, Volume 222, Issue 2, pp 372–385 | Cite as

Poor competitive fitness of transgenically mitigated tobacco in competition with the wild type in a replacement series

  • Hani Al-Ahmad
  • Shmuel Galili
  • Jonathan GresselEmail author
Original Article


Transgenic crops can interbreed with other crop cultivars or with related weeds, increasing the potential of the hybrid progeny for competition. To prevent generating competitive hybrids, we previously tested tobacco (Nicotiana tabacum L.) as a model for validating the transgenic mitigation (TM) concept using tandem constructs where a gene of choice is linked to mitigating genes that are positive or neutral to the crop, but deleterious to a recipient under competition. Here, we examine the efficacy of the TM concept at various ratios of transgenically mitigated tobacco in competition with the wild type tobacco in an ecological replacement series. The dwarf/herbicide-resistant TM transgenic plants cultivated alone under self-competition grew well and formed many more flowers than the tall wild type, which is an indication of greater reproductivity. In contrast to the wild type, TM flowering was almost completely suppressed in mixed cultures at most TM/wild type ratios up to 75% transgenic, as the TM plants were extremely unfit to reproduce. In addition, homozygous TM progeny had an even lower competitive fitness against the wild type than hemizygous/homozygous TM segregants. Thus, the TM technology was effective in reducing the risk of transgene establishment of intraspecific transgenic hybrids at different competitive levels, at the close spacing typical of weed populations.


Competitive fitness Gene flow Nicotiana Replacement series Tandem constructs Transgenic mitigation 



Acetohydroxy acid synthase


Gibberellic acid insensitive


Transgenic mitigation/Transgenically mitigated


Wild type



Shiri Gerson, Alexandra Savitsky, Judith Karmi, and Ziv Hanan provided excellent technical assistance. We thank Dr. Dvora Aviv for her advice and help in tobacco transformation and tissue culture techniques. Dr. Roy Chaleff, American Cyanamid Company kindly provided plasmid pAC456; and Drs. Donald Richards and Nick Harberd, Department of Molecular Genetics, John Innes Centre, UK kindly provided plasmid pλ g/SK+ with the Δgai gene. This research was supported by the Levin Foundation, INCO–DC contract no. ERB IC18 CT 98 0391, and a bequest from Israel and Diana Safer.


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Hani Al-Ahmad
    • 1
  • Shmuel Galili
    • 2
  • Jonathan Gressel
    • 1
    Email author
  1. 1.Plant SciencesWeizmann Institute of ScienceRehovotIsrael
  2. 2.Agronomy and Natural Resources Department, Agricultural Research OrganizationThe Volcani CenterBet DaganIsrael

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