Progeny Plants Research Articles

Autosegregation of enzyme loci in agamospermous progenies of triploid plants of sugar beet (Beta vulgaris L.)

The ratios of the phenotypic classes of glucosephosphate isomerase (GP12) and malate dehydrogenase (MDH1 and MDH2) were studied in agamospermous progenies of triploid sugar beet plants. The ratio of the phenotypic classes of these enzymes corresponds to the calculations based on the assumption of polyteny of chromosomes carrying alleles of the enzyme loci accompanied by the loss of extra copies of the alleles in the first division of a cell entering embryogenesis. An increase in the gene dosage due to polyteny leads to the appearance in the progeny with a definite frequency of alleles that were absent in the original parental plant. The notions of meiotic autosegregation and mitotic autosegregation characteristic of meiotic and mitotic agamospermy are introduced, as well as the term locus polygenotype characterizing not only the allelic composition and the number of chromosomes, but also the number of chromatids carrying alleles of the marker locus in the cell before its entry into embryogenesis.

Characterization of development and artemisinin biosynthesis in self-pollinated Artemisia annua plants

Artemisia annua L. is the only natural resource that produces artemisinin (Qinghaosu), an endoperoxide sesquiterpene lactone used in the artemisinin-combination therapy of malaria. The cross-hybridization properties of A. annua do not favor studying artemisinin biosynthesis. To overcome this problem, in this study, we report on selection of self-pollinated A. annua plants and characterize their development and artemisinin biosynthesis. Self-pollinated F2 plants selected were grown under optimized growth conditions, consisting of long day (16 h of light) and short day (9 h of light) exposures in a phytotron. The life cycles of these plants were approximately 3 months long, and final heights of 30-35 cm were achieved. The leaves on the main stems exhibited obvious morphological changes, from indented single leaves to odd, pinnately compound leaves. Leaves and flowers formed glandular and T-shaped trichomes on their surfaces. The glandular trichome densities increased from the bottom to the top leaves. High performance liquid chromatography-mass spectrometry-based metabolic profiling analyses showed that leaves, flowers, and young seedlings of F2 plants produced artemisinin. In leaves, the levels of artemisinin increased from the bottom to the top of the plants, showing a positive correlation to the density increase of glandular trichomes. RT-PCR analysis showed that progeny of self-pollinated plants expressed the amorpha-4, 11-diene synthase (ADS) and cytochrome P450 monooxygenase 71 AV1 (CYP71AV1) genes, which are involved in artemisinin biosynthesis in leaves and flowers. The use of self-pollinated A. annua plants will be a valuable approach to the study of artemisinin biosynthesis.

Production of transgenic rice new germplasm with strong resistance against two isolations of Rice stripe virus by RNA interference

Rice stripe disease, with the pathogen Rice stripe virus (RSV), is one of the most widespread and severe virus diseases. Cultivating a resistant breed is an essential and efficient method in preventing rice stripe disease. Following RNA interference (RNAi) theory, we constructed three RNAi binary vectors based on coat protein (CP), special-disease protein (SP) and chimeric CP/SP gene sequence. Transgenic lines of rice cv. Yujing6 were generated through Agrobacterium-mediated transformation. We inoculated T1 generation plants from each line derived from CP/SP, CP, and SP transgenic rice plants with two RSV isolates from Shandong Province and Jiangsu Province using viruliferous vector insects. In these resistance assays, chimeric CP/SP RNAi lines showed stronger resistance against two isolates than CP or SP single RNAi lines. Stable integration and expression of RNAi transgenes were confirmed by Southern and northern blot analysis of independent transgenic lines. In the resistant transgenic lines, lower levels of transgene transcripts and specific short interference RNAs were observed relative to the susceptible transgenic plant, which showed that virus resistance was increased by RNAi. Genetic analysis demonstrated that transgene and virus resistance was stably inherited in the T2 progeny plants.

