Variations in resistance against Phthorimaea operculella in wild potato tubers

Tuber resistance can contribute to current management strategies against the potato tuber moth, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae), in field and stored potatoes. Wild potatoes represent a potential source of novel resistance traits against the moth. We assessed resistance in three wild potato species, Solanum multiinterruptum Bitt., Solanum sparsipilum (Bitt.) Juz. & Buk., and Solanum wittmackii Bitt. against neonate and developing tuber moth larvae. All three species had high levels of resistance but accessions of S. sparsipilum and S. wittmackii were significantly more resistant. Resistance in S. multiinterruptum was generally concentrated in the tuber periderm, whereas in S. sparsipilum and S. wittmackii resistance was mainly cortex‐based. Unidentified cortex‐resistance factors in all three species reduced survival and increased larval and pupal development times, but had no apparent effects on the pupal weights of survivors. A high proportion of larvae abandoned or died within tubers of S. wittmackii, which has particularly high levels of unidentified cortex‐based defenses. Resistance decreased in S. multiinterruptum and S. sparsipilum as tubers sprouted but was more stable in S. wittmackii. Periderm‐based resistance was more stable than cortex‐based resistance in S. multiinterruptum during sprouting. In contrast, cortex‐based resistance was stable in tubers of S. wittmackii as these sprouted, and resistance may have increased on some older sprouting tubers. Solanum multiinterruptum and S. sparsipilum are proposed as potential sources of resistance against the potato tuber moth.     

Tuber production,dormancy and resistance against Phthorimaea operculella (Zeller) in wild potato species

The diversification of resistant potato varieties at a landscape level could slow adaptation by Phthorimaea operculella to potato resistance and promote sustainable crop protection. In this study, we assessed wild potato species as novel sources of foliage and tuber resistance against P. operculella. Tuber resistance was quantified for 136 and foliage resistance for 54 potato accessions representing 14 and nine potato species, respectively. Several accessions were highly resistant to moth damage in tubers and/or foliage. In particular, Solanum chiquidenum and Solanum sandemanii were highly resistant to damage in tubers. Several accessions of Solanum multiinterruptum and a small number of accessions of Solanum bukasovii, Solanum berthaultii, Solanum sparsipilum and Solanum wittmackii also had highly resistant tubers. Larval survival on foliage of S. bukasovii and S. chiquidenum was generally low. New resistance sources are listed, and insect performance on the plants is described with possible resistance mechanisms. The study also examined potential trade‐offs associated with resistance. Tuber resistance was negatively correlated with the number and weight of tubers produced per plant, but positively correlated with the length of dormancy across accessions, indicating that, although long dormancy is not a prerequisite for resistance, species and accessions with extended dormancy will have more resistant tubers. Tuber and foliage resistance were generally positively correlated across all accessions; however, among accessions from within a potato species, there were negative (S. berthaultii), positive (S. chiquidenum) and non‐significant (S. bukasovii) relations. These results indicate that, besides identifying novel resistance sources, an improved understanding of the mechanisms and inherent trade‐offs associated with tuber and foliage resistance will improve the efficiency of potato breeding programmes aimed at enhancing resistance against P. operculella.     

Periderm- and cortex-based resistance to tuber-feeding Phthorimaea operculella in two wild potato species

The trichome‐bearing wild potatoes Solanum berthaultii (Hawkes) and Solanum tarijense (Hawkes) (Solanaceae) have noted resistance to leaf‐feeding insect herbivores; however, little is known about their resistance to tuber‐feeding herbivores. This study evaluates resistance in tubers of these two species to attack by the potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae). Tubers from a range of accessions were presented to recently emerged neonate tuber moth larvae. Resistance to neonates varied between accessions and was generally higher in accessions of S. tarijense. The contribution to observed resistance of periderm vs. cortex factors was assessed by perforating tuber periderm in paired‐tuber experiments. Across species and accessions, an average of 62% of resistance was attributed to periderm‐related factors. All larvae entered tubers through the eyes. Unidentified cortex‐related factors affected larval development time and pupal weight. Sprouting compromised resistance by reducing the protective value of the periderm. The degree of sprouting also decreased larval development times and increased pupal weights in one of two accessions examined. These results demonstrate the potential of S. berthaultii and S. tarijense as sources of tuber‐resistance and identify accessions of both species with notably high periderm‐based protection. Levels of periderm resistance were not correlated to levels of cortex resistance and represent an independent resistance source compatible with the food value of crop potato.     

