Nicotiana Tabacum Cultivars Research Articles

Arabis mosaic virus in Grapevines in New York State.

In a limited survey of commercial vineyards and a germplasm repository in Ontario County, NY, 20 vines of Vitis sp. were tested in fall and spring 2010 to 2012 for viruses using a double-antibody sandwich (DAS)-ELISA and macroarray with oligonucleotide probes for grapevine viruses ((3) and unpublished). The plants selected for analysis included those showing atypical growth including leaf deformation, yellowing, cupping or spotting, vein clearing, shortening of internodes, and reduced vigor. Arabis mosaic virus (ArMV; genus Nepovirus, family Secoviridae) was detected in leaf tissue and wood scrapings in two vines using the DAS-ELISA with antibodies from Bioreba (Reinach, Switzerland). The ArMV positive vines were from Vitis hybrid cultivars Noah and Geisenheim 26. ArMV was also detected in these two vines using the macroarray, with hybridization observed to 24 of 32 oligonucleotide probes specific to this virus. To confirm the identification of the virus, total RNAs were extracted from leaf tissues, hybridized with random hexamers, and reverse-transcribed using MMLV reverse transcriptase (Life Technologies, Grand Island, NY). Complementary DNAs were amplified by PCR using an IQ supermix (BioRad, Hercules, CA), and two sets of generic primers for nepoviruses (1,4). Thermocycler conditions were 94°C 5 min (1×); 94°C 30 s, 50°C 30 s, and 69°C 2 min (35×), and 72°C for 5 min. The PCR products were sequenced directly. Sequences from the 340-bp products obtained from cultivars Geisenheim 26 (GenBank Accession No. HE984333) and Noah (HE984334) using the Wei et al. primers (4) had 76 to 84% sequence identity to ArMV RNA1 GenBank accessions GQ369528 and AY303786. Sequences from the 301-bp products obtained from cultivars Geisenheim 26 (HE984335) and Noah (HE984336) using the Digiaro et al. primers (1) had 87 to 91% sequence identity to ArMV RNA2 GenBank accessions AY017339 and X81814. ArMV was mechanically transmitted from Geisenheim 26 to Nicotiana tabacum cultivar Xanthi NN. Inoculation gave rise to necrotic local lesions on the inoculated leaves of five plants in each of two experiments (10 of 10 plants total). The presence of ArMV in tobacco was confirmed by DAS-ELISA. Thus, the presence of ArMV in New York grapevines has been confirmed by the detection of the coat protein antigen, virus specific oligonucleotide probes, and the sequencing of portions of both genomic RNAs. There are limited reports of ArMV in North America and in grapevine in particular (2), but with a wide host range and seed and nematode transmissibility, ArMV has the ability to become more widespread among grapevine and other crops.

Non-Functionalization of Two CYP82E Nicotine N-Demethylase Genes Abolishes Nornicotine Formation in Nicotiana langsdorffii

Nornicotine is formed from nicotine by nicotine N-demethylase, a CYP82E family monooxygenase, and accumulates to high levels in some tobacco (Nicotiana tabacum) cultivars and many wild Nicotiana species. Nicotiana langsdorffii does not form nornicotine, whereas the closely related species N. alata accumulates this alkaloid abundantly. We show here that the two nicotine N-demethylase genes in N. langsdorffii have been inactivated by different molecular mechanisms. We identified four N. alata CYP82E genes that encode functional nicotine N-demethylases. In N. langsdorffii, however, one CYP82E gene encoding a functional enzyme was not expressed at all, whereas the other was weakly expressed but contained a one-nucleotide deletion in the first exon, yielding a truncated protein. Expression analysis of interspecific F(1) hybrids between N. alata and N. langsdorffii indicated that cis-acting polymorphisms abolish expression of the otherwise functional CYP82E gene in N. langsdorffii. Segregation analysis of tobacco alkaloids and individual CYP82E alleles in F(2) progeny revealed that duplicated CYP82E genes in both species are genetically linked, and provide genetic evidence that CYP82E genes are solely responsible for nornicotine formation in these wild Nicotiana species.