The RNA-mediated silencing of one of the Pin genes in allohexaploid wheat simultaneously decreases the expression of the other, and increases grain hardness

The RNAi-mediated silencing of Pina and Pinb, the two genes responsible for the grain texture of allohexaploid wheat, was induced and analysed in two wheat cultivars, Kontesa and Torka. A characterization of the two genes in non-transgenic plants revealed that Pinb carries a point mutation, designated Pinb-D1c in both cultivars. This mutation does not influence transcript abundance or protein content. Two silencing cassettes of the hpRNA type were constructed and used for stable transformation via Agrobacterium. In total, 43 transgenic lines representing the two cultivars were obtained, transformed with the silencing cassettes for Pina or for Pinb or co-transformed with both cassettes. The relative transcript levels of the two genes in the same progeny plant were found to be similar, independent of the silencing cassette used. The reduction in the Pina and Pinb transcript levels in the segregating T(1) progeny of Kontesa and Torka transformed with one of the silencing cassettes exceeded 80%. Co-transformation with the silencing cassettes for both genes resulted in a reduction of over 91% of Pina and Pinb transcripts in some segregating T(1) progeny of Kontesa. The silencing was transmitted to the T(4) kernel generation of the T(3) lines. A significant reduction or lack of both puroindoline proteins in the silenced lines correlated with an essential increase in grain hardness. The discussion covers some new insights into the function of the Pin genes, including the simultaneous silencing of both, independent of the siRNA signal.

An siRNA pathway prevents transgenerational retrotransposition in plants subjected to stress

Eukaryotic genomes consist to a significant extent of retrotransposons that are suppressed by host epigenetic mechanisms, preventing their uncontrolled propagation. However, it is not clear how this is achieved. Here we show that in Arabidopsis seedlings subjected to heat stress, a copia-type retrotransposon named ONSEN (Japanese 'hot spring') not only became transcriptionally active but also synthesized extrachromosomal DNA copies. Heat-induced ONSEN accumulation was stimulated in mutants impaired in the biogenesis of small interfering RNAs (siRNAs); however, there was no evidence of transposition occurring in vegetative tissues. After stress, both ONSEN transcripts and extrachromosomal DNA gradually decayed and were no longer detected after 20-30 days. Surprisingly, a high frequency of new ONSEN insertions was observed in the progeny of stressed plants deficient in siRNAs. Insertion patterns revealed that this transgenerational retrotransposition occurred during flower development and before gametogenesis. Therefore in plants with compromised siRNA biogenesis, memory of stress was maintained throughout development, priming ONSEN to transpose during differentiation of generative organs. Retrotransposition was not observed in the progeny of wild-type plants subjected to stress or in non-stressed mutant controls, pointing to a crucial role of the siRNA pathway in restricting retrotransposition triggered by environmental stress. Finally, we found that natural and experimentally induced variants in ONSEN insertions confer heat responsiveness to nearby genes, and therefore mobility bursts may generate novel, stress-responsive regulatory gene networks.

Efficient sweet pepper transformation mediated by the BABY BOOM transcription factor

Pepper (Capsicum L.) is a nutritionally and economically important crop that is cultivated throughout the world as a vegetable, condiment, and food additive. Genetic transformation using Agrobacterium tumefaciens (agrobacterium) is a powerful biotechnology tool that could be used in pepper to develop community-based functional genomics resources and to introduce important agronomic traits. However, pepper is considered to be highly recalcitrant for agrobacterium-mediated transformation, and current transformation protocols are either inefficient, cumbersome or highly genotype dependent. The main bottleneck in pepper transformation is the inability to generate cells that are competent for both regeneration and transformation. Here, we report that ectopic expression of the Brassica napus BABY BOOM AP2/ERF transcription factor overcomes this bottleneck and can be used to efficiently regenerate transgenic plants from otherwise recalcitrant sweet pepper (C. annuum) varieties. Transient activation of BABY BOOM in the progeny plants induced prolific cell regeneration and was used to produce a large number of somatic embryos that could be converted readily to seedlings. The data highlight the utility of combining biotechnology and classical plant tissue culture approaches to develop an efficient transformation and regeneration system for a highly recalcitrant vegetable crop.Electronic supplementary materialThe online version of this article (doi:10.1007/s00299-011-1018-x) contains supplementary material, which is available to authorized users.