Temperature‐dependent phenology and growth potential of the Andean potato tuber moth,Symmetrischema tangolias (Gyen) (Lep., Gelechiidae)

The Andean potato tuber moth, Symmetrischema tangolias (Gyen) [Lepidoptera, Gelechiidae], is an economically important pest of potato (Solanum tuberosum L.) in the mid‐elevated Andean region and an invasive pest of partially global importance. Determination of the pest's population life table parameters is essential for understanding population development and growth under a variety of climates and as part of a pest risk analysis. The development, mortality and reproduction were studied in two pest populations (from Peru and Ecuador) in which cohorts of each life stage were exposed to different constant temperatures ranging from 10°C to 28°C. Using the Insect Life Cycle Modeling software, nonlinear equations were fitted to the data and an overall phenology model established to simulate life table parameters based on temperature. The temperature‐dependent development curve was statistically well described for eggs by Ratkowsky's model and for larvae and pupae by Taylor's model. Variability in development time among individuals independent of temperature was significantly described by a log‐logistic model. Temperature effects on immature mortality were described using different nonlinear models. Optimal temperature for survival was between 14° and 17°C. Temperature effects on adult senescence and oviposition time were described by simple exponential models; within‐group variability was described by a Weibull distribution function. Fecundity per female due to temperature followed a nonlinear model indicating maximum reproduction at ~17°C. The established model revealed good convergence with historical life tables established at fluctuating temperatures. The results confirm that S. tangolias is more adapted to cooler temperature than the common potato tuber moth, Phthorimaea operculella (Zeller). S. tangolias develops at temperatures within the range of 8–28.8°C with a maximum finite rate of population increase (=1.053) at 21°C. The established process‐based physiological model can be used globally to simulate life table parameters for S. tangolias based on temperature and should prove helpful for evaluating the potential establishment risk and in adjusting pest management programmes.     

Developing a biocontrol strategy to protect stored potato tubers from infestation with potato tuber moth species in the Andean region

Heavy infestations of stored potato (Solanum tuberosum L.) tubers by the two potato tuber moth species Symmetrischema tangolias (Gyen) and Tecia solanivora (Povolny) frequently occur in Andean potato‐growing regions of Ecuador. The aim of the study was to develop a biological control strategy for both species using powder formulations made of inert substances, Phthorimaea operculella (Zeller) granulovirus (PhopGV) and Bacillus thuringiensis Berliner subsp. kurstaki (Btk). The LC₅₀ of PhopGV on T. solanivora was 0.33 LE/L, and Btk caused 82.7% mortality at a concentration of 100 g/L in bioassays. The efficacy of talcum, kaolin, calcium carbonate and sand ranged between 76.2% and 98.7%. Calcium carbonate was highly effective to control both species; however, its efficacy was affected by the relative humidity and dropped to 55.4% at relative humidity of 100%. PhopGV at concentrations of five larvae equivalents (LE) per kg kaolin and Btk at a concentration of 60 g Btk/kg talcum caused 95.7% and 88.1% mortality of T. solanivora, respectively. In storage experiments, the efficacy of calcium carbonate alone and in combination with PhopGV (20 LE/kg) and Btk (15 g/kg) caused 95.0–99.8% mortality of T. solanivora in all treatments and reduced infestation on potato tubers by 83.6%–91.0%. In the case of S. tangolias, Btk significantly increased mortality to 96.5% compared with calcium carbonate alone and reduced tuber infestation by 83.4%. Storage of potato tubers in thin layers enhanced the efficacy of the calcium carbonate treatment compared with storage in bags. It was concluded that calcium carbonate alone seems to be appropriate for the control of T. solanivora, and an addition of 15 g Btk/kg would improve the control of S. tangolias. It is suggested to test these new formulations under on‐farm storage conditions.     

