Micropropagation and genetic transformation of <Emphasis Type="Italic">Tylophora indica</Emphasis> (Burm. f.) Merr.: a review

Key message

This review provides an in-depth and comprehensive overview of the in vitro culture of Tylophora species, which have medicinal properties.

Abstract

Tylophora indica (Burm. f.) Merr. is a climbing perennial vine with medicinal properties. The tissue culture and genetic transformation of T. indica, which has been extensively studied, is reviewed. Micropropagation using nodal explants has been reported in 25 % of all publications. Leaf explants from field-grown plants has been the explant of choice of independent research groups, which reported direct and callus-mediated organogenesis as well as callus-mediated somatic embryogenesis. Protoplast-mediated regeneration and callus-mediated shoot organogenesis has also been reported from stem explants, and to a lesser degree from root explants of micropropagated plants in vitro. Recent studies that used HPLC confirmed the potential of micropropagated plants to synthesize the major T. indica alkaloid tylophorine prior to and after transfer to field conditions. The genetic integrity of callus-regenerated plants was confirmed by RAPD in a few reports. Tissue culture is an essential base for genetic transformation studies. Hairy roots and transgenic T. indica plants have been shown to accumulate tylophorine suggesting that in vitro biology and transgenic methods are viable ways of clonally producing valuable germplasm and mass producing compounds of commercial value. Further studies that investigate the factors affecting the biosynthesis of Tylophora alkaloids and other secondary metabolites need to be conducted using non-transformed as well as transformed cell and organ cultures.

     

Taxonomic revision of the genus <Emphasis Type="Italic">Catalpa</Emphasis> (Bignoniaceae)

A taxonomic revision of Catalpa (Bignoiaceae), a genus of perennial trees frequently used in horticulture as garden and street trees, is provided. Eight natural species and two hybrid species are recognized, four in sect. Catalpa, four in sect. Macrocatalpa, and two hybrid species in sect. Catalpa. Although C. punctata has been used for one of the tropical species, C. macrocarpa is the correct scientific name. Catalpa tibetica is synonymous with C. bignonioides, C. fargesii with C. bungei, and C. obovata with C. macrocarpa. Lectotypes are designated for: Bignonia cassinoides, Bignonia longisiliqua, Bignonia longissima, Catalpa Walter, Catalpa subsect. Corymbosae, Catalpa bignonioides var. kaempferi, Catalpa bungei, Catalpa bungei var. heterophylla, Catalpa bungei var. intermedia, Catalpa domingensis, Catalpa fargesii, Catalpa henryi, Catalpa ×hybrida, Catalpa ovata var. flavescens, Catalpa punctata var. lepidota, Catalpa purpurea, Catalpa syringifolia var. pulverulenta, Catalpa sutchuensis, Catalpa ×teasii, and Cumbulu. Second-step lectotypes are designated for: Catalpa duclouxii, Catalpa ekmaniana, Catalpa oblongata, Catalpa obovata, and Catalpa ovata. Neotypes are designated for: Bignonia triloba, Catalpa aureovittata, Catalpa bignonioides var. variegata, Catalpa ×erubescens, Catalpa ×erubescens f. purpurea, Catalpa ×galleana, Catalpa ×hybrida var. atropurpurea, Catalpa japonica, Catalpa syringifolia var. aurea, Catalpa syringifolia var. koehnei, Catalpa syringifolia var. nana, Catalpa ×teasiana, and Catalpa umbraculifera.     