Biolistic transformation of cotton (Gossypium hirsutum L.) with the phyA gene from Aspergillus ficuum

Transgenic cotton with an increased level of phytase activity was generated from cotton (Gossypium hirsutum L.) cv. ND94-7 by subjecting shoot-apex explants to particle bombardment. These tissues were transformed with plasmid pC-KSA2300 carrying a selectable marker (for kanamycin) and a target gene (phytase, or phyA, from Aspergillus ficuum). Primary plants were regenerated in a medium containing 75 mg l−1 kanamycin. Of 1,534 shoot apices, 52 (3.4%) survived on this selection medium. Southern and Northern blot analyses confirmed that phyA was stably integrated and expressed in those primary transgenics. The progenies of the primary transgenic plants were found to have a 3.1- to 3.2-fold increase in root extracellular phytase activity, resulting in improved phosphorus (P) nutrition. Growth also was enhanced when they were supplied with phytate, and their P content was equivalent to that of wildtype plants supplied with inorganic phosphate. These results demonstrate that the expression of phyA in cotton plants improves their ability to utilize organic P in response to a deficiency.

Analyses of inheritance patterns and consistent expression of sporamin and chitinase PjChi-1 genes in Brassica napus

With 6 figures and 2 tables Abstract Stable and consistent expression of foreign genes in serial propagation is a crucial factor to induce effective and efficient resistance through genetic engineering in insects and fungi. To better understand the inheritance patterns and expression of transgenes, two genes (sporamin and chitinase PjChi-1) in T1 progeny of four single-copy T0 transformants were characterized. PCR detection revealed that the segregation ratio was 3 : 1 for tested plants of each T0 transformant, which agreed with the Mendelian rules. In RT-PCR analysis, 10 positive progeny plants of T0-11 line showed a stable expression of sporamin and PjChi-1 but not in wild type. Moreover, a higher expression level of sporamin gene in T1-11-3 was confirmed compared to the other progeny plants using Northern blot hybridization technique. Artificial inoculation of 10 plants (T1-11) with Lepidoptera larvae (Plutella xylostella) and fungus (Sclerotinia sclerotiorum) in in vitro bioassays showed significant resistance compared to the wild type. Progeny T1-11-3 showed the stronger resistance, which was consistent with the higher expression level of sporamin gene in Northern blot hybridization detection, whereas there was no difference in insect and fungi resistance among these positive T1-11 plants. These results indicate that both combined genes have been inherited from parental transformants to their progeny and showed a consistent resistance to insect and fungus in all positive T1 progeny.

Constrained preferences in nitrogen uptake across plant species and environments

Knowledge of determining factors for nitrogen uptake preferences and how they are modified in changing environments are critical to understand ecosystem nitrogen cycling and to predict plant responses to future environmental changes. Two ¹⁵N tracer experiments utilizing a unique differential labelled nitrogen source were employed in both African savannas and greenhouse settings. The results demonstrated that nitrogen uptake preferences were constrained by the climatic conditions. As mainly indicated by root δ¹⁵N signatures at 1:1 ammonium/nitrate ratio, in the drier environments, plants preferred nitrate and in the wetter environments they preferred ammonium. Nitrogen uptake preferences were different across different ecosystems (e.g. from drier to wetter environments) even for the same species. More significantly, our experiments showed that the plant progeny continued to exhibit the same nitrogen preference as the parent plants in the field, even when removed from their native environment and the nitrogen source was changed dramatically. The climatic constraint of nitrogen uptake preference is likely influenced by ammonium/nitrate ratios in the native habitats of the plants. The constancy in nitrogen preference has important implications in predicting the success of plant communities in their response to climate change, to seed bank use and to reforestation efforts.

Abiotic stress leads to somatic and heritable changes in homologous recombination frequency, point mutation frequency and microsatellite stability in Arabidopsis plants

In earlier studies, we showed that abiotic stresses, such as ionizing radiation, heavy metals, temperature and water, trigger an increase in homologous recombination frequency (HRF). We also demonstrated that many of these stresses led to inheritance of high-frequency homologous recombination, HRF. Although an increase in recombination frequency is an important indicator of genome rearrangements, it only represents a minor portion of possible stress-induced mutations. Here, we analyzed the influence of heat, cold, drought, flood and UVC abiotic stresses on two major types of mutations in the genome, point mutations and small deletions/insertions. We used two transgenic lines of Arabidopsis thaliana, one allowing an analysis of reversions in a stop codon-containing inactivated β-glucuronidase transgene and another one allowing an analysis of repeat stability in a microsatellite-interrupted β-glucuronidase transgene. The transgenic Arabidopsis line carrying the β-glucuronidase-based homologous recombination substrate was used as a positive control. We showed that the majority of stresses increased the frequency of point mutations, homologous recombination and microsatellite instability in somatic cells, with the frequency of homologous recombination being affected the most. The analysis of transgenerational changes showed an increase in HRF to be the most prominent effect observed in progeny. Significant changes in recombination frequency were observed upon exposure to all types of stress except drought, whereas changes in microsatellite instability were observed upon exposure to UVC, heat and cold. The frequency of point mutations in the progeny of stress-exposed plants was the least affected; an increase in mutation frequency was observed only in the progeny of plants exposed to UVC. We thus conclude that transgenerational changes in genome stability in response to stress primarily involve an increase in recombination frequency.