Use of the growth retardant tetcyclacis for potato tuber formation in vitro

The effects of the plant growth retardant tetcyclacis on in vitro tuber formation in potatoes was studied, using two different approaches: 1. tuber formation in various lines that did not or hardly form tubers under control conditions, and 2. tuber formation by the variety Bintje, which readily forms tubers. The ABA-deficient (droopy) lines of S. phureja hardly formed tubers without the addition of tetcyclacis. In the presence of this growth retardant tuberization was nearly 100%, within three weeks of in vitro culture, even in the absence of cytokinin. A series of somatic hybrids between S. tuberosum and S. brevidens, that did not form tubers in field and pot experiments, were tested. They all formed tubers in vitro in the presence of tetcyclacis. Stoloniferous shoots formed on single-node cuttings from in vitro grown Solanum tuberosum var Bintje plantlets were transferred to media containing a high level of sucrose. In the presence of tetcyclacis, tuber formation started after 4 days, reaching a maximum level of 80% at day 7. Tubers formed in the presence of tetcyclacis, accumulated starch and expressed several tuber-specific genes. These effects were fully antagonized by gibberellic acid. It is concluded that the growth retardant tetcyclacis is a potent tool in the study of tuber formation in potatoes.Abbreviations ABA abscisic acid - BAP benzylaminopurine - GA₃ gibberellic acid - STS silver thiosulphate - TET tetcyclacis     

Overcompensating plants: their expression of resistance traits and effects on herbivore preference and performance

Overcompensation is a plant tolerance response in which plants have higher fitness after herbivory than without damage. Although it has been demonstrated that plants are able to simultaneously express resistance and tolerance traits, it remains unclear whether overcompensating plants are also inducing resistance‐mediating secondary metabolite production and how herbivores perform on plants that overcompensate. Our previous work has shown that a potato variety [Solanum tuberosum L. cv. Pastusa Suprema (Solanaceae)] from Colombia can express overcompensatory responses to damage by larvae of the Guatemalan potato moth, Tecia solanivora Povolny (Lepidoptera: Gelechiidae). Here we investigated (1) whether potatoes that express overcompensatory responses also induce resistance traits and (2) how the previous damage affects Guatemalan potato moth preference and performance. Our results show that larval feeding not only systemically induces higher tuber biomass but also an increased production of resistance‐related compounds, such as phenolics and proteinase inhibitors. Pupal mass increased with increasing tuber size, whereas changes in tuber secondary metabolism did not correlate with any metric of larval performance. Oviposition preference did not change between induced and undamaged plants. Our data show that potato plants expressing overcompensatory responses also induce secondary compounds known to increase resistance against herbivores. However, the induced response was relatively small, reducing the opportunities for a negative effect on the herbivore. Hypotheses for why larvae perform better in larger tubers and are not affected by the secondary metabolism are discussed. From an ecological and agricultural point of view, our results suggest that the expression of overcompensatory traits could have positive effects on herbivore performance.     

Comparative compositional analysis of transgenic potato resistant to potato tuber moth (PTM) and its non-transformed counterpart

In this study, the compositions of transgenic potatoes (TPs) resistant to potato tuber moth (Phthorimaea operculella) were compared with those of its non-transgenic (NTP) counterparts. The light inducible promoter, phosphoenolpyruvate carboxylase led to the expression of Cry1Ab only in the leaves and light-treated tubers of the TPs. No significant differences were found in the moisture, ash, dry weight, total soluble protein, carbohydrate, starch, fiber, ascorbate, cations, anions, fatty acids, and glycoalkaloids contents of TP and NTP. Moreover, light treatment significantly affected the contents of ascorbate, acetate and nitrite anions, palmitic, stearic and linolenic fatty acids, α-haconine and α-solanine glycoalkaloids in TP and NTP tubers. While, significant differences were observed in the amino acid contents in light-treated tubers of TPs than the NTP ones. Although, light treatment in potato tubers resulted in marked metabolic changes, all the variations observed in the metabolites compositions were found to be within the desired reference ranges for potato plants. In conclusion, the results indicated that the TPs were substantially and nutritionally equivalent to the NTP counterparts.     

