Trends in corn diseases
Jim Dodd
Professional Seed Research, Inc.
RACE T H. MAYDIS
Southern corn leaf blight 2011
Southern corn leaf blight 2011
Yellow leaf blight T cytoplasm
Yellow leaf blight W64A
H. CARBONUM? 1973
H. MAYDIS SPSORES
CARBONUM-MAYDIS POPULATION
EYESPOT W64 DISEASE
EYESPOT NATURAL RECENT
NORTHERN LEAF BLIGHT SUSCEPT
HT1 GENE
DOWNY MILDEW
CORN LETHAL NECROSIS 1978
GRAY LEAF SPOT
HEAD SMUT CANADA 1980
HEAD SMUT
Goss’ wilt
TRENDS
• PATHOGENS HAVE GENETIC VARIABILITY TOO
• PATHOGENS HAVE HUGE POPULATION SIZE
• POPULAR HYBRIDS HAVE SELECTIVE
VULNERABILITY
• NEED TO BE ALERT TO UNEXPECTED DISEASE
• CORN DIVERSITY IS PLENTIFUL AND CAN MEET
ANY DISEASE
Multigene resistance
• Most corn disease resistance is affected by 3-4
genes
• Resistance in hybrids usually the intermediate
between the two parents
• Majority of corn genotypes are moderately
resistance, intermediate or moderately
susceptible. Very few are ‘immune’ or
extreme susceptible.
DISEASE RESIST. RATINGS
• ATTEMPTING TO PREDICT DAMAGE WHEN
DISEASE PRESSURE IS GREAT
• DON’T TAKE AVERAGES- USE WORST RATING
• APPLY INOCULUM PRESSURE THAT ALLOWS
DISTINCTIONS
• DON’T MEASURE TOO FINE-ENVIRONMENT IS
TOO BIG A FACTOR
DISTRIBUTION OF RESISTANCE
2011 GEM ENTRIES
GOSS
NLB
SCLB
GRAY
SUSC.
INTERMED
RESIST
6.7%
28.3%
21.7%
23.3%
18.3%
21.7%
30.0%
45.0%
75.0%
50.0%
48.3%
31.7%
RESISTANT TO GOSS, SCLB, NLB AND GRAY
• (BR52051:N04-076-001/DKXL370:N11a20036-002-B)-B-B-001-B (BR52051:N04-076001/DKXL370:N11a20-036-002-B)-B-B-013-B
(BR52051:N04-076-001/DKXL370:N11a20036-002-B)-B-B-030-B DK888:N11(95)-B-027001-015-B DKXL370:S08c17b-B-046-B
FS8A(T):N1804-006-001-B-B-SIB KO679Y
SANM126:N1299b-B-067-B