Transgenerational adaptation to heavy metal salts in Arabidopsis

Exposure to abiotic and biotic stress results in changes in plant physiology and triggers genomic instability. Recent reports suggest that the progeny of stressed plants also exhibit changes in genome stability, stress tolerance, and methylation. Here we analyzed whether exposure to Ni2+, Cd2+, and Cu2+ salts leads to transgenerational changes in homologous recombination frequency and stress tolerance. We found that the immediate progeny of stressed plants exhibited an increased rate of recombination. However, when the progeny of stressed plants was propagated without stress, recombination reverted to normal levels. Exposure of plants to heavy metals for five consecutive generations (S1–S5) resulted in recombination frequency being maintained at a high level. Skipping stress following two to three generations of propagation with 50 mM Ni2+ or Cd2+ did not decrease the recombination frequency, suggesting plant acclimation to upregulated recombination. Analysis of the progeny of plants exposed to Cu2+ and Ni2+ indicated higher stress tolerance to the heavy metal parental plants were exposed to. Tolerance was higher in plants propagated with stress for three to five generations, which resulted in longer roots than plants propagated on heavy metals for only one to two generations. Tolerance was also more prominent upon exposure to a higher concentration of salts. The progeny of stressed plants were also more tolerant to NaCl and methyl methane sulfonate.

Self-Fertilization of a Schlumbergera truncata Cultivar: Breakdown of Self-incompatibility

Plants of the genus Schlumbergera are popular houseplants cultivated throughout the world. While most species in the genus, including the cultivars of Schlumbergera truncata, have been found to be self-incompatible, one cultivar, S. truncata ‘Thor Olga’, is shown here to produce fruit containing viable seeds through self pollination. Three of seven flowers (~43%) set fruit, including two fruits from which viable seeds were collected. A total of 35 seeds from these two fruits were sown, of which nine germinated (~26% viability). The phylloclade shape for all nine progeny plants appeared similar to the S. × buckleyi type for the first year, with gently scalloped rounded edges and no teeth. After the first year, the phylloclade shape began to differentiate, with some remaining similar to the S. × buckleyi shape and others developing the typical S. truncata shape. One of the progeny resulting from the self fertilization was brought to flower, and, in addition to differing in flower color from the parent plant, the progeny plant is very dissimilar to its parent in its branching architecture and its arching pendulous habit, as well as in the size and shape of the phylloclades. The breakdown in self-incompatibility is thought to be associated with delayed pollination, since fresh mature pollen was placed on over-mature stigmas. This appears to be the first time successful self-fertilization of Schlumbergera truncata has been reported in the literature. It is reasonable to predict that other Schlumbergera cultivars/hybrids may likewise exhibit some degree of self-compatibility. The fact that the self-incompatibility mechanisms can be broken down, may lead to the development of a new range of cultivars with unique traits.

Evaluation of different methods for assessing the reproductive mode of weeping lovegrass plants, Eragrostis curvula (Schrad.) Nees

Weeping lovegrass is a forage grass cultivated in semiarid regions of the world that reproduces mainly by apomixis (diplospory), a process that involves the formation of asexual seeds and bypasses the processes of meiosis and fertilisation. The aim of this work was to evaluate and compare different techniques (cytoembryology, callose deposition, flow cytometry and progeny tests) to determine the reproductive mode of weeping lovegrass. Typical sexual and apomictic processes were clearly differentiated using cytoembryology, and different callose deposition patterns were observed in sexual and apomictic genotypes. Previous studies indicated that presence of callose on the cell wall of the megaspore mother cell is associated only with sexual processes. Nevertheless, our results also found callose deposition in apomictic genotypes, although clearly different from the pattern found in sexual processes, allowing discrimination between sexual and apomictic plants. Flow cytometry seed screening using individual seeds did not differentiate between sexual and apomictic plants as the embryo : endosperm DNA content ratio was similar in sexual and apomictic plants. Progeny tests using molecular markers showed uniform patterns in offspring from apomictic plants and variable patterns among the progeny of sexual plants. The results obtained from cytological studies and progeny tests were similar, indicating that both methods provide useful tools for determination of reproductive mode. However, the callose test with aniline blue was faster and easier to use than other techniques.

