The Histological, Effectoromic, and Transcriptomic Analyses of Solanum pinnatisectum Reveal an Upregulation of Multiple NBS-LRR Genes Suppressing Phytophthora infestans Infection.

Utilization of disease resistance components from wild potatoes is a promising and sustainable approach to control Phytophthora blight. Here, we combined avirulence (Avr) genes screen with RNA-seq analysis to discover the potential mechanism of resistance in Mexican wild potato species, Solanum pinnatisectum. Histological characterization displayed that hyphal expansion was significantly restricted in epidermal cells and mesophyll cell death was predominant, indicating that a typical defense response was initiated in S. pinnatisectum. Inoculation of S. pinnatisectum with diverse Phytophthora infestans isolates showed distinct resistance patterns, suggesting that S. pinnatisectum has complex genetic resistance to most of the prevalent races of P. infestans in northwestern China. Further analysis by Avr gene screens and comparative transcriptomic profiling revealed the presence and upregulation of multiple plant NBS-LRR genes corresponding to biotic stresses. Six NBS-LRR alleles of R1, R2, R3a, R3b, R4, and Rpi-smira2 were detected, and over 60% of the 112 detected NLR proteins were significantly induced in S. pinnatisectum. On the contrary, despite the expression of the Rpi-blb1, Rpi-vnt1, and Rpi-smira1 alleles, fewer NLR proteins were expressed in susceptible Solanum cardophyllum. Thus, the enriched NLR genes in S. pinnatisectum make it an ideal genetic resource for the discovery and deployment of resistance genes for potato breeding.

Interactive Effects of Wide-Spectrum Monochromatic Lights on Phytochemical Production, Antioxidant and Biological Activities of Solanum xanthocarpum Callus Cultures.

Solanum xanthocarpum is considered an important traditional medicinal herb because of its unique antioxidant, and anti-diabetic, anti-aging, and anti-inflammatory potential. Because of the over exploitation linked to its medicinal properties as well as destruction of its natural habitat, S. xanthocarpum is now becoming endangered and its supply is limited. Plant in vitro culture and elicitation are attractive alternative strategies to produce biomass and stimulate biosynthesis of medicinally important phytochemicals. Here, we investigated the potential influence of seven different monochromatic light treatments on biomass and secondary metabolites accumulation in callus culture of S. xanthocarpum as well as associated biological activities of the corresponding extracts. Among different light treatments, highest biomass accumulation was observed in white light-treated callus culture. Optimum accumulation of total flavonoid contents (TFC) and total phenolic contents (TPC) were observed in callus culture kept under continuous white and blue light respectively than control. Quantification of phytochemicals through HPLC revealed that optimum production of caffeic acid (0.57 ± 0.06 mg/g DW), methyl-caffeate (17.19 mg/g ± 1.79 DW), scopoletin (2.28 ± 0.13 mg/g DW), and esculetin (0.68 ± 0.07 mg/g DW) was observed under blue light callus cultures. Compared to the classic photoperiod condition, caffeic acid, methyl-caffeate, scopoletin, and esculetin were accumulated 1.7, 2.5, 1.1, and 1.09-folds higher, respectively. Moreover, high in vitro cell free antioxidant, anti-diabetic, anti-aging, and anti-inflammatory activities were closely associated with the production of these secondary metabolites. These results clearly showed the interest to apply multispectral light as elicitor of in vitro callus cultures S. xanthocarpum to promote the production of important phytochemicals, and allow us to propose this system as an alternative for the collection of this endangered species from the wild.

Spectral quality as an elicitor of bioactive compound production in Solanum aculeatissimum JACQ cell suspension.