Use of seedling progeny tests for genetical studies as part of a potato (Solanum tuberosum subsp. tuberosum) breeding programme

A diallel set of crosses, including selfs and some reciprocal crosses, was made between 15 parents chosen for their male fertility from those included in a tetraploid potato (Solanum tuberosum subsp. tuberosum) breeding programme at the Scottish Crop Research Institute. Seedling progeny tests were used to evaluate the progenies for non-race-specific resistance to late blight (Phytophthora infestans) in both foliage and tubers, quantitative resistance to the white potato cystnematode (PCN) (Globodera pallida) and the commercial worth of their tubers as judged by breeders' visual preference. No reciprocal differences were found. Comparisons of the selfs and crosses revealed inbreeding depression for breeders' preference, which varied among the parents from negligible to severe, whilst there were also statistically significant differences for foliage and tuber blight, but not for PCN. When the selfs were omitted from the combining ability analyses, large differences in general combining ability (GCA) were found for all four traits, and smaller differences in specific combining ability for tuber blight and breeders' preference. The only statistically significant correlation between GCAs for different traits was a favourable one of r = 0.56 between foliage and tuber resistance to late blight. It was concluded that prospects were good for simultaneously improving all four traits by multitrait genotypic recurrent selection.     

Green-tissue-specific, C4-PEPC-promoter-driven expression of Cry1Ab makes transgenic potato plants resistant to tuber moth (Phthorimaeaoperculella, Zeller)

An important strategy for obtaining a safer transgenic plant may be the use of a spatial- or tissue-specific promoter, instead of a constitutive one. In this study, we have used a light-inducible maize PEPC promoter to regulate the cry1Ab gene, aiming to produce transgenic potatoes that are resistant to potato tuber moth (PTM) (Phthorimaea operculella, Zeller). Out of 60 regenerated lines having normal phenotypes, 55 lines were PCR-positive for both the cry1Ab and nptII genes. Southern analysis on three selected putative transgenic lines revealed that they have only a single intact copy of the cry1Ab gene. An investigation of the Cry1Ab protein in the leaves and light-exposed (LE) tubers of the transgenic lines demonstrated the presence of the protein in the foliage and green tubers but not in the light-not exposed (LNE) tubers. A bioassay analysis of excised leaves of nine randomly selected lines showed that eight lines had 100% PTM larval mortality. Confirming results were obtained in six selected lines using the whole plant bioassay in the greenhouse. LE transgenic tubers also exhibited 100% larval mortality; however, the levels of damage to the LNE transgenic tubers were high and statistically the same as those incurred by the non-transgenic ones. Based on the results, we believe that this spatial expression of Cry1Ab using the light-inducible PEPC promoter can control PTM infestation in the field and significantly reduce pollution transmission to storage potatoes.     

用马铃薯人工饲养马铃薯块茎蛾的方法

介绍一种马铃薯块茎蛾Phthorimaeaoperculella的室内人工饲养方法。在人工养虫室内用 1 0 %的蜂蜜水喂养成虫 ,用滤纸收集卵块 ,幼虫在薯块上饲养 ,化蛹于牛皮纸卷成的纸筒中 ,饲养结果发现马铃薯块茎蛾完成 1代大约需要 35～ 4 6d ,室内连续饲养块茎蛾 3代 ,卵的孵化率、幼虫化蛹率、成虫羽化率均在 90 %以上。     

Metabolic diversity in tuber tissues of native Chiloé potatoes and commercial cultivars of <Emphasis Type="Italic">Solanum tuberosum</Emphasis> ssp. <Emphasis Type="Italic">tuberosum</Emphasis> L.

Introduction

The native potatoes (Solanum tuberosum ssp. tuberosum L.) cultivated on Chiloé Island in southern Chile have great variability in terms of tuber shape, size, color and flavor. These traits have been preserved throughout generations due to the geographical position of Chiloé, as well as the different uses given by local farmers.

Objectives

The present study aimed to investigate the diversity of metabolites in skin and pulp tissues of eleven native accessions of potatoes from Chile, and evaluate the metabolite associations between tuber tissues.

Methods

For a deeper characterization of these accessions, we performed a comprehensive metabolic study in skin and pulp tissues of tubers, 3 months after harvesting. Specific targeted quantification of metabolites using 96 well microplates, and high-performance liquid chromatography combined with non-targeted metabolite profiling by gas chromatography time-of-flight mass spectrometry were used in this study.

Results

We observed differential levels of antioxidant activity and phenolic compounds between skin and pulp compared to a common commercial cultivar (Desireé). In addition, we uncovered considerable metabolite variability between different tuber tissues and between native potatoes. Network correlation analysis revealed different metabolite associations among tuber tissues that indicate distinct associations between primary metabolite and anthocyanin levels, and antioxidant activity in skin and pulp tissues. Moreover, multivariate analysis lead to the grouping of native and commercial cultivars based on metabolites from both skin and pulp tissues.

