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Soybean Varieties with non-88788 SCN Resistance Adapted to Minnesota

Aaron Lorenz1, Senyu Chen2, Seth Naeve1,3 and Bruce Potter3

1Department of Agronomy and Plant Genetics, 2Department of Plant Pathology, 3University of Minnesota Extension

The most common source of SCN resistance in commercial soybean varieties adapted to Minnesota is PI 88788. Over 90% of the varieties entered into the 2022 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 able to overcome PI88788 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.

Study methods

Starting in the spring of 2021, we have annually solicited seed of commercial varieties advertised to carry a non-88788 source of resistance and tested 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

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).

Table 1. Soybean varieties in trial that exhibited resistance or moderate resistance to SCN Race 1.

Year
entered
ProviderVarietySource of
resistance
Relative
maturity
Herbicide traitFemale indexRating
 Control*Peking   0.3R
        
        
 Control*PI 88788   35.8MS
2021Syngenta / NKS23-G5XPI 897722.3Xtend27.1MR
2021Syngenta / NKS26-E3Peking2.6Enlist E318.3MR
2021Mustang SeedsC-220NPeking2.2Conv.2.5R
2021Albert Lea Seed2340KNPeking2.3Conv.2.0R
2021Legend SeedLGS1452RXPeking1.4Xtend1.5R
2021Cornelius SeedCB26X78Peking2.6Xtend9.0R
2021Federal HybridsF2290N R2XPeking2.2Xtend0.2R
2021Stine25EB62Peking2.5Enlist E315.1MR
2022Channel2020R2XPeking2.0Xtend0.1R
2022Stine21EE62Peking2.1Enlist E30.8R
2022FederalF1720N RXFPeking1.7Xtend Flex0.6R

* 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.

Source : umn.edu

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