Utility of the P19 suppressor of gene‐silencing protein for production of therapeutic antibodies in Nicotiana expression hosts

To study how the P19 suppressor of gene-silencing protein can be used effectively for the production of therapeutic glycoproteins, the following factors were examined: the genetic elements used for expressing recombinant proteins; the effect of different P19 concentrations; compatibility of P19 with various Nicotiana tabacum cultivars for transgenic expression; the glycan profile of a recombinant therapeutic glycoprotein co-expressed with P19 in an RNAi-based glycomodified Nicotiana benthamiana expression host. The coding sequences for the heavy and light chains of trastuzumab were cloned into five plant expression vectors (102-106) containing different 5' and 3' UTRs, designated as vector sets 102-106 mAb. The P19 protein of Tomato bushy stunt virus (TBSV) was also cloned into vector 103, which contained the Cauliflower mosaic virus (CaMV) 35S promoter and 5'UTR together with the terminator region of the nopaline synthase gene of Agrobacterium. Transient expression of the antibody vectors resulted in different levels of trastuzumab accumulation, the highest being 105 and 106 mAb at about 1% of TSP. P19 increased the concentration of trastuzumab approximately 15-fold (to about 2.3% of TSP) when co-expressed with 103 mAb but did not affect antibody levels with vectors 102 and 106 mAb. When 103 mAb was expressed together with P19 in different N. tabacum cultivars, all except Little Crittenden showed a marked discolouring of the infiltrated areas of the leaf and decreased antibody expression. Co-expression of P19 also abolished antibody accumulation in crosses between N. tabacum cv. I-64 and Little Crittenden, indicating a dominant mode of inheritance for the observed P19-induced responses.

Variation of genomic DNA methylation in the nitrate reductase gene of sibling tobacco (Nicotiana tabacum) cultivars

To better understand genomic DNA methylation in sibling plant cultivars, methylation-sensitive amplification polymorphism analysis was used to investigate two sibling tobacco cultivars, Yunyan85 and Yunyan87, and their two parents, K326 and Yunyan No. 2. Differences in the degree of genomic DNA methylation were found among the four tobacco cultivars. Compared with parents, the two sibling cultivars had fewer methylated sites. Twenty-nine methylation-sensitive amplification polymorphism fragments that exhibited methylation alteration in the four tobacco cultivars were recovered and sequenced. BLAST (nucleotide BLAST) searches showed that two of the 29 sequences have 99% similarity with nucleotides 1442-1694 of the nia-1 gene and the other 27 sequences contain GC, CAAT or TATA box. The nitrate reductase genes from Yunyan87, K326 and Yunyan No. 2 were found to be identical; however, the third intron of the nitrate reductase gene from Yunyan85 was different compared to the third introns of Yunyan87, K326 and Yunyan No. 2. We conclude that methylation alteration of promoter regions could be responsible for the different phenotypes in tobacco and that introns of the nitrate reductase gene can vary as a result of intra-species crossing in tobacco.

Biological and molecular characterization of Soybean yellow common mosaic virus, a new species in the genus Sobemovirus

A novel soybean-infecting sobemovirus termed Soybean yellow common mosaic virus (SYCMV) was characterized. The virus has a single, positive-strand RNA genome of 4152 nucleotides. The virus contains four putative open reading frames encoding P1 (78–566 nt), polyprotein ORF2a (524–2248 nt), polymerase domain ORF2b (1852–3417 nt), and CP (3227–4030 nt). The entire nucleotide sequence of SYCMV showed 31.2–71.3% nucleotide identity with the previously known eleven species of sobemovirus. In host range analysis of SYCMV, in which twenty one species and three different Nicotiana tabacum cultivars belonging to seven families were inoculated with the virus, SYCMV had a narrow host range, infecting only Glycine max and G. soja. Based on the obtained sequence, full-length clones of SYCMV were constructed. Symptoms produced by inoculation with clones were indistinguishable from those produced by inoculation with sap from symptomatic plants. Viral RNA accumulation of SYCMV was detected in the upper leaves by Northern blotting. This indicated that full-length clones of SYCMV were sufficient to produce disease symptoms. Genomic organization, the predicted amino acid sequence, and phylogenetic analyses with known sobemoviruses confirmed the assignment of SYCMV as a new member of the genus Sobemovirus.