Conclusions

As well as providing important information to potato producers and breeding programs on the levels of health relevant phytochemicals and other abundant metabolites such as starch, proteins and amino acids, this study highlights the associations of different metabolites in tuber skins and pulp, indicating the need for distinct strategies for metabolic engineering in these tissues. Furthermore, this study shows that native Chilean potato accessions have great potential as a natural source of phytochemicals.

     

Mating frequency in dispersing potato tuber moth, Phthorimaea operculella, and its influence on the design of refugia to manage resistance in Bt transgenic crops

Mating of potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), was investigated in relation to the dispersal of males in laboratory and field trials. The effect of stimulating the flight of males to light sources in a large cage on their mating ability was estimated for three age groups, and compared with similar estimates for confined moths. Although the mating of males declined with ages of up to 15 days, simulated dispersal had no effect on subsequent mating when the males were paired with virgin females. The dispersal of male moths was also categorised by the initial flight activity of untethered moths to a light source. Scores for poor, moderate, and good flight provided a repeatable measure of initial male flight activity, but the degree of activity was not related to their subsequent mating ability. In the field, virgin female potato tuber moths were tethered at various distances from the edge of isolated potato crops and then dissected to determine their mating status. Female mating frequency averaged 75% at the crop margin, remained above 50% up to 200 m, and then declined to 19% at 360 m from the margin. Derivation of the mating probability for an individual male potato tuber moth confirmed earlier work by other researchers that has indicated a tendency for dispersal prior to mating, and that males retain their ability to mate as they disperse from a crop. The influence of dispersal and mating on gene flow between crops, and its potential effects on refuge size required to minimise the development of resistance to Bt transgenic potato crops was examined.     

Aspects of tuber resistance in hybrid potatoes to potato tuber worm

Tubers produced from crosses between the wild potato, Solanum berthaultii Hawkes (Solanaceae), and the cultivated species Solanum tuberosum L. (Solanaceae) are resistant to potato tuber worm (PTW), Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), infestation compared to those of the popular commercial North American cultivars Allegany, Atlantic, Chieftain, Katahdin, MaineChip, NorDonna, Norwis, Russet Norkotah, Snowden, and Yukon Gold. Given a choice between Atlantic and hybrid tubers, female PTW deposited ca. 50% fewer eggs on hybrid tubers than on those of Atlantic; larval survival and production of prepupae on hybrid tubers were reduced similarly. Time needed for neonates to penetrate eye buds was ca. 100 min greater on hybrid tubers compared to that on cv. Atlantic. Periderm of hybrid tubers is thicker than that of cv. Atlantic and may contribute to the delay in larval penetration of tubers and the success of initial establishment.     

Age-specific bioassays and fecundity of Phthorimaea operculella (Lepidoptera: Gelechiidae) reared on cry1Ac -transgenic potato plants

Variation in the susceptibility of lepidopterous pest larvae of different ages to transgenic crops and the potential for survivors to reproduce could have important consequences for the development of resistance in such pests. Experiments were undertaken in the laboratory to determine if larvae of the potato tuber moth, Phthorimaea operculella, of different ages (0 (< 1 day old), 3, 5, 7 days) varied in their susceptibility to cry1Ac9–transgenic potato (Solanum tuberosum) foliage grown in the glasshouse or field. The survival and fecundity of larvae reared on transgenic tubers was also determined in the laboratory. There were no apparent differences in susceptibility of larvae of different ages to transgenic foliage. Larvae fed glasshouse or field‐grown non‐transgenic foliage had significantly larger relative growth indices and more larvae pupated, than those fed transgenic foliage, regardless of larval age. Eggs from a laboratory colony were placed on transgenic or non‐transgenic tubers to measure survival and fecundity. Between 6% and 15% of eggs placed on transgenic tubers developed into pupae for three of the four transgenic potato lines tested. On one transgenic line, only six adults emerged from 1300 eggs. In contrast, between 71% and 97% of the eggs placed on non‐transgenic tubers developed into pupae. Male and female pupae from transgenic lines weighed less than those from non‐transgenic lines. The fecundity of females from two of four transgenic lines was lower than from the non‐transgenic parent cultivar. Although larvae of different ages did not exhibit any overall age‐dependent pattern of increasing or decreasing susceptibility to transgenic foliage of glasshouse or field‐grown plants, the ability of larvae to survive and reproduce on transgenic tubers suggests this pest has the ability to evolve resistance to the transgenic plants used in the present study.     