Four mononuclear platinum(II) complexes: synthesis,DNA/BSA binding,DNA cleavage and cytotoxicity

Four new platinum(II) complexes: Pt^II L1·H₂O (C1, H₂ L1 = C₂₀H₁₆N₂O₂), Pt^II L2Cl₂ (C2, L2 = C₂₂H₁₆N₂O₂), Pt^II L3Cl₂·H₂O (C3, L3 = C₂₀H₁₆N₂), Pt^II L4Cl₂·0.4H₂O (C4, L4 = C₁₈H₁₄N₄) have been synthesized and characterized by using various physico-chemical techniques. The binding interaction of the four platinum(II) complexes C1–C4 with calf thymus (CT)-DNA has been investigated by UV–Vis and fluorescence emission spectrometry. The apparent binding constant (K _app) values follow the order: C3 > C1 > C2 > C4. In addition, fluorescence spectrometry of bovine serum albumin (BSA) with the four platinum(II) complexes C1–C4 showed that the quenching mechanism might be a static quenching procedure. For C1–C4, the number of binding sites was about one for BSA and the binding constants follow the order: C3 (7.08 × 10⁵M^?1) > C1 (2.82 × 10⁵M^?1) > C2 (0.85 × 10⁵M^?1) > C4 (0.15 × 10⁵M^?1). With the single condition change such as absence of an external agent, the DNA cleavage abilities of C3 exhibit remarkable changes. In addition, the cytotoxicity of C3 in vitro on tumor cells lines (MCF-7, HepG2 and HT29) were examined by MTT and showed better antitumor effects on the tested cells.     

Synthesis,X-ray crystal structure,DNA/BSA binding,DNA cleavage and cytotoxicity studies of phenanthroline based copper(II)/zinc(II) complexes

Research on copper^II 1,10-phenanththroline (phen) derivatives continues to attract interest in the context of structure and biological properties. In this paper, two metal complexes [Cu₂(phen)₂(μ-Cl)₂]Cl₂ (1), [Zn(phen)₂(H₂O)Cl]Cl·4H₂O (2) were synthesized and characterized. The crystal structures of 1 and 2 were determined by X-ray diffraction. In order to investigate the biological properties of the prepared complexes, spectroscopic and biological studies were performed. Results of X-ray diffraction showed that 1 and 2 form two types of crystal structures in a given system: dinuclear and mono-nuclear complex. The preliminary study on the DNA cleavage activity has shown that 1 under study behaved as the chemical nucleases. The DNA binding interaction of 1 & 2 with CT-DNA has been investigated by UV–Visible and fluorescence emission spectrometry and the apparent binding constant (K _app) values are 5.1 × 10⁴ and 1.2 × 10⁴ M^?1, respectively. In addition, fluorescence spectrometry of bovine serum albumin (BSA) with 1 & 2 showed that the quenching mechanism might be a static quenching procedure with one binding sites for BSA. In addition, the cytotoxicity of 1 in vitro on tumor cells lines (MCF-7, HepG2 and HT29) was examined by MTT and showed better antitumor effect on the tested cells.     

Control of brown patch (<Emphasis Type="Italic">Rhizoctonia solani</Emphasis>) in tall fescue (<Emphasis Type="Italic">Festuca arundinacea</Emphasis> Schreb.) by host induced gene silencing

Key message

Transgenic tall fescue plants expressing RNAi constructs of essential genes of Rhizoctonia solani were resistant to R. solani.

Abstract

Tall fescue (Festuca arundinacea Schreb.) is an important turf and forage grass species widely used for home lawns and on golf courses in North Carolina and other transition zone states in the US. The most serious and frequently occurring disease of tall fescue is brown patch, caused by a basidiomycete fungus, Rhizoctonia solani. This research demonstrates resistance to brown patch disease achieved by the application of host induced gene silencing. We transformed tall fescue with RNAi constructs of four experimentally determined “essential” genes from R. solani (including genes encoding RNA polymerase, importin beta-1 subunit, Cohesin complex subunit Psm1, and a ubiquitin E3 ligase) to suppress expression of those genes inside the fungus and thus inhibit fungal infection. Four gene constructs were tested, and 19 transgenic plants were obtained, among which 12 plants had detectable accumulation of siRNAs of the target genes. In inoculation tests, six plants displayed significantly improved resistance against R. solani. Lesion size was reduced by as much as 90 %. Plants without RNAi accumulation did not show resistance. To our knowledge, this is the first case that RNAi constructs of pathogen genes introduced into a host plant can confer resistance against a necrotrophic fungus.