Solanum aculeatissimum Jacq. is a common plant in much of Brazil. Despite containing metabolites with a wide range of pharmacological applications, there are few tissue culture reports for this plant. The possibility of large-scale in vitro production of this material has significant biotechnological potential. Therefore, the objective of this study was to investigate the effect of light conditions on the growth of cells in suspension, observing the production and yield of biomass and bioactive compounds and the enzymatic behavior. Calli obtained from leaf segments were cultured in solid medium supplemented with 1 mg L-1 of 2,4-D, 2.5 mg L-1 kinetin, pH 5.7, in the dark. After 110 days of subculture, the calli were transferred to liquid medium. Cells were kept in the dark under agitation at 110 rpm and 25 °C and subcultured every 30 days. After 90 days of culture, 20 mL aliquots of cell suspension were added to flasks containing approximately 20 mL of medium (1:1) and cultured at different wavelengths (white, green, blue, red, and blue/red) under a photoperiod of 16 h with irradiance of 50 µmol m-2 s-1) and in the absence of light. The experiment was performed in a 6 × 6 factorial design (light condition × culture time). The cell cultures showed viability throughout the entire cycle, and chlorogenic and ferulic acids, orientin, quercitrin and, in higher amounts, quercetin, were detected in the first 7 days of culture. There was an increase in superoxide dismutase and catalase and a decrease in ascorbate peroxidase after exposure to different light conditions; for phenylalanine ammonia lyase, no differences were observed. The different light conditions were not sufficient to trigger responses in the concentrations of bioactive compounds, despite the detection of increased levels of the enzymes involved in cellular homeostasis.

The ScRALF3 secreted peptide is involved in sporophyte to gametophyte signalling and affects pollen mitosis I.

Signalling events through small peptides are essential in multiple aspects of plant reproduction. The ScRALF3 Solanum chacoense Rapid Alkalinization Factor (RALF) peptide was previously shown to regulate multiple aspects of cell-cell communication between the surrounding sporophytic tissue and the female gametophyte during ovule development. We analysed the global expression pattern of ScRALF3 with GUS reporter gene under control of the ScRALF3 promoter and validated it with in situ hybridisation. To better understand the role of ScRALF3 we used three different RNA interference (RNAi) lines that reduced the expression of ScRALF3 during pollen development. Both expression methods showed the presence of ScRALF3 in different tissues, including stigma, style, vascular tissues and during stamen development. Down-regulation of ScRALF3 expression through RNAi showed drastic defects in early stages of pollen development, mainly on the first mitosis. These results suggest that the ScRALF3 secreted peptide regulates the transition from sporogenesis to gametogenesis in both male and female gametophytes.

Impedance Flow Cytometry: A Novel Technique in Pollen Analysis.

INTRODUCTION: An efficient and reliable method to estimate plant cell viability, especially of pollen, is important for plant breeding research and plant production processes. Pollen quality is determined by classical methods, like staining techniques or in vitro pollen germination, each having disadvantages with respect to reliability, analysis speed, and species dependency. Analysing single cells based on their dielectric properties by impedance flow cytometry (IFC) has developed into a common method for cellular characterisation in microbiology and medicine during the last decade. The aim of this study is to demonstrate the potential of IFC in plant cell analysis with the focus on pollen. METHOD: Developing and mature pollen grains were analysed during their passage through a microfluidic chip to which radio frequencies of 0.5 to 12 MHz were applied. The acquired data provided information about the developmental stage, viability, and germination capacity. The biological relevance of the acquired IFC data was confirmed by classical staining methods, inactivation controls, as well as pollen germination assays. RESULTS: Different stages of developing pollen, dead, viable and germinating pollen populations could be detected and quantified by IFC. Pollen viability analysis by classical FDA staining showed a high correlation with IFC data. In parallel, pollen with active germination potential could be discriminated from the dead and the viable but non-germinating population. CONCLUSION: The presented data demonstrate that IFC is an efficient, label-free, reliable and non-destructive technique to analyse pollen quality in a species-independent manner.

The FRK1 mitogen-activated protein kinase kinase kinase (MAPKKK) from Solanum chacoense is involved in embryo sac and pollen development.

