Biosafety of hybrids between transgenic virus-resistant sugar beet and

swiss chard

Bartsch, et al.

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Objective of the Paper: To determine the potential invasion hazard of a GMO sugar beet crop that has a virus-resistant gene for Beet necrotic yellow vein virus (BNYVV)

-BNYVV leads to rhizomania, which is associated with loss in sucrose storage (field output) and storage capacity-Does not assess potential for gene flow or transgene escape (except for bolting time results) -Wild sea beet is the progenitor of all domesticated and cultivated beets and can cross with the cultivated sub-species-Introgression has been seen with cultivated beets and wild beets

-Manually crossed transgenic and non-transgenic cultivated beets with their relative, Swiss chard, to produce both trasngenic and non-transgenic hybrids

-Monitored biomass of various strains at 3 levels of competition and 2 infestation intensities of BNYVV

METHODS

• Do you agree with the following formula?

Risk = prob. of gene x potential hazard

flow or escape

The authors propose two scenarios for the escape of transgenes:

(1)via mating/gene flow between agricultural and wild plants and

(2) translocation of a GMO into the wild. What are some vectors for gene flow in

scenario 1? What are some ways a GMO may be translocated into the wild?

• Could there be a problem with the way the paper verified successful outcrossing (By spraying with a herbicide to detect the transfer and expression of the “bar” herbicide resistance gene)?

• Why does the paper measure biomasses at three different competition intensities?

• At the low infestation level, the non-transgenic hybrids outperformed their transgenic counterparts. How might you explain this? (see Fig. 1)

• The transgenics outperformed non-transgenic hydrids only at the high infestation level. What does this suggest about the selective advantage of this virus-resistance transgene?

• Transgenic hybrids show lower rates of bolting that non-transgenic hybrids and the parental chard (see Fig. 2). Do you think that the transgenes are involved?

• The authors used biomass as a proxy for fitness and reproductive potential. Even though they cite previous studies supporting biomass’s suitability as a proxy, do you think it is good enough?

• The virus is not seen in wild coastal sea beet populations but its presence in inland areas is unknown. Thus, would the location of the GMO crop effect the hazard potential of this transgene?

• Given the results of this study, would you authorize or deregulate the cultivation of these beet GMOs?

Reduced genetic variation and the success of an

invasive speciesTsuitsui, et al.

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• The Argentine ant, Linepithema humile, has invaded California and other sections of the country, displacing most native ants in these regions.

• The study collected ants from multiple sites in their native and introduced habitats. Ants were collected from individual nests, some of which were part of supercolonies, multiple nests showing no intraspecific aggression. Ants from different nests were then exposed to each other, and intraspecific aggression was measured.

• Genetic similarity between ant nests was measured using the percentage of alleles shared for specific microsatellites.

INTRODUCTION + METHODS

• The number of alleles in the introduced range is half the number in the native range, indicating the ants went through a genetic bottleneck.

• Both at small and large spacial scales, ant nests in the introduced range had greater genetic similarity and reduced intraspecific aggression.

• In both the native and introduced range, intraspecific aggression decreases with genetic similarity.

RESULTS

• General question: why do you think ants are such successful invaders?

• Can you think of any other species where reduced genetic variability in a population might confer a competitive advantage (even if temporary)?

• Notice anything strange in Fig. 2? Please discuss…

• Are there any factors besides the reduction in genetic variability that could be responsible for decreased intraspecific aggression in the ant’s introduced range?

• What do you think would happen if you exposed ants from the introduced range to ants from the native range?

• Do you agree with the fact that reduced genetic variability in the introduced ants is necessarily due to a bottleneck? Could it be due to something else?

• How might you introduce new alleles into introduced populations, as the author suggests?

• What are the risks?• Do the benefits outweigh the

risks, in your opinion?

• Do you agree with the statement in the paper that:

An increase in intraspecific competition within introduced populations should decrease the density of Argentine ants, thereby facilitating the recovery of invaded ecosystems

?