Analysis of DNA methylation variation in sibling tobacco ( Nicotiana tabacum ) cultivars

Amplified fragment length polymorphism (AFLP) and methylation-sensitive amplification polymorphism (MSAP) analysis were used to investigate the genome of two sibling tobacco cultivars, Yunyan85 and Yunyan87, their parent K326 and the other tobacco cultivar NC89. AFLP analysis indicated that, the genome primary structure variations were not obviously detected among Yunyan85 and Yunyan87 and K326. However, the methylation extent had different alteration between the sibling tobacco cultivars relative to their parent; it rose to 42.97 and 36.55% in Yunyan85 and Yunyan87, respectively. Both the full and semi-methylation modifications on the ‘CCGG/GGCC’ site were significantly increased in Yunyan85 and Yunyan87, however, the full-methylation modification on the ‘CCGG/GGCC’ site in Yunyan85 was significantly higher than the one in Yunyan87. Among the polymorphic methylated sites, most of them (53.70%) were hypermethylation sites, 35 (16.20%) sites were demethylation modification and 62 (28.70%) sites were uncertain methylation modification. The sequences involved in methylation alteration mainly included promoter regions. The results in this study have provided a better understanding of gene expression phenotype. Key words : Nicotiana tabacum, methylation, amplified fragment length polymorphism (AFLP), methylationsensitive amplification polymorphism (MSAP).

Production and characterization of anti‐(mucin MUC1) single‐domain antibody in tobacco (Nicotiana tabacum cultivar Xanthi)

Members of the Camelidae (camels, dromedaries, llamas, alpacas, guanacos and vicunas) are known to produce Igs (immunoglobulins) devoid of light chains and CH1s (constant heavy-chain domains). The antigen-specific binding fragments of these heavy-chain antibodies therefore comprise one single domain (the so-called 'VHH') and are of great importance in biotechnological applications. To evaluate the expression and biological activity of sdAbs (single-domain antibodies) in plants, which, on account of their small size and antigen-recognition properties, would have a major impact on antibody-engineering strategies, we constructed a pBI121-VHH gene encoding the recombinant sdAb fragments with specificity for a cancer-associated mucin, MUC1. Analysis of transgenic tobacco (Nicotiana tabacum cultivar Xanthi) plants by PCR and Western blotting demonstrated the expression of sdAb, while ELISA results with various MUC1 antigens and immunocytochemistry with cancerous cell lines confirmed that the activity of these molecules compared favourably with that of the parent recombinant antibodies. Protein purification was achieved by using sequential (NH4)2SO4 precipitation, gel filtration and immunoaffinity chromatography. Analysis of the purified VHH by ELISA indicated that the purified antibody fragments were able to react successfully with a MUC1-related peptide. These results reaffirm that the tobacco plant is a suitable host for the production of correctly folded VHH antibody fragments with diagnostic and therapeutic applications.

The presence of jasmonate-inducible lectin genes in some but not all Nicotiana species explains a marked intragenus difference in plant responses to hormone treatment

