2009 Uniform Soybean Tests Northern Region - Purdue University ...

DISEASE
Disease reactions are listed according to “Soybean Disease Survey Standards”, March 1960, unless otherwise specified.
Disease reaction is scored from 1 (no disease) to 5 (very severe), or in some cases as percent infected or simply as + (present)
or 0 (absent). Purple seed stain and seed mottling follow the disease severity class rating:
Disease severity class rating 1 2 3 4 5
Number of diseased seed in sample 0 1-3% 4-8% 9-19% 20-100%
An additional classification to describe the extent of seed coat mottling as M (mild), E (extensive), or S (severe), is included.
Pod and stem blight is rated as percent of infected seed on a four-week delayed (“d”) harvest sample. The location where the
test was made is identified in the column heading, and the letter “a” or “n” signifies artificial or natural infection. Clear-cut
and consistent reactions are given by letter instead of number: R = resistant, S = susceptible, I = intermediate, and H =
heterogeneous. Natural infection ratings are from agronomic tests in some instances and from special disease plantings in
others. Absence of symptoms under natural infection does not necessarily mean high resistance.
Abbreviation Disease Pathogen
BB Bacterial blight Pseudomonas syringa pv. glycinea
BBV Bud blight Tobacco ringspot virus
BP Bacterial pustule Xanthomonas campestris pv. phaseoli
BS Brown spot Septoria glycines
BSR Brown stem rot Phialophora gregata
BTS Bacterial tan spot Corynebacterium flaccumfaciens
CN Cyst nematode Heterodera glycines
CR Charcoal rot Macrophomina phaseolina
DM Downy mildew Peronospora manshurica
FE Frogeye leafspot Cercospora sojina
PM Powdery mildew Microsphaera diffusa
PR Phytophthora rot Phytophthora sojae
PS Purple stain Cercospora kikuchii
P&SB Pod & stem blight Phomopsis spp.
Pyd Pythium root rot Pythium debaryanum
Pyu Pythium root rot Pythium ultimum
RK Root knot nematode Meloidogyne spp.
RP Rhizoctonia root rot Rhizoctonia solani
SB Sclerotial blight Sclerotium rolfsii
NSC Northern Stem canker Diaporthe phaseolorum var. caulivora
SCL Sclerotinia stem rot Sclerotina sclerotiorum
SDS Sudden death syndrome Fusarium virguilforme, (F. solani f.sp. glycines)
SMV Soybean mosaic virus Soybean mosaic virus
TS Target spot Corynespora cassiicola
YMV Yellow mosaic virus Yellow mosaic virus
Rating for BB, BP, DM, FE, and PM are based on leaf symptoms; those for BSR on percent of plants with stem browning, or
percent of stem length browned.
Illinois Sudden Death Syndrome rating: Plots were scored by Southern Illinois University. All disease scores were
interpolated to the R 6.2 growth stage.
DX = SDS Disease index (DI x DS/9)
DI = SDS Disease Incidence (% of plants with visible leaf symptoms)
DS = SDS Disease Severity (1=mild chlorosis, 5=severe leaf scorch, 9=premature death of the plant)
Minnesota Iron Chlororis scores (IDC): Scores are the values on the average of 2 observations taken mid July, and early
August. Data was collected from Wilkin County, and Lake Lillian, Minnesota. Planting dates June 20, and June 22, 2008.
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