The fertilization-related kinase 1 (ScFRK1), a nuclear-localized mitogen-activated protein kinase kinase kinase (MAPKKK) from the wild potato species Solanum chacoense, belongs to a small group of pMEKKs that do not possess an extended N- or C-terminal regulatory domain. Initially selected based on its highly specific expression profile following fertilization, in situ expression analyses revealed that the ScFRK1 gene is also expressed early on during female gametophyte development in the integument and megaspore mother cell and, later, in the synergid and egg cells of the embryo sac. ScFRK1 mRNAs are also detected in pollen mother cells. Transgenic plants with lower or barely detectable levels of ScFRK1 mRNAs lead to the production of small fruits with severely reduced seed set, resulting from a concomitant decline in the number of normal embryo sacs produced. Megagametogenesis and microgametogenesis were affected, as megaspores did not progress beyond the functional megaspore (FG1) stage and the microspore collapsed around the first pollen mitosis. As for other mutants that affect embryo sac development, pollen tube guidance was severely affected in the ScFRK1 transgenic lines. Gametophyte to sporophyte communication was also affected, as observed from a marked change in the transcriptomic profiles of the sporophytic tissues of the ovule. The ScFRK1 MAPKKK is thus involved in a signalling cascade that regulates both male and female gamete development.

Histochemical visualization of ROS and antioxidant response to viral infections of vegetable crops grown in Azerbaijan.

Extremes of environmental conditions, such as biotic stresses, strongly affect plant growth and development and may adversely affect photosynthetic process. Virus infection is especially problematic in crops, because unlike other diseases, its impact cannot be reduced by phytosanitary treatments. The vegetable crops (Solanum lycopеrsicum L, Cucurbita melo L., Cucumis sativus L., Piper longum L., Solánum melongéna L., Vicia faba L.) showing virus-like symptoms were collected from fields located in the main crop production provinces of Azerbaijan. Infection of the plants were confirmed by Enzyme-linked immunosorbent assay using commercial kits for the following viruses: Tomato yellow leaf curl virus, Tomato mosaic virus, Tomato chlorosis virus, Melon necrotic spot virus and Cucumber mosaic virus, Bean common mosaic virus and Bean yellow mosaic virus. Generation sites of superoxide and hydrogen peroxide radicals and activities of enzymes involved in the detoxification of reactive oxygen species (catalase, glutathione reductase, ascorbate peroxidase, guaiacol peroxidase and superoxide dismutase) were examined in uninfected leaves and in leaves infected with viruses. High accumulation of superoxide and hydrogen peroxide radicals was visualized in infected leaves as a purple discoloration of nitro blue tetrazolium and 3,3'-diaminobenzidine tetrahydrochloride. It was found that the activities of APX and CAT significantly increased in all infected samples compared with non-infected ones. Dynamics of GR and Cu/Zn-SOD activities differed from those of CAT and APX, and slightly increased in stressed samples. Electrophoretic mobility profiling of APX, GPX and CAT isoenzymes was also studied.

ScRALF3, a secreted RALF-like peptide involved in cell-cell communication between the sporophyte and the female gametophyte in a solanaceous species.

Small peptides have been shown to regulate numerous aspects of plant development through cell-cell communication. These signaling events are particularly important during reproduction, regulating gamete development and embryogenesis. Rapid alkalinization factor (RALF)-like genes, a large gene family that encodes secreted peptides, have specific or ubiquitous expression patterns. Previously, five RALF-like genes with potential involvement during reproduction were isolated from Solanum chacoense. Here, we show that ScRALF3 is an important peptide regulator of female gametophyte development. Its expression, which is auxin-inducible, is strictly regulated before and after fertilization. Down-regulation of ScRALF3 expression by RNA interference leads to the production of smaller fruits that produce fewer seeds, due to improper development of the embryo sacs. Defects include loss of embryo sac nuclei polarization, as well as an increase in asynchronous division, accounting for cellular dysfunctions and premature embryo sac development arrest during megagametogenesis. ScRALF3 is expressed in the sporophytic tissue surrounding the embryo sac, the integument and the nucellus, as revealed by in situ hybridization and GUS staining. As expected for a secreted peptide, fluorescence from an ScRALF3-GFP fusion construct is detected throughout the secretory pathway. Therefore, the ScRALF3 secreted peptide may be directly involved in the regulation of multiple aspects of cell-cell communication between the female gametophyte and its surrounding sporophytic tissue during ovule development.

Interstitial telomeric repeats are enriched in the centromeres of chromosomes in Solanum species.