Oviposition deterrence of shoots and essential oils of Minthostachys spp. (Lamiaceae) against the potato tuber moth

Abstract:  The potato tuber moth is a noxious pest of potato in stores, where the use of repellent plants is an environmentally sound alternative to the application of chemical pesticides. We evaluated the protective effect of native Minthostachys species (Lamiaceae) against tuber infestation by the potato tuber moth in a rustic store in Cusco, Perú. We covered potato tubers with dried shoots of Minthostachys spicata and Minthostachys glabrescens and compared tuber damage with a control treatment of maize straw. We also conducted a no-choice oviposition bioassay in the laboratory, testing the oviposition deterrence of essential oils of M. spicata , M. glabrescens and Minthostachys mollis at natural concentrations. We recorded the number of eggs laid by mated moths on filter paper treated with essential oils of each of the three species and on two control treatments: hexane and untreated blank. Finally, we tested for differences in oviposition deterrence among five full-sib families of potato tuber moth raised under identical conditions. We found that dried, chopped leaves and flowers of Minthostachys species reduced the percentage of tuber damage in stores in comparison with the control (5% vs. 12%), but no difference in protection was found between species. Essential oils at natural concentrations deterred moth oviposition, reducing the number of eggs laid by about 80% compared with the control treatments; again, there were no significant differences between Minthostachys species. Finally, whereas we detected among-family variation in oviposition on filter papers treated with essential oils, no difference was found in the number of eggs laid on control substrates. Therefore, there was genetic variation for oviposition deterrence in the potato tuber moth and resistance to repellent plants might evolve thereafter.     

Enhanced fructose levels in field grown potato tubers expressing a thermostable glucose isomerase

A thermostable glucose isomerase was expressed in Solanum tuberosum Desirée using the tuber-specific granular-bound starch synthase promoter. The fructose content was substantially increased in microtubers, greenhouse grown tubers as well as tubers produced in field trials as compared with the controls. Furthermore, the tuber yield of field grown potatoes was enhanced by 30% in the transgenic lines (from 1.04 kg/plant in the wild type to 1.36 kg/plant in the transgenic lines).     

Resistance of potatoes transgenic for a cry1Ac9 gene, to Phthorimaea operculella (Lepidoptera: Gelechiidae) over field seasons and between plant organs

Stable performance of insect‐resistant transgenic plants across field seasons and between plant organs damaged by the insect pest is critical for management of this resistance in the field. To evaluate this, potato (Solanum tuberosum) lines transgenic for a cry1Ac9 gene with resistance to potato tuber moth (Phthorimaea operculella) were established in the field during the southern hemisphere summers of 1997/98, 1998/99 and 1999/00 as small field plots, each of 10 plants. Replicate plots of the non‐transgenic parent cultivars (at least one for every three independently derived transgenic lines) were planted randomly throughout the trials. Field‐grown foliage was challenged with larvae in the laboratory and a growth index (GI) was calculated for recovered larvae from each transgenic and non‐transgenic potato line. Larval growth on young and mature leaves, and on newly harvested or stored tubers was also measured in the laboratory. Foliage from the transgenic lines inhibited larval growth in all seasons tested. For both control and transgenic lines, larvae had slightly lower GIs when reared on mature leaves compared with young leaves, although the correlation between mean GI for young and mature transgenic leaves was high (r = 0.97). The correlation between the mean GIs of larvae on newly harvested tubers and on those stored for 5 months was also high (r = 1.0). However, the GIs of larvae on newly harvested transgenic tubers were larger than on transgenic tubers stored for 5 months. The relative growth indices (RGI = mean GI/number days before final weighing) of larvae reared on newly harvested tubers from transgenic lines were generally higher than those from young transgenic foliage, while the RGIs of larvae reared on non‐transgenic tubers were slightly lower than those fed non‐transgenic foliage. The correlation between mean RGIs of larvae fed tubers or foliage was 0.62. The transgenic potato lines exhibited stable resistance to larvae across field seasons, between affected plant organs, and between plant organs of different ages.