Autosegregation of enzyme loci Me1 and Gpi2 in agamospermous progenies of triploid sugarbeet plants

AbstractRatios of malic-enzyme (ME1) and glucosephosphate isomerase (GPI2) phenotypic classes were studied in agamospermous progenies of triploid sugar beet plants. It was shown that the ratio of enzymes phenotypic classes quite well accords with the calculations based on the supposition about reduplication of chromosome sites carrying alleles of enzyme loci accompanied by a loss of excessive allelic copies in the first cell division under embryogenesis. Polyteny – conditioned allelic dose increase leads to the occurrence of alleles – absent in the initial parent – at a certain frequency in the developing progeny. The notions of “meiotic autosegregation” and “mitotic autosegregation” – typical of meiotic and mitotic agamospermy, respectively, – were introduced; the term locus “polygenotype” characterizing the allelic composition of locus, number of chromosomes and a copies number of chromatides sites carrying marker-locus alleles in the cell before entering embryogenesis was also introduced.

Mating system parameters and genetic structure in Argentinean populations of Acacia caven (Leguminosae, Mimosoideae)

Acacia caven (Mol.) Mol. is native to South America. The species is a leguminous, woody small tree that is considered to have certain potential as a managed silvopastoral crop. Six varieties have been described for the species based on both morphological traits and molecular markers. Little information is available on its mating system. The main objectives of this work were to test the hypothesis that A. caven is an outcrosser and to estimate parameters of its mating system and population structure on the basis of isozyme markers. In the four populations studied, a high homozygote excess was found in the progeny population but not in the mother plant genotypes. The estimate for the multi-locus outcrossing rate (tm) was high (≥0.957) in all populations, indicating that Acacia caven is a predominantly outcrosser species. The results of genetic structure analysis within each population indicated that differences in allelic frequencies among families in all of the populations studied are highly significant. The difference in F estimates between progeny and mother plants suggests some selection favouring heterozygotes between the seedling and adult stages. Therefore, a strategy for ex situ conservation might emphasise sampling more populations with a relative large number of trees per site.

Transgenic tomato plants expressing recA and NLS-recA-licBM3 genes as a model for studying meiotic recombination

Homologous DNA recombination in eukaryotes is necessary to maintain genome stability and integrity and for correct chromosome segregation and formation of new haplotypes in meiosis. At the same time, genetic determination and nonrandomness of meiotic recombination restrict the introgression of genes and generation of unique genotypes. As one of the approaches to study and induce meiotic recombination in plants, it is recommended to use the recA gene of Escherichia coli. It is shown that the recA and NLS-recA-licBM3 genes have maternal inheritance and are expressed in the progeny of transgenic tomato plants. Plants expressing recA or NLS-recA-licBM3 and containing one T-DNA insertion do not differ in pollen fertility from original nontransgenic forms and can therefore be used for comparative studies of the effect of bacterial recombinases on meiotic recombination between linked genes.

Agrobacterium mediated transformation of indica rice (Oryza sativa L.) for insect resistance

The rice leaffolder (RLF), Cnaphalocrocis medinalis is an important pest of rice that causes severe damage in many areas of the world. The plants were transformed with fully modified (plant codon optimized) synthetic Cry1C coding sequences as well as with the hpt and gus genes, coding for hygromycin phosphotransferase and β-glucuronidase, respectively. Cry1C sequences placed under the control of doubled 35S promoter plus the AMV leader sequence, and hpt and gus genes driven by cauliflower mosaic virus 35S promoter, were used in this study. Embryogenic calli after cocultivation with Agrobacterium were selected on the medium containing hygromycin B. A total of 67 hygromycin-resistant plants were regenerated. PCR and Southern blot analyses of primary transformants revealed the stable integration of Cry1C coding sequences into the rice genome with predominant single copy integration. R1 progeny plants disclosed a monogenic pattern (3:1) of transgene segregation as confirmed by molecular analyses. These transgenic lines were highly resistant to rice leaffolder (RLF), Cnaphalocrocis medinalis as revealed by insect bioassay.

