Plant Pathology and Weed Science Research Relevant to Indiana

1
Plant Pathology and Weed ScienceResearch
Relevant to Indianas Seed Industry

• Greg Shaner
• Department of Botany and Plant Pathology
• Purdue University

2
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

3
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

4
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

5
Phytophthora rot

• Combining Rps1c or Rps1k with Rps3a or Rps8
  (Abney)
• Evaluating some field isolates of Phytophthora
  sojae that overcome Rps8 (Abney)

6
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

7
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

8
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

9
Northern corn leaf blight

• Limited surveys indicate that races 0 and 1
  predominate in Indiana
• Production of spores by Exserohilim turcicum
  involves a blue-light receptor (cryptochrome)

10
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

11
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

12
Fungicides on seed corn (Shaner)

• Several effective products
• Initial treatment must be early in disease
  development
• Benefit depends on susceptibility of inbred and
  environment

13
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)

14
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

15
Herbicide tolerance

• Popcorn (Bauman)
• Field corn (Bauman)
• Soybean (Johnson and Bauman)
• Includes studies of interactions of herbicides
  with fungicides and insecticides

16
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

17
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