Ransom Pollen Drift in Wheat

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Published on October 4, 2007

Author: The_Rock

Source: authorstream.com

Gene Flow Through Pollen Drift: A Scientific Perspective:  Gene Flow Through Pollen Drift: A Scientific Perspective Joel Ransom Extension Agronomist – Cereal Crops Slide2:  Gene Flow Movement of gametes (i.e. pollen), zygotes (seeds) and plants from one place to another and their incorporation into the gene pool at the new locality (Slatkin, 1987). Occurs naturally via Seed dispersal Pollen movement Slide3:  For the purpose of this presentation, focus is on the transfer of genes, mainly transgenes, from one crop variety to another. Pollen drift does not equal gene flow (fertilization must occur) Can include gene movement to related species (i.e. wheat and jointed goatgrass). Renewed interest in pollen flow:  Renewed interest in pollen flow Development of transgenic wheat Adverse reception of trangenics in some markets Segregation of trangenics from non-trangenics important Pollen drift data can be used to develop policies and procedures for maintaining segregation (IP programs) How does gene flow via pollen drift occur?:  How does gene flow via pollen drift occur? Some biology: Pollen is produced in anthers Pollen is released by anthers – “anthesis” Fertilization requires viable pollen to attach to a receptive stigma and the successful transfer to DNA to the ovule. Factors affecting gene flow:  Factors affecting gene flow Crop Corn – Cross pollinated (wind), isolations of 660’ Canola - Cross pollinated (wind and insects), isolations of > 1,320’ Barley – Self pollinated (flowers in the boot), isolations of 5’ Soybean – Self pollinated, isolations of 5 ft’ Factors affecting gene flow:  Factors affecting gene flow Distance between plants Temperature Humidity Wind Insects Variety Receptivity of the stigma ‘Nick’ (synchrony of flowering) Pollen viability Gene Flow in Wheat – Current State of Knowledge:  Gene Flow in Wheat – Current State of Knowledge Review of pollen movement studies Review of information from fertilization studies Isolation distances Varietal effects Facts about wheat pollen:  Facts about wheat pollen Relatively heavy Viable for 2 to 20 minutes 2,000 to 4,000 pollen grains per flower How far can wheat pollen move?:  How far can wheat pollen move? Adapted from Khan et al, 1973 (Kansas) Pollination of a male sterile :  Pollination of a male sterile Adapted from Khan et al, 1973 Pollination of a male sterile :  Pollination of a male sterile Adapted from J. Miller et al., 1975. 7 locations in ND Y=0 36 ft 41 ft 34 ft Summary on pollen movement:  Summary on pollen movement Viable wheat pollen can move > 150 ft Zero tolerance will be unworkable Based on male sterile plants, cross pollination risk greatest in first 20 ft of isolation from source Fertilization success dependant on pollen concentration Slide14:  Summary of studies quantifying cross fertilization in traditional wheat Effect of variety and year on out-crossing in Kansas, HRWW:  Effect of variety and year on out-crossing in Kansas, HRWW Adapted from Martin, 1990 Effect of variety and year on out-crossing (92-93), HRSW, Canada:  Effect of variety and year on out-crossing (92-93), HRSW, Canada Adapted from Hucl, 1996 Effect of isolation distance on out-crossing of four Canadian wheat cultivars, 1995 :  Effect of isolation distance on out-crossing of four Canadian wheat cultivars, 1995 Adapted from Hucl & Matus-Cadiz, 2001 Out-crossed seed number by distance:  Out-crossed seed number by distance Oslo Katepwa Percent Percent Seed/bu Seed/bu Distance (ft) Factors conferring varietal differences in cross-pollination propensity:  Factors conferring varietal differences in cross-pollination propensity Glume opening Extrusion of anthers Duration of opening Open spikelets vs dense spikes What are the practical implications of these data?:  What are the practical implications of these data? Gene flow between transgenic and non-transgenic varieties will depend on Distance from pollen source Variety Environment Isolation distance for < 0.01% most varieties = 10 ft Promiscuous varieties = 80 ft Management Recommendations for non-GMO IP programs:  Management Recommendations for non-GMO IP programs Maintain isolations of 90 ft (conservative based on the most promiscuous cultivar) Use border rows to “flood” field with non-GMO pollen Use different planting dates and maturity types than GMO neighbors Use pure seed and clean equipment Conclusions:  Conclusions Wheat pollen can move significant distances (>200 ft) Tolerance levels of transgenes are needed; zero tolerance will not be workable Gene flow is dependant on environment, varieties grown and isolation distance Data on out-crossing potential of ND varieties is needed for refining segregation strategies Conclusions:  Conclusions Gene flow through pollen drift is low in wheat and IP programs for non-GMO cultivars should not be difficult Use isolation distances > 90 ft and follow other practices that reduce the risk of cross pollination Avoiding physical mixtures will be key Seedstocks and soybeans 2 of 4 soybean fields in Iowa GMO in seed

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