Interstitial telomeric repeats (ITRs) were reported in a number of animal and plant species. Most ITRs are organized as short tandem arrays and are likely evolutionary relics derived from chromosomal rearrangements and DNA repairs. However, megabase-sized ITR arrays were reported in Solanum species. Here, we report a fluorescence in situ hybridization (FISH) survey of ITRs in all representative diploid Solanum species, including potato, tomato, and eggplant. FISH revealed massive amplification of ITRs in the centromeric regions of chromosomes from the Solanum species containing the B and P genomes. A significant proportion of the ITR FISH signals was mapped within the primary constrictions of the pachytene chromosomes of Solanum pinnatisectum (B genome). In addition, some ITR sites overlapped with St49, a satellite repeat enriched in centromeric DNA sequences associated with CENH3 nucleosomes, in both A and B genome Solanum species. These results show that some ITR subfamilies have been amplified and invaded in the functional centromeres of chromosomes in Solanum species.

Differential modulation of photosynthesis, signaling, and transcriptional regulation between tolerant and sensitive tomato genotypes under cold stress.

The wild species Solanum habrochaites is more cold tolerant than the cultivated tomato (S. lycopersicum). To explore the mechanisms underlying cold tolerance of S. habrochaites, seedlings of S. habrochaites LA1777 introgression lines (ILs), as well as the two parents, were evaluated under low temperature (4°C). The IL LA3969 and its donor parent LA1777 were found to be more cold tolerant than the recurrent parent S. lycopersicum LA4024. The differences in physiology and global gene expression between cold-tolerant (LA1777 and LA3969) and -sensitive (LA4024) genotypes under cold stress were further investigated. Comparative transcriptome analysis identified 1613, 1456, and 1523 cold-responsive genes in LA1777, LA3969, and LA4024, respectively. Gene ontology (GO) term enrichment analysis revealed that more GO biological process terms were significantly enriched among the up-regulated genes in the two tolerant genotypes, whereas more biological processes were significantly repressed by cold stress in the sensitive one. A total of 92 genes with significant differential expression between tolerant and sensitive genotypes under cold stress were identified. Among these, many stress-related GO terms were significantly enriched, such as 'response to stimulus' and 'response to stress'. Moreover, GO terms 'response to hormone stimulus', 'response to reactive oxygen species (ROS)', and 'calcium-mediated signaling' were also overrepresented. Several transcripts involved in hormone or ROS homeostasis were also differentially expressed. ROS, hormones, and calcium as signaling molecules may play important roles in regulating gene expression in response to cold stress. Moreover, the expression of various transcription factors, post-translational proteins, metabolic enzymes, and photosynthesis-related genes was also specifically modulated. These specific modifications may play pivotal roles in conferring cold tolerance in tomato. These results not only provide new insights into the molecular mechanisms of cold tolerance in tomato, but also provide potential candidate genes for genetic improvement.

A time course of GFP expression and mRNA stability in pollen tubes following compatible and incompatible pollinations in Solanum chacoense.

The self-incompatibility (SI) reaction in the Solanaceae involves molecular recognition of stylar haplotypes by pollen and is mediated by the S-locus from which a stylar-localized S-RNase and several pollen-localized F-box proteins are expressed. S-RNase activity has been previously shown to be essential for the SI reaction, leading to the hypothesis that pollen rejection in incompatible crosses is due to degradation of pollen RNA. We used pollen expressing the fluorescent marker GFP, driven by the LAT52 promoter, to monitor the accumulation of mRNA and protein in pollen after compatible and incompatible pollinations. We find that GFP mRNA and protein gradually accumulate in pollen tubes until at least 18-h post-pollination and, up to this time, are only slightly more abundant in compatible compared with incompatible crosses. However, between 18- and 24-h post-pollination, pollen tube GFP mRNA and protein levels show a dramatic increase in compatible crosses and either remain constant or decrease in incompatible crosses. In contrast to these molecular correlates, the growth rates of compatible and incompatible pollen tubes begin to differ after 6-h post-pollination. We interpret the changes in growth rate at 6-h post-pollination as the previously described transition from autotrophic to heterotrophic growth. Thus, while pollen rejection is generally considered to result from the cytotoxic effects of S-RNase activity, this time course reveals that a difference in the growth rate of compatible and incompatible pollen appears prior to any marked effects on at least some types of pollen RNA.

Effects of auxins on the production of steroidal alkaloids in rapidly proliferating tissue and cell cultures of Solanum lyratum.