     

Growth and nodulation in <Emphasis Type="Italic">Alnus sieboldiana</Emphasis> in response to <Emphasis Type="Italic">Frankia</Emphasis> inoculation and nitrogen treatments

Key message

We investigated a Frankia – Alnus sieboldiana symbiosis, including the minimum inoculum dose for constant nodulation, the period of time to nodulation after inoculation, and the effects of N on nodulation.

Abstract

Frankia is a nitrogen-fixing actinomycete that forms root nodules in some dicotyledonous plants, which are called actinorhizal. We studied nodule formation in Alnus sieboldiana, an actinorhizal plant, after inoculation with a Frankia isolate to establish techniques for Frankia inoculation and the cultivation of inoculated plants. Root nodules formed on seedlings of A. sieboldiana by 2 weeks after inoculation, and N₂ fixation measured by acetylene reduction activity started 3 weeks after inoculation. Nodulation was observed after inoculation with a Frankia isolate at 0.001 μL packed cell volume (pcv). The number of nodules formed on the seedlings inoculated with Frankia at more than 0.05 μL pcv was not significantly different. Nodule development and N₂ fixation were reduced when inoculated seedlings were treated weekly with 15 mM NH₄NO₃-N. In contrast, treatment with 3.75 or 0.9375 mM NH₄NO₃-N did not inhibit nodule development or N₂ fixation of inoculated seedlings by 15 weeks of N treatment.

     

Genetic composition of interspecific potato somatic hybrids and autofused 4<Emphasis Type="Italic">x</Emphasis> plants evaluated by DArT and cytoplasmic DNA markers

Key message

Using DArT analysis, we demonstrated that all Solanum × michoacanum (+) S. tuberosum somatic hybrids contained all parental chromosomes. However, from 13.9 to 29.6 % of the markers from both parents were lost in the hybrids.

Abstract

Somatic hybrids are an interesting material for research of nucleus-cytoplasm interaction and sources of new nuclear and cytoplasmic combinations. Analyses of genomes of somatic hybrids are essential for studies on genome compatibility between species, its evolution and are important for their efficient exploitation. Diversity array technology (DArT) permits analysis of the composition of nuclear DNA of somatic hybrids. The nuclear genome compositions of 97 Solanum × michoacanum (+) S. tuberosum [mch (+) tbr] somatic hybrids from five fusion combinations and 11 autofused 4x mch were analyzed for the first time based on DArT markers. Out of 5358 DArT markers generated in a single assay, greater than 2000 markers were polymorphic between parents, of which more than 1500 have a known chromosomal location on potato genetic or physical map. DArT markers were distributed along the entire length of 12 chromosomes. We noticed elimination of markers of wild and tbr fusion components. The nuclear genome of individual somatic hybrids was diversified. Mch is a source of resistance to Phytophthora infestans. From 97 mch (+) tbr somatic hybrids, two hybrids and all 11 autofused 4x mch were resistant to P. infestans. The analysis of the structure of particular hybrids’ chromosomes indicated the presence of markers from both parental genomes as well as missing markers spread along the full length of the chromosome. Markers specific to chloroplast DNA and mitochondrial DNA were used for analysis of changes within the organellar genomes of somatic hybrids. Random and non-random segregations of organellar DNA were noted.

     

Significant increase of oleic acid level in the wild species <Emphasis Type="Italic">Lepidium campestre</Emphasis> through direct gene silencing

Key message

Simultaneous RNAi silencing of the FAD2 and FAE1 genes in the wild species Lepidium campestre improved the oil quality with 80 % oleic acid content compared to 11 % in wildtype.

