Understanding resistance to cabbage seedpod weevil in yellow mustard x canola hybrids Sanford Eigenbrode Plant, Soil and Entomological Sciences University of Idaho, Moscow, Idaho Oilseed Conference 12 Feb 2009

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) Ceutorhynchus obstrictus CSPW

Long term goal – oilseed crops resistant to the CSPW

Mustard Condiment yellow mustard, Sinapis alba High glucosinolate concentrations Resistant or tolerant to most insects Sinapis alba A ‘non-host’ for CSPW

Mustard Two approaches Breed for oilseed quality mustard that retains resistance Introduce resistance from yellow condiment mustard into B. napus using interspecific crossing

Mustard Two approaches Breed for oilseed quality mustard that retains resistance Introduce resistance from yellow condiment mustard into B. napus using interspecific crossing

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

Glucosinolate S. alba UI B. napus ‘Cyclone’ 3-Butenyl Pentenyl OH 3-Butenyl OH-Benzyl Total Parental Species Glucosinolate Profiles (μmol/g)

Hybrid Glucosinolate Profile µmol/g R R R R R = ‘Resistant’ to CSPW = eggs 17% to 25% of control Ross et al. 2003

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 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  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 After 1 day of oviposition: dissect under a light microscope Count feeding punctures and eggs. Cabbage Seedpod Weevil Eggs

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)

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 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 Ongoing project on host relationships of Ceutorhynchus cardaria (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 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

Special notes Project initiated by Joe McCaffrey (UI Entomology) Long experience and expertise includes CSPW and other pests of oilseed Brassica crops 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

Questions ?