INTRODUCTION: Solanum lyratum, a rare species, is used to treat cancer, tumours and warts. Plant cell and tissue culture of S. lyratum, producing steroidal alkaloids, could be useful supplements to natural sources. OBJECTIVE: To study the production of solanine, solanidine and solasodine by adding auxin-type phytohormones including indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) to cell and callus cultures of S. lyratum. METHODOLOGY: Methanolic extracts were made from callus and cell cultures of S. lyratumand and analysed using RP C18 HPLC with UV detection. RESULTS: 2,4-D-induced calli from roots led to a significant enhancement in solanine production with a value of 4.13 mg/g dry weight (DW). The maximal solanidine and solasodine levels of 6.26 and 7.69 mg/g DW were respectively obtained with IBA- and IAA-treated S. lyratum cells at concentrations of 1 and 5 mg/L. CONCLUSION: Auxins were found to be useful phytohormones for the production of steroidal alkaloids. The callus and cell culture system developed is simple and can hence be a method of production of steroidal alkaloids in S. lyratum and other Solanaceae species.

Benzothiadiazole (BTH) activates sterol pathway and affects vitamin D3 metabolism in Solanum malacoxylon cell cultures.

Benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), a particularly efficient inducer of systemic acquired resistance (SAR), was developed as an immunizing agent to sensitize various crop species against pathogen infections. Recent works highlighted its activating effect on different metabolic pathways, concerning both primary and secondary metabolites. In this study, we investigated the effect of BTH treatment on sterol levels and vitamin D(3) metabolism in Solanum malacoxylon cultures. Calli of S. malacoxylon were incubated in Gamborg B5 liquid medium alone or added with 50 µM BTH for different times (one, two or three cycles of light). Histocytochemical investigations performed on our experimental system using 3,3'-diaminobenzidine (DAB) for hydrogen peroxide (H(2)O(2)) detection and phloroglucinol for lignin staining showed that BTH causes H(2)O(2) accumulation and lignin deposition in treated calli. Gas chromatographic analysis of principal cell membrane sterols (ß-sitosterol, campesterol, stigmasterol) showed that BTH transiently increases their cellular levels. Callus cultures were found to contain also cholesterol, 7-dehydrocholesterol, the putative precursor of vitamin D(3), and the hydroxylated metabolites 25-hydroxyvitamin D(3) [25(OH)D(3)] and 1α,25-dihydroxyvitamin D(3) [1α,25(OH)(2)D(3)]. BTH treatment enhanced 7-dehydrocholesterol while reduced cholesterol. HPLC analysis of sample extracts showed that BTH does not affect the cell content of vitamin D(3), though results of ELISA tests highlighted that this elicitor moderately enhances the levels of 25(OH)D(3) and 1α,25(OH)(2)D(3) metabolites. In conclusion, BTH treatment not only causes cell wall strengthening, a typical plant defence response, as just described in other experimental models, but in the same time increases the cellular level of the main sterols and 7-dehydrocholesterol.

Morphogenesis of complex plant cell shapes: the mechanical role of crystalline cellulose in growing pollen tubes.

Cellulose is the principal component of the load-bearing system in primary plant cell walls. The great resistance to tensile forces of this polysaccharide and its embedding in matrix components make the cell wall a material similar to a fiber composite. In the rapidly growing pollen tube, the amount of cellulose in the cell wall is untypically low. Therefore, we want to investigate whether the load-bearing function of cellulose is nevertheless important for the architecture of this cell. Enzymatic digestion with cellulase and inhibition of cellulose crystal formation with CGA (1-cyclohexyl-5-(2,3,4,5,6-pentafluorophenoxy)-1lambda4,2,4,6-thiatriazin-3-amine) resulted in the formation of tubes with increased diameter in Solanum chacoense and Lilium orientalis when present during germination. In pre-germinated tubes, application of both agents resulted in the transient arrest of growth accompanied by the formation of an apical swelling indicating a role in the mechanical stabilization of this cellular region. Once growth resumed in the presence of cellulase, however, the cell wall in the newly formed tube showed increased amounts of pectins, possibly to compensate for the reduced amount of cellulose. Scanning electron microscopy of pollen tubes subjected to digestion of matrix polysaccharides revealed the mechanical anisotropy of the cell wall. In both Lilium and Solanum, the angle of highest stability revealed by crack formation was significantly below 45 degrees , an indication that in the mature part of the cell cellulose may not the main stress-bearing component against turgor pressure induced tensile stress in circumferential direction.