Abstract

Field cress (Lepidium campestre) is a wild biennial species within the Brassicaceae family with desirable agronomic traits, thus being a good candidate for domestication into a new oilseed and catch crop. However, it has agronomic traits that need to be improved before it can become an economically viable species. One of such traits is the seed oil composition, which is not desirable either for food use or for industrial applications. In this study, we have, through metabolic engineering, altered the seed oil composition in field cress into a premium oil for food processing, industrial, or chemical industrial applications. Through seed-specific RNAi silencing of the field cress fatty acid desaturase 2 (FAD2) and fatty acid elongase 1 (FAE1) genes, we have obtained transgenic lines with an oleic acid content increased from 11 % in the wildtype to over 80 %. Moreover, the oxidatively unstable linolenic acid was decreased from 40.4 to 2.6 %, and the unhealthy erucic acid was reduced from 20.3 to 0.1 %. The high oleic acid trait has been kept stable for three generations. This shows the possibility to use field cress as a platform for genetic engineering of oil compositions tailor-made for its end uses.

     

Revision of the <Emphasis Type="Italic">Rhynchospora glomerata</Emphasis> species complex,focusing on the taxonomic status of <Emphasis Type="Italic">R. leptocarpa</Emphasis> (Cyperaceae)

Rhynchospora glomerata and its closest relatives comprise a group of beakesedges widespread and frequent in much of North America. The classification of the R. glomerata complex remains unresolved and controversial. The goals of this study are to determine the number of taxa in the complex and their ranks, and identify their best diagnostic characters. Measurements of eight characters from each of 101 specimens from throughout the geographic range of the complex furnished data for morphometric analyses. These analyses reveal the R. glomerata complex contains three species and no infraspecific taxa: R. capitellata, R. glomerata, and R. leptocarpa. We detected 10 validly published basionyms in the complex, five of which required lectotypification. Accordingly, we designated lectotypes for R. glomerata var. discutiens, R. glomerata var. minor, R. glomerata var. paniculata, and R. glomerata var. robustior, and the second-step lectotype for R. capitellata var. controversa.     

Characterization of morphology and resistance to <Emphasis Type="Italic">Blumeria graminis</Emphasis> of winter triticale monosomic addition lines with chromosome 2D of <Emphasis Type="Italic">Aegilops</Emphasis><Emphasis Type="Italic">tauschii</Emphasis>

Key message

Allocation of the chromosome 2D of Ae. tauschii in triticale background resulted in changes of its organization, what is related to varied expression of genes determining agronomically important traits.

Abstract

Monosomic alien addition lines (MAALs) are crucial for transfer of genes from wild relatives into cultivated varieties. This kind of genetic stocks is used for physical mapping of specific chromosomes and analyzing alien genes expression. The main aim of our study is to improve hexaploid triticale by transferring D-genome chromatin from Aegilops tauschii × Secale cereale (2n = 4x = 28, DDRR). In this paper, we demonstrate the molecular cytogenetics analysis and SSR markers screening combined with phenotype analysis and evaluation of powdery mildew infection of triticale monosomic addition lines carrying chromosome 2D of Ae. tauschii. We confirmed the inheritance of chromosome 2D from the BC₂F₄ to the BC₂F₆ generation of triticale hybrids. Moreover, we unveiled a high variable region on the short arm of chromosome 2D, where chromosome rearrangements were mapped. These events had direct influence on plant height of hybrids what might be connected with changes at Rht8 loci. We obtained 20 semi-dwarf plants of BC₂F₆ generation carrying 2D chromosome with the powdery mildew resistance, without changes in spike morphology, which can be used in the triticale breeding programs.

     

Rapid and efficient <Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation of sorghum (<Emphasis Type="Italic">Sorghum bicolor</Emphasis>) employing standard binary vectors and <Emphasis Type="Italic">bar</Emphasis> gene as a selectable marker

Key message

A rapid and efficient Agrobacterium -mediated transformation system in sorghum has been developed employing standard binary vectors and bar gene as a selectable marker.