Tobacco (Nicotiana tabacum L. cv Samsun NN) leaves accumulate a cytoplasmic/nuclear lectin, called Nictaba, in response to methyl jasmonate. To check whether, and if so to what extent, the specific induction of this lectin applies to related species, a collection of 19 Nicotiana species--covering 12 Nicotiana sections and eight Nicotiana tabacum cultivars--was screened for their capability to synthesize the jasmonate-inducible lectin. Protein analyses by agglutination assays and western blot confirmed that only nine out of the 19 species examined synthesize lectin after jasmonate treatment. Remarkably, all allotetraploid cultivars of the N. tabacum L. species tested express the lectin after jasmonate treatment. PCR analyses demonstrated that all responsive species possess one or more lectin genes, whereas no lectin gene(s) could be traced in the non-responding species. The number of introns present in the lectin genes varies between zero and two. Four tobacco species/cultivars contain both intronless Nictaba genes as well as lectin genes with introns. These findings provide the first firm evidence for a striking intragenus difference with respect to the activation of a well-defined jasmonate-inducible gene that can be correlated with the presence/absence of orthologous genes in the genomes of closely related species from a single plant genus. In addition, the differential response of closely related tobacco species illustrates that in the field of plant hormone research, care must be taken when extrapolating results obtained with a particular model system to other--even taxonomically closely related--species.

Internalisation of cell-penetrating peptides into tobacco protoplasts

Cells are protected from the surrounding environment by plasma membrane which is impenetrable for most hydrophilic molecules. In the last 10 years cell-penetrating peptides (CPPs) have been discovered and developed. CPPs enter mammalian cells and carry cargo molecules over the plasma membrane with a molecular weight several times their own. Known transformation methods for plant cells have relatively low efficiency and require improvement. The possibility to use CPPs as potential delivery vectors for internalisation in plant cells has been studied in the present work. We analyse and compare the uptake of the fluorescein-labeled CPPs, transportan, TP10, penetratin and pVEC in Bowes human melanoma cells and Nicotiana tabacum cultivar (cv.) SR-1 protoplasts (plant cells without cell wall). We study the internalisation efficiency of CPPs with fluorescence microscopy, spectrofluorometry and fluorescence-activated cell sorter (FACS). All methods indicate, for the first time, that these CPPs can internalise into N. tabacum cv. SR-1 protoplasts. Transportan has the highest uptake efficacy among the studied peptides, both in mammalian cells and plant protoplast. The internalisation of CPPs by plant protoplasts may open up a new effective method for transfection in plants.

Ozone-response mechanisms in tobacco: implications of polyamine metabolism.

• Polyamines have been suggested to counteract oxidative damage in plants. Here, we present a detailed analysis of polyamine accumulation and its relationship to photosynthetic parameters in two tobacco (Nicotiana tabacum) cultivars (ozone-sensitive Bel W3 and ozone-tolerant Bel B) after a single ozone pulse and after a 1-month exposure in the open air. • Free putrescine accumulated in undamaged tissue of both cultivars, whereas putrescine conjugated to soluble and cell-wall bound components accumulated predominantly in tissue undergoing cell death in Bel W3 plants. Accumulation was caused by a redirection of the conjugation pathway, as well as by a transient increase in arginine decarboxylase and ornithine decarboxylase specific activity. This increase seemed to be regulated at post-transcriptional level. • Measurements of chlorophyll content and fluorescence showed that, in addition to visible necrotic lesions, Bel W3 plants suffered considerable photosynthetic damage in other parts of the leaf. • Accumulation of conjugated putrescine is part of the ozone-induced programmed cell death response in Bel W3 plants. Ozone-induced synthesis of free putrescine is not correlated with ozone-resistance in Bel B plants, which are apparently impaired in signal transduction pathways that are necessary to control the cellular redox state. However, Bel B plants are able to perceive ozone stress and to induce a series of defense mechanisms without activating hypersensitive cell death.