Phenotypic instability and epigenetic variability in a diploid potato of hybrid origin, Solanum ruiz-lealii.

BACKGROUND: The wild potato Solanum ruiz-lealii Brüch. (2n = 2x = 24), a species of hybrid origin, is endemic to Mendoza province, Argentina. Recurrent flower malformations, which varied among inflorescences of the same plant, were observed in a natural population. These abnormalities could be the result of genomic instabilities, nucleus-cytoplasmic incompatibility or epigenetic changes. To shed some light on their origin, nuclear and mitochondrial DNA of plants with normal and plants with both normal and malformed flowers (from here on designated as plants with normal and plants with abnormal flower phenotypes, respectively) were analyzed by AFLP and restriction analyses, respectively. Also, the wide genome methylation status and the level of methylation of a repetitive sequence were studied by MSAP and Southern blots analyses, respectively. RESULTS: AFLP markers and restriction patterns of mitochondrial DNA did not allow the differentiation of normal from abnormal flower phenotypes. However, methylation patterns of nuclear DNA discriminated normal and abnormal flower phenotypes into two different groups, indicating that abnormal phenotypes have a similar methylation status which, in turn, was different from the methylation patterns of normal phenotypes. The abnormal flower phenotype was obtained by treating a normal plant with 5-Azacytidine, a demethylating agent, giving support to the idea of the role of DNA methylation in the origin of flower abnormalities. In addition, the variability detected for DNA methylation was greater than the detected for nucleotide sequence. CONCLUSION: The epigenetic nature of the observed flower abnormalities is consistent with the results and indicates that in the diploid hybrid studied, natural variation in methylation profiles of anonymous DNA sequences could be of biological significance.

Overview of the phylogenetic relationships of some southern Brazilian species from section Torva and related sections of "spiny Solanum" (Solanum subgenus Leptostemonum, Solanaceae).

One of the major concerns of conservation biology is the knowledge on biodiversity. Many taxa have not yet been described and plant taxonomists are working hard to change this situation. This work presents a taxonomic overview of Solanum section Torva, from South Brazil, which still poorly understood. The section includes species known as "jurubeba" which are of considerable interest because of their pharmacological properties. Despite their higher economic value, it is difficult to identify the "jurubebas" correctly due to their taxonomic problems. A few questions on evolution concerning phylogenetic relationships in this section and other related sections of subgenus Leptostemonum were investigated to clarify the species circumscription and taxonomic issues. Eighty samples were analysed based on sequence variability of the internal transcribed spacers (ITS) of the nuclear ribosomal DNA, as well as the chloroplast intron trnL, trnL-trnF and trnS-trnG spacers. Five different matrixes were analyzed as the basis for a phylogenetic approach. The combined data from the chloroplast analyses formed well-supported trees. Solanum section Torva was proposed as a monophyletic group and it is close to S. melongena, S. jamaicense and S. sisymbriifolium.

Nuclear and cytoplasmic genome composition of Solanum bulbocastanum (+) S. tuberosum somatic hybrids.

Somatic hybrids between the wild incongruent species Solanum bulbocastanum (2n = 2x = 24) and S. tuberosum haploids (2n = 2x = 24) have been characterized for their nuclear and cytoplasmic genome composition. Cytologic observations revealed the recovery of 8 (near-)tetraploid and 3 hexaploid somatic hybrids. Multicolor genomic in situ hybridization (GISH) analysis was carried out to study the genomic dosage of the parental species in 5 somatic hybrids with different ploidy. The GISH procedure used was effective in discriminating parental genomes in the hybrids; most chromosomes were unambiguously colored. Two (near-)tetraploid somatic hybrids showed the expected 2:2 cultivated-to-wild genomic dosage; 2 hexaploids revealed a 4:2 cultivated-to-wild genomic dosage, and 1 hexaploid had a 2:4 cultivated-to-wild genomic dosage. Characterization of hybrid cytoplasmic genomes was performed using gene-specific primers that detected polymorphisms between the fusion parents in the intergenic regions. The analysis showed that most of the somatic hybrids inherited the plastidial and mitochondrial DNA of the cultivated parent. A few hybrids, with a rearranged mitochondrial genome (showing fragments derived from both parents), were also identified. These results confirmed the potential of somatic hybridization in producing new variability for genetic studies and breeding.