Abstract

Sorghum (Sorghum bicolor) is an important food and biofuel crop worldwide, for which improvements in genetic transformation are needed to study its biology and facilitate agronomic and commercial improvement. Here, we report optimization of regeneration and transformation of public sorghum genotype P898012 using standard binary vectors and bar gene as a selectable marker. The tissue culture regeneration time frame has been reduced to 7–12 weeks with a yield of over 18 plants per callus, and the optimized transformation system employing Agrobacterium tumefaciens strain AGL1 and the bar with a MAS promoter achieved an average frequency over 14 %. Of randomly analyzed independent transgenic events, 40–50 % carry single copy of integrated T-DNA. Some independent transgenic events were derived from the same embryogenic callus lines, but a 3:1 Mendelian segregation ratio was found in all transgenic events with single copy as estimated by Southern blots. The system described here should facilitate studies of sorghum biology and agronomic improvement.

     

Differential alkaloid profile in <Emphasis Type="Italic">Uncaria tomentosa</Emphasis> micropropagated plantlets and root cultures

The alkaloids of Uncaria tomentosa micropropagated plantlets and root cultures were isolated and identified by NMR and mass spectrometry. Plantlets yielded pteropodine (1), isopteropodine (2), mitraphylline (3), isomitraphylline (4), uncarine F (5), speciophylline (6), rhynchophylline (7) and isorhynchophylline (8). In plantlets growing under continuous light, tetracyclic alkaloids 7 and 8 decreased from 20 ± 1.8 at 2 months to 2.2 ± 0.33 mg/g dry wt at 6 months, while the pentacyclic alkaloids 1–4 increased from 7.7 ± 1.4 to 15 ± 0.05 mg/g dry wt, supporting their biogenetic conversion. Micropropagated plantlets produced four times more alkaloids (27.6 ± 3.1 mg/g dry wt) than greenhouse plants. Plantlet roots yielded 3, 4, 8 and the glucoindole alkaloids 3α-dihydrocadambine (9) and dolichantoside (10), the last one not previously found in Uncaria.     

DNA sequence-specific ligands: XVI. Series of the DBP(<Emphasis Type="Italic">n</Emphasis>) fluorescent dimeric bisbenzimidazoles with 1,4-piperazine-containing linkers

A novel series of the DBP(n) fluorescent symmetric dimeric bisbenzimidazoles in which the bisbenzimidazole fragments were attached to an oligomeric linker with the 1,4-piperazine residue in its center were prepared. The DBP(n) molecules were distinguished by the number of methylene groups n (where n = 1, 2, 3, 4) in the linker. The DBP(n) synthesis was based on a condensation of the monomeric bisbenzimidazole (MB) with 1,4-piperazinedialkylcarbonic acids. The ability of the DBP(n) dimeric bisbenzimidazoles to form complexes with the double-stranded DNA was demonstrated by a complex of physicochemical methods, including spectroscopy in the visual UV-area, circular dichroism (CD), and fluorescence. The DBP(1–4) molecules were localized in the DNA minor groove by the CD method with the use of cholesteric liquid-crystalline dispersions (CLCD) of the double-stranded DNA. The DBP(n) dimeric bisbenzimidazoles were easily soluble in water, penetrated through cellular and nuclear membranes, and stained DNA in living cells distinct from the previously synthesized DB(n) series.     

High salinity helps the halophyte <Emphasis Type="Italic">Sesuvium portulacastrum</Emphasis> in defense against Cd toxicity by maintaining redox balance and photosynthesis

