Recovery of phenotypically normal transgenic potato plants is facilitated by regenerating multiple lines from transformation events: field validation using a cry9Aa2 gene conferring insect resistance

ABSTRACT

A modified cry9Aa2 gene under the transcriptional control of the CaMV 35S promoter was transferred to four potato cultivars (‘Iwa’, ‘Karaka’, ‘Pacific’ and ‘Red Rascal’) using Agrobacterium-mediated gene transfer. Field plots were established for 170 independently regenerated transgenic lines derived from 113 transformation events. Phenotypic changes such as stunted plants, reduced vigour and/or leaf puckering, were observed in 29% of these lines. Foliage from the remaining 117 lines inhibited larval growth of potato tuber moth (Phthorimaea operculella Zeller) compared with non-transgenic controls. A high correlation was observed between greenhouse- and field-grown foliage for insect resistance using a detached leaf bioassay. Independently regenerated lines recovered from the same transformation event exhibited similar insect resistance. However, these lines derived from the same transformed cell differed markedly in phenotypic appearance and tuber yield. The first shoot regenerated from each transformation event was equivalent to the non-transgenic control for yield traits in only eight transformation events. A further 19 transformation events exhibited agronomic performance equivalent to the non-transgenic control when the second or subsequent regenerated shoots were evaluated. In clonal crops, multiple shoots from each transformation event should be independently assessed to ensure recovery of high-performing transgenic lines.

KEYWORDS:

• cry9Aa2 gene
• insect resistance
• Phthorimaea operculella
• potato tuber moth
• CaMV 35S promoter
• Solanum tuberosum
• somaclonal variation
• transgenic potatoes
• field testing

Acknowledgements

We thank Jill Reader, Melanie Davidson, Michael Takla, Dharshini Ganeshan and Nic Jacobs for assistance with the planting, maintenance and harvest of the field trials; Ruth Butler for contributing to the statistical analysis; and Philippa Barrell, Mary Christey, Ruth Butler and Ruth Williams for comments on earlier drafts of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was funded by the New Zealand Foundation for Research, Science and Technology [contract C02X0204] and The Potato Industry Research and Development Grants Committee of the New Zealand Vegetable and Potato Growers Federation.