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Plant Pathology and Weed Science
Research Relevant to Indiana’s Seed Industry
Greg Shaner
Department of Botany and Plant Pathology
Purdue University
Title
Seed industry issues
 Many disease and weed control issues are the same for
farmers as for seed producers
 Higher value of seed crops
• Loss of yield or quality may have greater consequences
• Management options not economical for commodity producers may be
economical for seed producers
Title
2
Seed-related research
 Much of the research in Botany and Plant Pathology is
relevant to the seed industry
 This summary will focus on programs that have a more direct
bearing on production of seed
 Plant pathology
• Scott Abney, Larry Dunkle, Steve Goodwin, Guri Johal, Greg Shaner,
Andreas Westphal
 Weed Science
• Bill Johnson, Tom Bauman, Kevin Gibson
Title
3
Soybean sudden death syndrome
 Developed a method for evaluating root necrosis in the
greenhouse (Westphal)
 Looking at combined effects of SCN and Fusarium solani f.
sp. glycines on SDS (Westphal)
 Some evidence of soil suppressiveness of F. solani f. sp.
glycines after 3 yr of continuous soybean (Westphal)
 Field evaluation of resistance to SDS (Abney)
• 10 yr ago, 90% of varieties were very susceptible
• Now, about half have some resistance
• Most highly susceptible varieties have been eliminated
Title
4
Phytophthora rot
 Combining Rps1c or Rps1k with Rps3a or Rps8 (Abney)
 Evaluating some field isolates of Phytophthora sojae that
overcome Rps8 (Abney)
Title
5
Frogeye leaf spot
 Survey of isolates from throughout Indiana (Abney)
• None of these isolates overcomes Rcs3
 Foliar fungicide trials (Shaner)
• Several treatments suppressed frogeye leaf spot
Title
6
Soybean rust
 Extensive extension programs (Shaner and many others)
 Section 18 registrations of fungicides
 Foliar fungicide trials
• Evaluation of numerous products (Shaner)
• Farm-scale fungicide trials (Conley and Shaner)
 Sentinel plots
 Up-to-date advisories on USDA web site, and toll-free phone
line
Title
7
Gray leaf spot of corn
 Genetic variability in Cercospora zeae-maydis (Dunkle)
• Two distinct populations
• Resistance in corn expressed equally toward both
• A phytotoxin (cercosporin) is required for full development of lesions
Title
8
Northern corn leaf blight
 Limited surveys indicate that races 0 and 1 predominate in
Indiana
 Production of spores by Exserohilim turcicum involves a bluelight receptor (cryptochrome)
Title
9
Northern corn leaf spot (Johal)
 Basic studies on pathogenesis in Bipolaris zeicola and host
resistance in corn
 Lesion mimics
• 50 are known
• Deciphering molecular basis may shed light on nature of disease
resistance in corn
Title
10
Dwarfing gene in corn (Johal)
 Brachytic2 (br2)
 Gene reduces length of lower internodes
 Cells are smaller, but more numerous (2-3x)
 This adds greatly to stalk strength
Title
11
Fungicides on seed corn (Shaner)
 Several effective products
 Initial treatment must be early in disease development
 Benefit depends on susceptibility of inbred and environment
Title
12
Leaf blotch of wheat
 Several genes for resistance to Septoria tritici have been
mapped (Goodwin)
• Stb1, Stb2, Stb4, Stb8
• Most mapping is with microsatellites
» These are easy to work with--may lead to wider use in commercial
breeding programs
 Helping to develop molecular markers for a linkage block that
includes resistance to Stagonospora blotch, head blight, and
stem rust (Goodwin)
 Evaluation of fungicides for efficacy against leaf blotch
(Shaner)
Title
13
Fusarium head blight
 Development of weather-based risk model
• Can be used to make decisions about fungicide use
 Evaluation of fungicides and application timing for control
 Discovery and characterization of new sources of resistance
Title
14
Herbicide tolerance
 Popcorn (Bauman)
 Field corn (Bauman)
 Soybean (Johnson and Bauman)
• Includes studies of interactions of herbicides with fungicides and
insecticides
Title
15
Weed management (Johnson)
 Optimization and sustainability of weed management
systems to reduce glyphosate-resistant weed problems
• Resistant weeds pose a serious threat to continued success of
Roundup Ready technology
• Goal is to preserve efficacy of glyphosate resistance trait in soybean
 Re-evaluation of weed interference in corn grown with lower
nitrogen rates
 Weed management systems in Roundup Ready, Bt corn
• Optimization required to offset higher seed costs
Title
16
Vegetable weed management
(Gibson)
 Has use of glyphosate reduced weed seedbank numbers?
 If so, this may lead to improved, cheaper weed management
in vegetables that are rotated with field crops
Title
17