Main conclusion

NaCl alleviates Cd toxicity in Sesvium portulacastrum by maintaining plant water status and redox balance, protecting chloroplasts structure and inducing some potential Cd ²⁺ chelators as GSH and proline. It has been demonstrated that NaCl alleviates Cd-induced growth inhibition in the halophyte Sesuvium portulacastrum. However, the processes that mediate this effect are still unclear. In this work we combined physiological, biochemical and ultrastructural studies to highlight the effects of salt on the redox balance and photosynthesis in Cd-stressed plants. Seedlings were exposed to different Cd concentrations (0, 25 and 50 µM Cd) combined with low (0.09 mM) (LS), or high (200 mM) NaCl (HS) in hydroponic culture. Plant–water relations, photosynthesis rate, leaf gas exchange, chlorophyll fluorescence, chloroplast ultrastructure, and proline and glutathione concentrations were analyzed after 1 month of treatment. In addition, the endogenous levels of stress-related hormones were determined in plants subjected to 25 µM Cd combined with both NaCl concentrations. In plants with low salt supply (LS), Cd reduced growth, induced plant dehydration, disrupted chloroplast structure and functioning, decreased net CO₂ assimilation rate (A) and transpiration rate (E), inhibited the maximum potential quantum efficiency (Fv/Fm) and the quantum yield efficiency (Φ _PSII) of PSII, and enhanced the non-photochemical quenching (NPQ). The addition of 200 mM NaCl (HS) to the Cd-containing medium culture significantly mitigated Cd phytotoxicity. Hence, even at similar internal Cd concentrations, HS-Cd plants were less affected by Cd than LS-Cd ones. Hence, 200 mM NaCl significantly alleviates Cd-induced toxicity symptoms, growth inhibition, and photosynthesis disturbances. The cell ultrastructure was better preserved in HS-Cd plants but affected in LS-Cd plants. The HS-Cd plants showed also higher concentrations of reduced glutathione (GSH), proline and jasmonic acid (JA) than the LS-Cd plants. However, under LS-Cd conditions, plants maintained higher concentration of salicylic acid (SA) and abscisic acid (ABA) than the HS-Cd ones. We conclude that in S. portulacastrum alleviation of Cd toxicity by NaCl is related to the modification of GSH and proline contents as well as stress hormone levels thus protecting redox balance and photosynthesis.

     

Over-expression of AQUA1 in <Emphasis Type="Italic">Populus alba</Emphasis> Villafranca clone increases relative growth rate and water use efficiency,under Zn excess condition

Key message

Transgenic Populus alba over-expressing a TIP aquaporin ( aqua1) showed a higher growth rate under Zn excess, suggesting that aqua1 could be involved in water homeostasis, rather than in Zn homeostasis.

Abstract

Populus is the internationally accepted model for physiological and developmental studies of tree traits under stress. In plants, aquaporins facilitate and regulate the diffusion of water, however, few poplar aquaporins have been characterized to date. In this study, we reported for the first time an in vivo characterization of Populus alba clone Villafranca transgenic plants over-expressing a TIP aquaporin (aqua1) of P. x euramericana clone I-214. An AQUA1:GFP chimeric construct, over-expressed in P. alba Villafranca clones, shows a cytoplasmic localization in roots, and it localizes in guard cells in leaves. When over-expressed in transgenic plants, aqua1 confers a higher growth rate compared to wild-type (wt) plants, without affecting chlorophyll accumulation, relative water content (RWC), and fluorescence performances, but increasing the intrinsic Transpiration Efficiency. In response to Zn (1 mM), transgenic lines did not show a significant increase in Zn accumulation as compared to wt plants, even though the over-expression of this gene confers higher tolerance in root tissues. These results suggest that, in poplar plants, this gene could be principally involved in regulation of water homeostasis and biomass production, rather than in Zn homeostasis.

     

Fine mapping of a male sterility gene <Emphasis Type="Italic">ms</Emphasis>-<Emphasis Type="Italic">3</Emphasis> in a novel cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) mutant

Key message

The cucumber male sterility gene ms - 3 was fine mapped in a 76 kb region harboring an MMD1 -like gene Csa3M006660 that may be responsible for the male sterile in cucumber.

