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Use of the Roundup Ready TM Trait to Estimate Selfing in Hand Crosses of Alfalfa Mark McCaslin and Stephen Temple Forage Genetics International
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Background Alfalfa is predominately cross pollinated % selfing is difficult to determine without simple and effective genetic markers Transgenic traits offer unique advantages in studying alfalfa genetics and reproductive biology. –Cross vs self pollination –Pollen flow studies
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Advantages of the Roundup Ready Trait CP4 gene inherited as a single gene dominant trait Easily identified phenotype –Efficient high-throughput screening Multiple transgenic events available with event- specific PCR primers. PromoterCP4 GeneTPTerminator Event specific PCR
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Experimental Design Two populations of plants (~50 plants each) –Pop B – simplex plants containing transgenic event B (Bxxx). –Pop D – simplex plants containing transgenic event D (Dxxx). Non-emasculated hand crosses were made in greenhouse Pop D (female parent) x Pop B
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Experimental Design Seed harvested from Pop D plants Progeny were sprayed with Roundup RR progeny were tested with event- specific PCR to identify the RR genotype –BD dihomogenic –D event only –B event only
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Results 74.4% of the progeny were tolerant to Roundup (75% expected). Genotypes of the RR progeny were established with event-specific PCR and frequency of each genotype was compared to theoretical value. Genotype# plants% actual% expected BD dihomo206830.533.3 B only192328.433.3 D only277640.933.3
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Discussion Increased frequency of D event only progeny and decreased frequency of B event only and BD dihomogenic is likely due to unintentional selfing during hand crossing. Data suggests ~10% selfing in this cross Similar results from other crosses over multiple years, locations and genetic backgrounds.
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Discussion Other pollination related experiments planned or in process: –Cross vs self-fertility with leafcutter bees in commercial seed production setting. –Pollen flow studies with honeybees
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