234’ carrying resistance
derived from PI 548402 (peking), and nonhost corn was
studied at two field sites in southern Minnesota, the United
States. Parasitic ability of SCN measured as a female
index (FI) on PI 88788 and freeborn increased with the
number of years freeborn was planted. After more than 5
years of freeborn, either in monoculture or rotation with
other soybean cultivars and corn, the SCN population changed
from the original race 3 (HG type 0 or 7) to race 1 (HG type
2.7 or 2.5.7). After 10 years of freeborn, the changed
nematode population reproduced freely on the once resistant
> 60). There was no selection pressure from the use
of PI 88788-resistance on SCN populations that can overcome
peking resistance. Planting 3 or fewer years of Pioneer 9234
had no noticeable effect on the virulence phenotype of the
SCN population. This study suggests that more cultivars from
resistance sources other than PI 88788 are urgently needed
for effective management of the nematode in Minnesota and
other regions in the world.
Key words: Heterodera glycines, HG
type, host-parasite relationship, race, soybean cyst
nematode, virulence phenotype.