Transgenic potato plants with enhanced resistance to the peach-potato aphid Myzus persicae

Potato plants (Solanum tuberosum) cv. Desiree were transformed with the genes encoding the proteins bean chitinase (BCH), snowdrop lectin (GNA) and wheat a-amylase inhibitor (WAI) under the control of the constitutive CaMV 35S promoter. Transgenic plants with detectable levels of foreign RNA were then selected for further characterisation with respect to protein expression levels by immunodot blot analysis using polyclonal antibodies raised against the respective protein. With the exception of WAI, plants expressing high levels of RNA, expressed correspondingly high levels of the foreign protein (1.5-2.0% of the total soluble protein). Although high levels of WAI mRNA were detected in some of the transformants, the protein could not be detected. On the bases of expression levels, two lines, designated PWG6#85 (transformed with the double construct WAI/GNA) and PBG6#47 (transformed with the double construct BCH/GNA), were selected for testing in aphid trials for enhanced levels of resistance. Both transgenic lines had a marked and significant effect on fecundity. The number of nymphs produced per female per day peaked at 4.1 and 4.2 for lines PBG6#47 and PWG6#85 respectively, compared to a value of 5.4 on control plants. Total nymphal production was also significantly lower on either of the transgenic lines compared to control plants (P<0.001) with the differences between the lines being only just significant (P= 0.058). On line PBG6#47 there was a delay in nymphal production of 1.6 days, representing a delay of 15%, and on line PWG6#85 this was 3.2 days, representing a delay of ca. 30%. The intrinsic rates of increase (r(m)) were also significantly lower on both of the transgenic lines in comparison to that on control plants (P<0.001), however the differences between the lines were not significant. The potential of using such genes as part of an over all strategy for the control of aphid populations is discussed.