Virus‐mediated efficient induction of epigenetic modifications of endogenous genes with phenotypic changes in plants

Gene silencing through transcriptional repression can be induced by targeting double-stranded RNA (dsRNA) to a gene promoter. It has been reported that a transgene was silenced by targeting dsRNA to the promoter, and the silenced state was inherited to the progeny plant even after removal of the silencing inducer from cells. In contrast, no plant has been produced that harbors silenced endogenous gene after removal of promoter-targeting dsRNA. Here, we show that heritable gene silencing can be induced by targeting dsRNA to the endogenous gene promoters in petunia and tomato plants, using the Cucumber mosaic virus (CMV)-based vector. We found that efficient silencing of endogenous genes depends on the function of the 2b protein encoded in the vector virus, which has the ability to facilitate epigenetic modifications through the transport of short interfering RNA to nucleus. Bisulfite sequencing analyses on the targeted promoter in the virus-infected and its progeny plants revealed that cytosine methylation was found not only at CG or CNG but also at CNN sites. The observed inheritance of asymmetric DNA methylation is quite unique, suggesting that plants have a mechanism to maintain even asymmetric methylation. This CMV-based gene silencing system provides a useful tool to artificially modify DNA methylation in plant genomes and elucidate the mechanism for epigenetic controls.

Tissue Culture-Induced Novel Epialleles of aMybTranscription Factor Encoded bypericarp color1in Maize

Plants regenerated from tissue culture often display somaclonal variation, that is, somatic and often meiotically heritable phenotypic variation that can result from both genetic and epigenetic modifications. To better understand the molecular basis of somaclonal variation, we have characterized four unique tissue culture-derived epialleles of the pericarp color1 (p1) gene of maize (Zea mays L.). The progenitor p1 allele, P1-wr, is composed of multiple head-to-tail tandemly arranged copies of the complete gene unit and specifies brick-red phlobaphene pigmentation in the cob glumes. The novel epialleles identified in progeny plants regenerated from tissue culture showed partial to complete loss of p1 function indicated by pink or colorless cob glumes. Loss of pigmentation was correlated with nearly complete loss of p1 steady-state transcripts. DNA gel-blot analysis and genomic bisulfite sequencing showed that silencing of the epialleles was associated with hypermethylation of a region in the second intron of P1-wr. Presence of Unstable factor for orange1 (Ufo1), an unlinked epigenetic modifier of p1, restored the cob glume pigmentation in the silenced alleles, and such reactivation was accompanied by hypomethylation of the p1 sequence. This observation confirmed that silencing of the epialleles is indeed due to epigenetic modifications and that the p1 epialleles were capable of functioning in the presence of the correct trans-acting factors. While the low-copy regions of the genome generally undergo hypomethylation during tissue culture, our study shows that the tandemly repeated genes are also prone to hypermethylation and epigenetic silencing.

Tuber transmission of ‘Candidatus Liberibacter solanacearum’ and its association with zebra chip on potato in New Zealand

Zebra chip, an emerging disease of potatoes, has recently been associated with ‘Candidatus Liberibacter solanacearum’ in New Zealand. The phloem-limited bacterium is known to be vectored by the tomato potato psyllid (Bactericera cockerelli). In this study, the role of tuber transmission in the spread of Ca. L. solanacearum was investigated by re-planting potato tubers infected with Ca. L. solanacearum in the absence of the psyllid. Nested PCR demonstrated that Ca. L. solanacearum could be transmitted from the mother tubers both to the foliage of growing plants and to progeny tubers, resulting in symptomatic and asymptomatic plants. Of 62 Ca. L. solanacearum-infected tubers four did not sprout symptomatic of zebra chip. A further two plants developed foliar symptoms associated with zebra chip during the growing season and died prematurely. Fifty-six of the infected tubers produced asymptomatic plants, although Ca. L. solanacearum was detected in the foliage of 39 of them indicative of transmission into asymptomatic progeny plants. At harvest, Ca. L. solanacearum was found in the daughter tubers of only five of the 39 asymptomatic plants, and only one of these plants was found to have zebra chip symptoms in the daughter tubers. Our results show that tuber transmission of Ca. L. solanacearum could play a role in the life cycle of this pathogen, providing a source for acquisition by Bactericera cockerelli and for movement of the pathogen to other regions of New Zealand via transport of seed tubers.