Biomonitoring of tropospheric ozone phytotoxicity in rural Catalonia

The ozone (O 3) phytotoxicity in rural areas of Catalonia (NE Spain) and the biomonitoring capacity of Bel-W3 tobacco ( Nicotiana tabacum) cultivars were assessed by determining the percentage of leaf area injured by ozone in plants of this cultivar exposed from spring to autumn since 1995–1999. The study was conducted simultaneously on nine field sites where ground level ozone concentrations and meteorological parameters were continuously monitored. Geographical, seasonal and annual variations of ozone damage rate and their links with meteorological conditions were studied. Ozone concentrations and leaf damage increased at the end of spring and the beginning of summer. Coastal sites generally presented higher O 3 concentrations than inland and mountain sites. These mountain sites were the most sensitive ones to ozone toxicity. The ozone concentrations correlated well with ozone injury. However, at this local scale the ozone levels did not fully account for all the observed injury (only 11%). The response of tobacco plants to ozone concentrations and therefore its biomonitoring capacity depended also on different environmental conditions, mainly those linked to stomatal behaviour such as vapour pressure deficit. The categorization of leaf damage in 10% intervals and its averaging throughout the whole study period and the whole region, strongly improved (99% of variance accounted) the relationship with ozone concentrations expressed as AOT20 (accumulated over a cut-off of 20 ppb v). N. tabacum cultivar Bel-W3 is thus a very good biomonitor of ozone concentrations in the long term at the regional scale. Taking into account the phytotoxical response of this sensitive tobacco cultivar, we propose the 1.28 ppm v h biweekly AOT40 (with a solar radiation threshold of 50 W m −2) as a damage threshold level for sensitive species.

Origin of the Black Shank Resistance Gene, Ph, in Tobacco Cultivar Coker 371-Gold.

Flue-cured tobacco (Nicotiana tabacum) cultivar Coker 371-Gold (C 371-G) possesses a dominant gene, Ph, that confers high resistance to black shank disease, caused by race 0 of the soil-borne pathogen Phytophthora parasitica var. nicotianae. The origin of this gene is unknown. Breeding lines homozygous for the Ph gene were hybridized with NC 1071 and L8, flue-cured and burley genotypes known to possess qualitative resistance genes from Nicotiana plumbaginifolia and N. longiflora, respectively. The F1 hybrids were out-crossed to susceptible testers and the progenies evaluated in field black shank nurseries and in greenhouse disease tests with P. parasitica var. nicotianae race 0. Results showed that Ph was allelic to Php from N. plumbaginifolia in NC 1071. Testcross populations of hybrids between burley lines homozygous for Ph and L8, possessing Phl from N. longiflora, showed that Ph and Phl integrated into the same tobacco chromosome during interspecific transfer. Nevertheless, the two loci were estimated to be 3 cM apart. Random amplified polymorphic DNA (RAPD) analyses of the testcross progenies confirmed that recombination between the two loci was occurring. Forty-eight RAPD markers linked to Ph in doubled haploid lines were used in cluster analyses with multiple accessions of N. longiflora and N. plumbaginifolia, breeding lines L8, NC 1071, and DH92-2770-40, and cultivars K 326, Hicks, and C 371-G. A cladogram or region tree confirmed the data obtained from field and greenhouse trials, that Ph, transferred from C 371-G to DH92-2770-40, and Php in NC 1071 were allelic and originated from N. plumbaginifolia.

Indoor and outdoor genotoxic load detected by the Comet assay in leaves of Nicotiana tabacum cultivars Bel B and Bel W3.

Environmental pollution assessment and control are priority issues for both developed and developing countries of the world. The use of plant material for a more complete picture of environmental health appears to be particularly appealing. Here we validate a previous plant-adapted Comet assay on leaf tissues of Nicotiana tabacum cultivars Bel B and Bel W3. The effects of H(2)O(2) on DNA damage in Bel B and Bel W3 agree with the hypothesis that some component of the machinery that protects DNA integrity from oxidative stress may be impaired in cv. Bel W3. Exposure in the field on sunny summer days (peak ozone concentration >80 p.p.b.) showed significantly higher DNA damage in cv. Bel W3 if plants were collected and subjected to the Comet assay when the air ozone concentration was reaching its peak value, but not when plants were sampled early in the morning and hence after a period of low ozone concentration. The different results suggest that Bel W3 possesses a less efficient recovery apparatus that requires a longer period of activity to be effective and/or is less protected against reactive oxygen species production during exposure to ozone. However, it cannot be excluded that the increase in mean DNA damage is the result of the presence of a genotoxic agent(s) other than ozone. Interestingly, Bel W3 also appears to be more responsive, compared with Bel B, when exposed to ambient indoor pollutants. The use of cv. Bel W3 increases the sensitivity of the assay under both indoor and field conditions. However, different classes of mutagens should be tested to define the range of profitable utilization of this tobacco cultivar for environmental genotoxicity detection.