Abstract

A cucumber (Cucumis sativus L.) male sterile mutant (ms-3) in an advanced-generation inbred line was identified, and genetic analysis revealed that the male sterility trait was controlled by a recessive nuclear gene, ms-3, which was stably inherited. Histological studies suggested that the main cause of the male sterility was defective microsporogenesis, resulting in no tetrad or microspores being formed. Bulked segregant analysis (BSA) and genotyping of an F₂ population of 2553 individuals were employed used to fine map ms-3, which was delimited to a 76 Kb region. In this region, a single non-synonymous SNP was found in the Csa3M006660 gene locus, which was predicted to result in an amino acid change. Quantitative RT-PCR analysis of Csa3M006660 was consistent with the fact that it plays a role in the early development of cucumber pollen. The protein encoded by Csa3M006660 is predicted to be homeodomain (PHD) finger protein, and the high degree of sequence conservation with homologs from a range of plant species further suggested the importance of the ms-3 non-synonymous mutation. The data presented here provide support for Csa3M006660 as the most likely candidate gene for Ms-3.

     

Development of <Emphasis Type="Italic">Brassica oleracea</Emphasis>-<Emphasis Type="Italic">nigra</Emphasis> monosomic alien addition lines: genotypic,cytological and morphological analyses

Key message

We report the development and characterization of Brassica oleracea - nigra monosomic alien addition lines (MAALs) to dissect the Brassica B genome.

Abstract

Brassica nigra (2n = 16, BB) represents the diploid Brassica B genome which carries many useful genes and traits for breeding but received limited studies. To dissect the B genome from B. nigra, the triploid F₁ hybrid (2n = 26, CCB) obtained previously from the cross B. oleracea var. alboglabra (2n = 18, CC) × B. nigra was used as the maternal parent and backcrossed successively to parental B. oleracea. The progenies in BC₁ to BC₃ generations were analyzed by the methods of FISH and SSR markers to screen the monosomic alien addition lines (MAALs) with each of eight different B-genome chromosomes added to C genome (2n = 19, CC + 1B_1?8), and seven different MAALs were established, except for the one with chromosome B2 which existed in one triple addition. Most of these MAALs were distinguishable morphologically from each other, as they expressed the characters from B. nigra differently and at variable extents. The alien chromosome remained unpaired as a univalent in 86.24% pollen mother cells at diakinesis or metaphase I, and formed a trivalent with two C-genome chromosomes in 13.76% cells. Transmission frequency of all the added chromosomes was far higher through the ovules (averagely 14.40%) than the pollen (2.64%). The B1, B4 and B5 chromosomes were transmitted by female at much higher rates (22.38–30.00%) than the other four (B3, B6, B7, B8) (5.04–8.42%). The MAALs should be valuable for exploiting the genome structure and evolution of B. nigra.

     

Genetic diversity and population structure of <Emphasis Type="Italic">Melia azedarach</Emphasis> in North-Western Plains of India

Key message

Genetic structure among M. azedarach populations was detected and two subpopulations were present among them. A significant ‘isolation by distance’ was found in M. azedarach population in North-Western Plains of India.

Abstract

Melia azedarach is an important forest tree with pharmaceutical, insecticidal, pesticidal, and commercial significance. It is a good reforestation tree because of its fast growth and drought hardy nature. Genetic variation in a species allows itself to adapt, evolve and respond to environmental stress. It provides the basis for survival of a species and critically influences its evolutionary potential. Assessment of genetic diversity is necessary for improvement and conservation of a species. For this, microsatellite markers are of particular interest given the attributes like co-dominance, reproducibility, hyper variability and abundance throughout the genome. In the present study, we analyzed the genetic diversity and population structure of M. azedarach, an ecologically imperative species growing in the North-Western Plains of India. We developed 43 microsatellite markers, of which 20 were subsequently employed for analysis of diversity and population structure among 33 populations encompassing 318 genotypes representing North-Western Plains of India. A moderate level of diversity (Na = 5.1, Ho = 0.506, He = 0.712, I = 1.386) was assessed. The highest value of ΔK estimated using STRUCTURE indicated 2 subpopulations (K = 2). AMOVA exhibited 73 % variation within populations and 12 % variation was found among regions. Significant positive correlation between geographical and genetic distance was found (Rxy = 0.365, P = 0.010). The present study lays a foundation on a better understanding of genetic dynamics of the species and reveals its diversity and population structure in North-Western Plains of India.