Facilitating the recovery of phenotypically normal transgenic lines in clonal crops: a new strategy illustrated in potato |
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Authors: | Philippa J Barrell Anthony J Conner |
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Institution: | (1) New Zealand Institute for Plant & Food Research Limited, Private Bag 4704, Christchurch, 8140, New Zealand |
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Abstract: | Transgenic plants frequently exhibit altered phenotypes, unrelated to transgene expression, which are attributed to tissue
culture-induced variation and/or insertional mutagenesis. Distinguishing between these possibilities has been difficult in
clonal crops such as potato, due to their highly heterozygous background and the resulting inherent phenotypic variability
associated with segregation. This study reports the use of transgene integration as a molecular marker to trace the clonal
origin of single cells in tissue culture. Following transformation, multiple shoots have been regenerated from cell colonies
of potato (Solanum tuberosum L.) and Southern analysis used to confirm their derivation from a single transformed cell. Analysis of phenotypic variation
in field trials has demonstrated marked differences between these multiple regeneration events, the origin of which must have
occurred after T-DNA insertion, and consequently during the tissue culture phase. This result unequivocally demonstrates that
somaclonal variation occurs during tissue culture and independent of transgene insertion. Furthermore, the first shoots recovered
do not necessarily exhibit less somaclonal variation, since later regeneration events can give rise to plants that are more
phenotypically normal. Therefore, when developing transgenic lines for genetic improvement of clonal crops, multiple shoots
should be regenerated and evaluated from each transformation event to facilitate the recovery of phenotypically normal transgenic
lines. |
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