Strain-Specific Interaction of the Tobacco Etch Virus NIa Protein with the Translation Initiation Factor eIF4E in the Yeast Two-Hybrid System

The NIa protein of potyviruses provides VPg and proteolytic functions during virus replication. It has also been shown to confer host genotype-specific movement functions in plants. Specifically, NIa from tobacco etch virus (TEV)-Oxnard, but not from most other strains, confers the ability to move long distances in Nicotiana tabacum cultivar “V-20.” This led to the hypothesis that all or part of NIa may interact with one or more cellular factors. To identify cellular proteins that interact with NIa in a host- or strain-specific manner, a yeast two-hybrid search of a tomato cDNA library was done. Ten proteins that interacted with NIa were recovered, with translation initiation factor eIF4E being by far the most common protein identified. Interaction of eIF4E with NIa was shown to be TEV strain-specific. eIF4E from both tomato and tobacco interacted well with NIa from the HAT strain, but not from the Oxnard strain. However, using chimeric NIa proteins, the determinant for systemic infection of V20 plants was found to be genetically distinct from the determinant controlling eIF4E interaction. In TEV–eIF4E coexpression experiments, evidence suggesting that eIF4E provides a positive effect on genome amplification was obtained.

The expression of a baculovirus‐derived chitinase gene increased resistance of tobacco cultivars to brown spot (Alternaria alternata)

SummaryThe Autographa californica multiple nucleopolyhedrovirus (AcMNPV) chitinase gene coding region was amplified using the polymerase chain reaction, inserted into a plasmid (pROK‐2) and replicated in Escherichia coli XL1–blue. The recombinant plasmid was mobilised into Agrobacterium tumefaciens LBA 4404 and inoculated into tobacco leaf discs. The presence of the expressed chitinase in foliar tissue of kanamycin‐resistant plantlets of three Nicotiana tabacum cultivars (CF80, K326 and Xanthi‐nc) was inferred using immunoblotting, and enzyme activity was confirmed using a fluorometric assay. Confocal laser scanning microscopy with immunofluorescent staining of foliar sections from N. tabacum Xanthi‐nc expressing the viral chitinase indicated that the enzyme was restricted to the vascular tissue. Heliothis virescens larvae fed on leaf tissue expressing chitinase were not impaired either in their development to pupation or in their feeding behaviour, in comparision with their counterparts that had consumed similar amounts of untransformed tobacco leaf tissue. By contrast, when tobacco leaves were mechanically inoculated with Alternaria alternata, very few brown spots were observed at inoculation sites in chitinase‐expressing tissue, whereas large and spreading lesions formed in untransformed tobacco tissue. Of all lines that were transformed, as determined by kanamycin resistance, 59% had fewer symptoms of disease (smaller disease indices) than those for untransformed controls.

Endogenous Methyl Salicylate in Pathogen-Inoculated Tobacco Plants1

Abstract The tobacco (Nicotiana tabacum) cultivar Xanthi-nc (genotype NN) produces high levels of salicylic acid (SA) after inoculation with the tobacco mosaic virus (TMV). Gaseous methyl salicylate (MeSA), a major volatile produced in TMV-inoculated tobacco plants, was recently shown to be an airborne defense signal. Using an assay developed to measure the MeSA present in tissue, we have shown that in TMV-inoculated tobacco plants the level of MeSA increases dramatically, paralleling increases in SA. MeSA accumulation was also observed in upper, noninoculated leaves. In TMV-inoculated tobacco shifted from 32 to 24°C, the MeSA concentration increased from nondetectable levels to 2318 ng/g fresh weight 12 h after the temperature shift, but subsequently decreased with the onset of the hypersensitive response. Similar results were observed in plants inoculated withPseudomonas syringae pathovarphaseolicola, in which MeSA levels were highest just before the hypersensitive response-induced tissue desiccation. Transgenic NahG plants unable to accumulate SA also did not accumulate MeSA after TMV inoculation, and did not show increased resistance to TMV following MeSA treatment. Based on the spatial and temporal kinetics of its accumulation, we conclude that tissue MeSA may play a role similar to that of volatile MeSA in the pathogen-induced defense response.

