New Zealand Journal of Crop and Horticultural Science abstracts

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Transformation of potato (Solanum tuberosum) cultivars with a cry1Ac9 gene confers resistance to potato tuber moth (Phthorimaea operculella)

M. M. Davidson^1,2
M. F. G. Takla^1,2
J. M. E. Jacobs¹
R. C. Butler¹
S. D. Wratten²
A. J. Conner^1,2

¹New Zealand Institute for Crop & Food
   Research Limited
 Private Bag 4704
 Christchurch, New Zealand

²National Centre for Advanced Bio-Protection
   Technologies
 P.O. Box 84, Lincoln University
 Canterbury, New Zealand

Abstract  Eight potato (Solanum tuberosum) cultivars were transformed with a modified cry1Ac9 gene under the transcriptional control of the CaMV 35S promoter using Agrobacterium-mediated transformation with a nptII gene conferring kanamycin resistance as a selectable marker. Initially the transformation efficiency of two Agrobacterium strains (LBA4404 and AGL1) were compared using the potato cultivars ‘Iwa’ and ‘Ilam Hardy’. Both strains resulted in similar numbers of regenerated shoots, but there was a higher proportion of off-types among plants transformed using the AGL1 strain. Subsequently, the cultivars ‘Karaka’, ‘Pacific’, ‘Red Rascal’, ‘Rua’, ‘Russet Burbank’, and ‘White Delight’ were transformed with strain LBA4404. Putatively transformed lines with kanamycin resistance were assayed using multiplex polymerase chain reaction (PCR) with an endogenous potato actin as an internal control. From a total of 116 lines, 105 were confirmed as being PCR-positive for the nptII gene, of which 93 were also PCR-positive for the presence of the cry1Ac9 gene. The amount of Cry protein in all transgenic lines tested was less than 60 ng/g fresh leaf tissue. The growth of potato tuber moth (Phthorimaea operculella) larvae was inhibited by foliage from greenhouse-grown plants of 77 of the transgenic lines (P < 0.05). Fifty-five of these resistant transgenic lines were described as having a phenotypic appearance comparable to the corresponding parental cultivars, when grown in the greenhouse. Southern analysis on four highly resistant lines revealed they contained two to five copies of the cry1Ac9 gene. Several transgenic lines severely reduced larval growth while exhibiting a phenotype similar to their parent cultivar. These lines warrant further investigation in the field.

Keywords  Agrobacterium-mediated transformation; genetic engineering; potato; insect resistance; Bacillus thuringiensis; cry1Ac9; Phthorimaea operculella; potato tuber moth

H03081; Online publication date 17 March 2004; Received 10 September 2003; accepted 5 December 2003
New Zealand Journal of Crop and Horticultural Science, 2004, Vol. 32: 39-50
0014-0671/04/3201-0039 © The Royal Society of New Zealand 2004

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