Production and characterization of arboreous and fertile Solanum melongena + Solanum marginatum somatic hybrid plants.

In crop plants the shift from being annuals to perennials may allow future agricultural systems requiring less energy inputs. The practicability of this was tested for Solanum melongena. Leaf protoplasts of S. melongena (2n = 2x = 24) and one of the related arborescent species Solanum marginatum (2n = 2x = 24) were electrofused and fertile somatic hybrids with arborescent habit regenerated. The magnetic cell sorter (MACS) technique was used for the selection of heterokaryons. The hybrid nature of 18 regenerated plants was assessed on the banding patterns generated by inter-simple sequence repeat PCR. When taken to maturity in the greenhouse, hybrids grew more vigorously compared to the parental species. Their morphological traits were intermediate between those of S. melongena and S. marginatum. Hybrids flowered and produced an average of 85% stainable viable pollen and fertile fruits. The somatic hybrids were maintained in the greenhouse for more than 3 years and continued to produce flowers developing into two types of fruits with plentiful seeds. Fruits were either striated green containing non-germinable seeds or yellow with fully germinable seeds. Their S(1) progenies showed common features with S(0) hybrids, including fertility and arborescent habit. Cytologically, somatic hybrids exhibited the expected chromosome number of 2n = 4x = 48, while chromosome pairing during microsporogenesis was associated with a low frequency of intergenomic pairing. It is concluded that an arborescent perennial species has been obtained by somatic hybridization. The usefulness of this species per se or in eggplant breeding will depend not only on the transmission of the arborescent habit to cultivated eggplant varieties, but also on the variability that should be created from backcrossing the S. melongena + S. marginatum hybrids to S. melongena.

Cryopreservation of cultivated and wild potato varieties by droplet vitrification: effect of subculture of mother-plants and of preculture of shoot tips.

In this paper, we studied the effect of subculture of mother-plants and of preculture of shoot tips of two potato varieties (Dejima, cultivated and STN13, wild) cryopreserved using the droplet-vitrification technique. The subculture conditions (light intensity, aeration and planting density) significantly affected survival of both non-cryopreserved and cryopreserved shoot-tips in both varieties. The subculture duration and the position of the shoot tips on the axis of the in vitro plantlets had a significant (P<0.0001) effect on survival of cryopreserved shoot tips. The optimal subculture duration was 7 and 5 weeks and the optimal size of shoot tips was 1.5-2.0 and 1.0-1.5 mm for var. Dejima and STN13, respectively. Survival of cryopreserved shoot tips was influenced by the sucrose concentration in the preculture medium and the preculture duration. The highest survival of cryopreserved shoot tips was observed after preculture with 0.3 M sucrose for 8 h followed by 0.7 M sucrose for 18 h. These results indicate that the parameters of the subculture of mother-plants and of preculture of shoot tips should be carefully optimized, especially in the case of wild species.

Cryopreservation of potato cultivated varieties and wild species: critical factors in droplet vitrification.

The applicability of cryopreservation protocols to a broad range of genotypes is a key issue for genebanks. We tried to identify the critical factors causing differences in survival of cryopreserved shoot tips using potato varieties coming from cultivated and wild species. The droplet-vitrification method, a combination of droplet-freezing and solution-based vitrification, was selected from several protocols. High survival after freezing was observed after dehydration with PVS2 for 20 min, cooling shoot tips placed in a droplet of PVS2 solution on aluminum foil strips by immersing the foil strips in liquid nitrogen, warming them by plunging the foil strips into a 0.8 M sucrose solution (at 40 degrees C) for 30 s and unloading in 0.8 M sucrose for 30 min. This optimized protocol was successfully applied to 12 accessions with survival ranging between 64.0 and 94.4%.