Tolerance of soybean varieties to white mold

As many of you know, the Iowa Soybean Promotion Board supports testing by the ISU Department of Plant Pathology of varieties tolerant to soybean white mold. Following preliminary experiments in 1995, we tested 63 entries from private and public sectors in the 1996 growing season.

Although results have been presented on various occasions, we continue to receive numerous requests from soybean producers for this information. Here is a portion of the data. Full results can be found on our World Wide Web site at this address: http://www.exnet.iastate.edu/Pages/plantpath/whitemold.html

The experiments were conducted at three locations and results at the following locations are presented: the Humboldt research plot in Humboldt County and the ISU Kanawha Research Farm in Hancock County. The Humboldt field has been naturally infested with soybean white mold for years and has the highest disease pressure among all testing sites. The Kanawha field was uniformly infested with a high sclerotia density in the fall of 1994 and again in the fall of 1995 using infested soybean debris. We also inoculated the plants with white mold culture at flowering time. Data of control plots showed that inoculation at flowering time was not effective and infections were from spores produced by sclerotia in the soil.

Table 1 and Table 2 (below) list the varieties whose tolerance was ranked in the top 30 at each location. Two susceptible varieties, A2242 and Williams 82, were grown as checks, and their results also are provided.

Tolerance of each variety was measured as the percentage of plants killed. The fewer plants killed for a variety, the higher the tolerance and the higher the variety's rank. The number of plants killed differed between locations because of varying disease pressure. The Humboldt site had higher disease pressure than the Kanawha site. For all data presented, there were four replications of each entry at each location. Maturity information is provided by individual companies or from 1995 ISU uniform yield tests.

To select a variety, compare the percentage of dead plants with that of the most susceptible varieties and look for consistency in tolerance rankings. Also, select varieties with higher yields. Keep in mind that these two locations had high disease pressure, which may not be present in your fields. In fields with mild disease pressure, varieties that did not receive high ranks in these two fields may do well.

Table 1. White mold resistance at the Humboldt plot

Company Variety Tolerance rank Plants killed (%) Yield estimate (bu/a) Maturity
Corsoy79 1 8.0 54.0 2.1
Dassel 2 9.3 48.9 1.1
Asgrow Seed Company A 2506 3 10.0 44.9 2.5
Custom Farm Seed CFS 181 4 10.0 49.8 1.8
Hy-Vigor Seeds 1150 5 11.3 55.6 1.5
Sands of Iowa, Inc. SOI 260 6 12.5 54.8 2.0
Mark Seed Company MRK 9519 7 13.0 59.4 2.0
Pioneer Hi-Bred Int'l, Inc. 9163 8 13.8 52.1 1.6
Midwest Seed Genetics, Inc. G 1885 9 14.3 56.5 1.9
Stine Seed Company 01526-84 10 16.3 58.7 -
Terra International, Inc. TS194 11 17.5 53.6 1.9
Northrup King Company S19-90 12 17.5 47.2 1.9
Kruger Seed Company K1990 13 18.8 58.5 1.9
AgriPro Seeds, Inc. AP 1876 14 18.8 52.7 1.8
Asgrow Seed Company A 1900 15 20.0 48.2 1.9
Gutwein and Sons, Inc. 7200 16 20.0 45.0 2.0
Parker 17 23.8 55.3 1.4
AgriPro Seeds, Inc. AP 1995 18 25.0 53.1 1.9
DeKalb Plant Genetics Company CX173 19 26.3 46.3 1.7
BSR101 20 27.5 39.9 1.9
Merschman Seeds ex01018-E 21 30.0 39.2 -
Latham Seed Company Latham 440 22 31.3 44.5 2.1
Dairyland Seed Company DSR-220STS 23 32.5 42.1 2.2
Sieben Hybrids, Inc. SS 273 24 32.5 38.4 2.7
Kenwood 25 33.8 43.0 2.1
Story Brand Seeds ST 203 26 35.0 42.0 1.9
Sands of Iowa, Inc. SOI 242 27 36.3 37.3 2.2
Custom Farm Seed CFS196 28 37.5 43.4 1.9
Dairyland Seed Company DSR-277 29 40.0 34.6 2.7
IA2007R 30 40.0 34.3 2.6
Asgrow Seed Company (Check) A 2242 60 70.0 26.3 2.2
(Check) Williams 82 62 78.8 14.1 -

Table 2. White mold resistance at the Kanawha plot

Company Variety Tolerance rank Plants killed (%) Yield (bu/ac)
Pioneer Hi-Bred Int'l, Inc. 9163 1 0.5 56.0
Dassel 2 1.6 34.0
Corsoy79 3 2.8 46.6
Northrup King Company S19-90 4 2.8 50.0
Custom Farm Seed CFS 181 5 3.4 52.3
Terra International, Inc. TS194 6 4.5 43.9
Asgrow Seed Company A 2506 7 6.1 50.0
Asgrow Seed Company A 1900 8 6.8 48.9
Hy-Vigor Seeds 1150 9 7.1 48.3
Parker 10 7.4 52.0
Midwest Seed Genetics G 1885 11 7.8 53.3
DeKalb Plant Genetics Company CX173 12 10.4 47.6
AgriPro Seeds, Inc. AP1876 13 13.1 41.5
Dairyland Seed Company DSR-277 14 13.9 45.6
Mark Seed Company MRK 9519 15 15.0 50.3
Gutwein & Sons, Inc. 7200 16 15.6 42.4
Latham Seed Company 720 Brand 17 15.8 47.8
Latham Seed Company 440 Brand 18 15.9 49.8
Sands of Iowa, Inc. SOI 260 19 16.3 48.1
Stine Seed Company 01526-84 20 16.5 45.5
Kruger Seed Company K1990 21 16.8 47.5
Mark Seed Company MRK 9227 22 16.8 48.3
Sands of Iowa, Inc. SOI 242 23 16.9 48.1
Stine Seed Company 1970 24 18.1 50.2
Marlin Wilkin and Sons MWS261 25 18.3 44.1
BSR101 26 18.4 40.0
Custom Farm Seed CFS196 27 18.6 45.0
Merschman Seeds ex01018-E 28 19.1 45.7
Bell 29 19.9 41.5
Lynks Seeds 5269 30 20.6 47.6
(Check) Williams82 59 53.8 23.2
Asgrow Seed Company (Check) A 2242 61 64.0 30.1

This article originally appeared on pages 191-192 of the IC-476(26) -- December 16, 1996 issue.

Updated 12/15/1996 - 1:00pm