UNIVERSITE DE BOURGOGNE THÈSE Yongbo LIU - Université de ...

ARTICLE 4
SIMULATED INS ECT-RESISTANT VE RSUS S USCEPTIBLE
BRASSICA JUNCEA INTRA-POPULATION COMPETITION
Yongbo LIU, Wei WEI, KePing MA and Henri DARMENCY
Summary
• F ew s tudies ha ve f ocused on t he e ffect of relative f itness on popul ation d ynamics w hen
transgenes are transferred from a crop to its wild relatives, independent from the interspecific
hybridization cost.
• We clipped leaves to simulate the performance of transgenic, insect-resistant plants of wild
Brassica juncea in pure stands and in mixtures with non-clipped plants in field experiments
over two field seasons.
• The total vegetative and reproductive production of mixed populations was the same as that
of pur e popul ations. T he c ombined e ffects of d efoliation a nd r esource availability on t he
performance of B. juncea were additive. Healthy plants held a competitive advantage when in
competition with damaged plants, and the relative advantage increased as the percentage of
healthy plants increased. Investment in sexual reproduction did not differ between healthy and
damaged plants, but it did decrease with decreased intra-population competition or decreased
resource availability.
• These results suggest that if a transgene for insect-tolerance were to invade wild populations,
high he rbivory and l ow resource a vailability would f acilitate t he s pread of r esistant pl ants.
However, a population shift from predominantly susceptible to predominantly insect-resistant
individuals w ould not r esult i n di fferent d emographic ki netics, i .e. t he species w ould not
become more invasive.
Key w ords: Brassica j uncea, c ompetition, i nvasion, popul ation pr oductivity, s imulated
herbivory
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