Aaron Lorenz, Soybean breeder, Senyu Chen, Plant pathologist, Seth Naeve, Extension soybean agronomist, and Bruce Potter Extension IPM specialist
Background
 |
SCN-resistant soybean variety on left
and SCN-susceptible variety on right. |
The most common source of soybean cyst nematode (SCN) resistance in commercial soybean varieties adapted to Minnesota is PI 88788. Over 90% of the varieties entered into the 2021 UMN Variety trials carried this single source of SCN resistance. The PI 88788 resistance source provides good resistance to some races of SCN. Over time, however, the overuse of this resistance source has led to shifts in SCN populations to those that are able to overcome PI 88788 resistance. There has been increased interest in alternative sources of SCN resistance such as Peking and PI 89772. The commercial availability of these varieties adapted to Minnesota has gradually increased in recent years. However, little independent information is available on their actual resistance to SCN races known to overcome the PI 88788 source.
Methods
In the spring of 2021, we solicited seed of commercial varieties advertised to carry a non-88788 source of resistance and tested 15 submissions for resistance to Race 1 (HG Type 2.5.7) using a greenhouse bioassay with five replicates. Each container (one plant) was inoculated with 4000 SCN eggs. After 30 days a Female Index (FI) was calculated for each entry using Williams 82 as the susceptible check. The FI was calculated with the following formula: FI = (# of cysts on entry/# of cysts on Williams 82) x100. If the FI was <10%, an entry was considered resistant (R). If the FI was 10 – 30%, it was considered moderately resistant (MR). If the FI was 30-60%, it was considered moderately susceptible (MS), and greater than 60% susceptible (S).
Results
A total of 15 varieties were tested and a range of resistance responses was observed. The following table includes only those varieties that exhibited resistance or moderate resistance to Race 1 in our test. A specific variety may not be listed because either the seed provider did not consent to testing, or it did not exhibit resistance. Resistance to SCN is a product of large-effect single genes donated by certain resistance sources, in addition to many small-effects genes that may or may not be present in the variety, making resistance a complex genetic phenomenon. A variety with a resistance source in its ancestry does not necessarily make it completely resistant, and thus results from bioassays such as this one are helpful to ensure resistance is present. These results will assist producers in selecting varieties with independently verified resistance. If you are a seed provider and want your varieties to appear in this table, please inquire with Aaron Lorenz (
lore0149@umn.edu).
| Provider |
Variety |
Source of resistance |
Relative maturity |
Herbicide trait |
Female index |
Rating |
| Control* |
Peking |
|
|
|
0.3 |
R |
| Control |
PI 88788 |
|
|
|
35.8 |
MS |
| Syngenta / NK |
S23-G5X |
PI 89772 |
2.3 |
Xtend |
27.1 |
MR |
| Syngenta / NK |
S26-E3 |
Peking |
2.6 |
Enlist E3 |
18.3 |
MR |
| Mustang Seeds |
C-220N |
Peking |
2.2 |
Conv. |
2.5 |
R |
| Albert Lea Seed |
2340KN |
Peking |
2.3 |
Conv. |
2.0 |
R |
| Legend Seed |
LGS1452RX |
Peking |
1.4 |
Xtend |
1.5 |
R |
| Cornelius Seed |
CB26X78 |
Peking |
2.6 |
Xtend |
9.0 |
R |
| Federal Hybrids |
F2290N R2X |
Peking |
2.2 |
Xtend |
0.2 |
R |
| Stine |
25EB32 |
Peking |
2.5 |
Enlist E3 |
15.1 |
MR |
*Control varieties Peking and PI 88788 are two sources of SCN resistance, which were included in SCN race determination. The Female Indexes on these two varieties indicate that the SCN population can overcome the resistance in the varieties derived from PI 88788 but not the varieties with good level of Peking resistance. Seed is not available for these non-commercial varieties.
Products are mentioned for illustrative purposes only. Their inclusion does not mean endorsement and their absence does not imply disapproval.
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