Long-term resistance to tomato spotted wilt virus in transgenic tobacco cultivars expressing the viral nucleoprotein gene: greenhouse and field tests

We examined the resistance phenotype of a large number of transgenic tobacco plants originating from 12 commercial (Nicotiana tabacum) cultivars expressing the sense form of the nucleoprotein (N) gene of L3, a Bulgarian isolate of tomato spotted wilt virus (TSWV). The analysis revealed that transgenic plants are completely protected against the homologous L3 isolate of TSWV irrespective of whether or not they contain detectable levels of translational product. The effectiveness of protection against the virus was investigated upon mechanical inoculation under greenhouse conditions and in field trials. Non-segregating resistant lines were selected and the inheritance of the resistance to TSWV was analysed in successive generations (R3–R6). Extensive tests under controlled conditions and two-year field trials proved that the resistance to TSWV is stable in different environments and is a stably inherited trait.

Increased Salt and Drought Tolerance by D-Ononitol Production in Transgenic Nicotiana tabacum L.

A cDNA encoding myo-inositol O-methyltransferase (IMT1) has been transferred into Nicotiana tabacum cultivar SR1. During drought and salt stress, transformants (I5A) accumulated the methylated inositol D-ononitol in amounts exceeding 35 [mu]mol g-1 fresh weight In I5A, photosynthetic CO2 fixation was inhibited less during salt stress and drought, and the plants recovered faster than wild type. One day after rewatering drought-stressed plants, I5A photosynthesis had recovered 75% versus 57% recovery with cultivar SR1 plants. After 2.5 weeks of 250 mM NaCl in hydroponic solution, I5A fixed 4.9 [plus or minus] 1.4 [mu]mol CO2 m-2 s-1, whereas SR1 fixed 2.5 [plus or minus] 0.6 [mu]mol CO2 m-2 s-1. myo-Inositol, the substrate for IMT1, increases in tobacco under stress. Preconditioning of I5A plants in 50 mM NaCl increased D-ononitol amounts and resulted in increased protection when the plants were stressed subsequently with 150 mM NaCl. Pro, Suc, Fru, and Glc showed substantial diurnal fluctuations in amounts, but D-ononitol did not. Plant transformation resulting in stress-inducible, stable solute accumulation appears to provide better protection under drought and salt-stress conditions than strategies using osmotic adjustment by metabolites that are constitutively present.

AC Gayed flue-cured tobacco

AC Gayed is a flue-cured tobacco (Nicotiana tabacum) cultivar bred at the Pest Management Research Centre of Agriculture and Agri-Food Canada. It is a a black root rot (Chalara elegans) resistant, backcross derivative of Delgold (ST205/PB19//*5 Delgold) (Pandeya and White 1984). The resistance gene originated from Nicotiana debneyi. AC Gayed is adapted to the tobacco production areas of Ontario. It has similar grade index, but slightly lower yield than Delgold when grown in disease-free conditions. Key words: Nicotiana tabacum, black root rot resistance, backcross

AC Maridel flue-cured tobacco

AC Maridel is a flue-cured tobacco (Nicotiana tabacum) cultivar bred collaboratively by the Pest Management Research Centre and the Charlottetown Research Centre of Agriculture and Agri-Food Canada. It is a cultivar with high yield, improved leaf quality and is resistant to black root rot (Chalara elegans). It resulted from crosses between two breeding lines originally selected at Delhi (80M11/80K2G). AC Maridel is adapted to the tobacco growing areas of Prince Edward Island. Key words: Nicotiana tabacum, black root rot resistance