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Understanding resistance to cabbage seedpod weevil in yellow mustard x canola hybrids

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Understanding resistance to cabbage seedpod weevil in yellow mustard x canola hybrids. Sanford Eigenbrode Plant , Soil and Entomological Sciences University of Idaho, Moscow, 83844- 2339 [email protected] Idaho Oilseed Conference 12 Feb 2009. Insect pests in canola.

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slide1

Understanding resistance to cabbage seedpod weevil in yellow mustard xcanola hybrids

Sanford Eigenbrode

Plant, Soil and Entomological Sciences

University of Idaho, Moscow, 83844-2339

[email protected]

Idaho Oilseed Conference

12 Feb 2009

insect pests in canola
Insect pests in canola
  • 10% - 40% yield reductions from all insects.
  • One persistent insect problem is the cabbage seed pod weevil (CSPW)
  • A crucifer specialist
  • Can reduce rapeseed yields up to 35% (McCaffrey et al., 1986)

Ceutorhynchusobstrictus

CSPW

mustard
Mustard
  • Condiment yellow mustard, Sinapis alba
  • High glucosinolate concentrations
  • Resistant or tolerant to most insects

Sinapis alba

A ‘non-host’ for CSPW

mustard6
Mustard

Two approaches

  • Breed for oilseed quality mustard that retains resistance
  • Introduce resistance from yellow condiment mustard into B. napususing interspecific crossing
mustard7
Mustard

Two approaches

  • Breed for oilseed quality mustard that retains resistance
  • Introduce resistance from yellow condiment mustard into B. napususing interspecific crossing
slide8

Canola x yellow mustardhybrids

cross-pollination between S. alba and B. napus followed by a combination of ovule culture and embryo rescue (Brown et al., 1997)

X

slide9

Parental Species

Glucosinolate Profiles (μmol/g)

slide10

Hybrid Glucosinolate Profile

R = ‘Resistant’ to CSPW

= eggs 17% to 25% of control

S

R

R

R

S = ‘Susceptible’ to CSPW

= eggs 40 to 70% of control

µmol/g

S

Ross et al. 2003

R

S

conclusions from prior work
Conclusions from prior work
  • Resistance varies widely in S. alba x B. napus hybrids
  • The best lines tested so far are not as resistant as the resistant parent, S. alba
  • The mechanism is unknown, but appears to be unrelated to glucosinolate profiles
objectives of this project
Objectives of this project
  • Screen additional interspecific hybrids, seeking additional hybrids resistant to oviposition by CSPW
  • Having identified resistant hybrids
    • Employ detailed behavioral bioassay to ascertain weevil responses
    • Conduct a wider survey of metabolites potentially responsible for resistance
    • Characterize pod morphology
screen canister choice tests
Screen: Canister Choice Tests
  • 25 entries:
    • 5 parents + 20 hybrids
  • choice test:
    • each entry against Cyclone
    • excised ripe pods placed in cages with 1 ovipositing female weevil.
    • Count punctures, oviposition holes, eggs deposited (by dissection)
    • N = 10

Canisters for insect choice tests

canister choice tests
Canister Choice Tests

After 1 day ofoviposition:

dissect under a light microscope

Count feeding punctures and eggs.

Cabbage Seedpod Weevil Eggs

observations
Observations
  • Selected lines, based on resistance and phenotype will be tested in no-choice setting
  • Individual ovipositing female weevils will be observed continuously for 1 hour
  • Behavior on susceptible and resistant types compared for number of events and time spent engaged in:
    • Pod exploration
    • Preliminary feeding
    • Egg cavity formation
    • Turning
    • Ovipositing
    • Retracting
    • Pod brushing

Following Kozlowski et al. (1983)

observations16
Observations
  • Resistant and susceptible reactions will be compared statistically
  • Noldus ‘Observer’ behavioral software
  • Key behaviors correlated with different types of resistance will be noted
  • N = 40 individual weevils x 8 selected lines
characterization
Characterization
  • Measure pod size, toughness, hairiness and correlate these features with observed resistance.
  • Conduct a broad metabolic screen of the most resistant pod tissues to identify chemical profiles other than glucosinolates that could confer resistance.
chemical characterization
Chemical characterization
  • Ongoing project on host relationships of Ceutorhynchuscardaria(hoary cress biological control)
  • Employs metabolic profiling (≈ 200 metabolites included).
  • Samples of most promising S. alba x B. napus hybrids can be included.
years 1 and 2
Years 1 and 2
  • Year 1
    • bioassay, focus on the initial screening using choice tests (using live collected weevils)
    • characterize pod material morphologically and chemically (winter)
  • Year 2
    • bioassay, focus on direct observational studies (live collected weevils)
    • Select lines for additional development
slide20

Special notes

  • Project initiated by Joe McCaffrey (UI Entomology)
  • Long experience and expertise includes CSPW and other pests of oilseed Brassicacrops
  • My credentials for this project
  • M.S. and Ph.D. on aspects of Brassica entomology
  • Background in Host Plant Resistance to insects
  • Expertise in chemical ecology, plant defenses, glucosinolates
  • Veteran collaborator with Jack Brown
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