Confinement of transgenes – seeds and volunteers L. M. Hall M. A. McPherson University of Alberta/Alberta Agriculture, Food and Rural Development McPherson MA, Good AG, Topinka AKC, Hall LM. 2004. Theoretical hybridization potential of transgenic safflower (Carthamus tinctorius L.) with weedy relatives in the New World. Can. J. Plant. Sci. 84: 923- 934. Section Carthamus Section Atractylis C. palaestinus C. persicus C. creticus C. oxyacanthus C. tinctorius C. lanatus (safflower) C. gypsicola ? n = 12 C. turkestanicus Uncertain placement n = 22, 32 C. curdicus ? C. nitidus n = 12 Carthamus-Carduncellus complex Section Odonthagnathis Femeniasia balearca ? C. tenuis C. divaricatus C. leucocaulos Lamottea caeruleus C. glaucus Phonus arborescens C. boissieri ? C. dentatus Phonus rhiphaeus n = 12 n = 10, 11 Spatial and temporal gene flow Pollen Seed Seed Handling Volunteer Crops Adventitious Introgression presence Admixture Weedy or Admixture Relatives conventional invasive crops Safflower Seeds z 80,000 ha in the USA z <1,000 ha in Canada z Used as birdseed z (no food use in Canada) z Oilseed in USA z Glufosinate resistant z PMP platform Seed dispersal z Can lead to volunteer populations in natural areas or in the same field z Wild safflower has been reported from California, Illinois Kansas New Mexico, Ohio and Utah but not Canada z The longevity or extent of these populations has not been documents z Safflower is shatter resistant, but harvest losses have been reported to be 5% Seed dispersal z Seed on the surface can be removed and dispersed by small mammals and birds z 500 plants/m2 spread on the surface prior to freeze z <10% remaining in the spring Seedlings germinating 100 80 60 WT 40 PMP 20 0 0 102030 Intervals Germination Predation Expire Soil Seed Bank Seed dormancy Viability of safflower seed enclosed in seed packages, surface and 2 cm depth 1 1 PMP 0.8 WT 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 0 01234567 01234567 Extraction Time Extraction Time Seed longevity in the seed bank – Little innate dormancy – Limited secondary dormancy z Depends upon – Predation – When the seeds enter the seed bank – Depth of burial – Soil moisture (threshold) – Soil temperature (determines time/rate) – Light Safflower volunteers Safflower as a volunteer crop Herbicide Control of Safflower in Canola Control Glyphosate Sethoxydim/Ethametsulfuron Imazamox/Imazethapyr Glufosinate 0 20406080100 Control at 4 weeks (%) No Herbicidal Control Control by Glyphosate Herbicide Control of Safflower in Barley Fenoxyprop/Bromoxynil/MCPA Fenoxyprop/2,4-D Tralkoxydim/Bromoxynil/MCPA Control 0 20406080100 Control at 4 weeks (%) Summary z Shattering resistance reduces the amount of seed deposited in the field z Harvest losses do occur, (ca. 5% Smith 1996) z Seed has limited/ no innate dormancy z Seed predation limits viable seed left on soil surface but may lead to off site dispersal z Soil incorporated seed germinates rapidly z Control of volunteer in the year following safflower crop is essential Summary (2) z Volunteers are readily controlled by appropriate herbicides, including glyphosate, auxinic herbicides but not glufosinate or ALS inhibitors z Competitive crops limits success of any volunteers which are not controlled z Short season crops are usually harvested prior to seed maturity, limiting admixture.