Cybrid/hybrid plants regenerated from somatic fusions between male sterile Satsuma mandarin and seedy tangelos

Somatic hybridization provides an alternative for transferring mitochondria-encoded cytoplasmic male sterility (CMS). Herein, symmetric protoplast electrofusion was conducted between embryogenic callus protoplasts of Citrus unshiu Marc. cv. Guoqing No. 1 (G1), a CMS cultivar, and mesophyll-derived protoplasts of seedy ‘Page’ tangelo [C. reticulata Blanco × (C. reticulata Blanco × C. paradisi Macf.)] or ‘Nova’ tangelo [C. reticulata Blanco × (C. reticulata Blanco × C. paradisi Macf.)], to transfer CMS trait. Flow cytometry analysis showed that 14 plants recovered from G1 + ‘Page’ tangelo that displayed typical morphological character of ‘Page’ were diploid, and 6 plants regenerated from G1 + ‘Nova’ tangelo were tetraploid. Genetic compositions of regenerated plants from the two fusions were determined by SSR, CAPS and chloroplast-SSR analysis. Cybrid nature of diploids from G1 + ‘Page’ tangelo with nuclear DNA from ‘Page’, mitochondrial DNA (mtDNA) from the G1 and chloroplast DNA (cpDNA) derived from either parent was confirmed. Tetraploid plants from G1 + ‘Nova’ tangelo were identified as somatic hybrids with random cpDNA inheritance. The regenerated cybrid and hybrid plants hold great potential for Citrus seedless breeding at diploid or triploid levels.     

Aneuploid strawberry (2n = 8x + 2 = 58) was developed from homozygous unreduced gamete (8x) produced by second division restitution in pollen

Unreduced gamete formation is significant in the evolutionary development of complex polyploidy series found in wild strawberry, genus Fragaria (Rosaceae). Also, it is important for genetics and breeding in strawberry plants to elucidate the mechanism of unreduced gamete formation. The objective of this study was to search for ploidy anomalies resulting from artificial diploid × octoploid crosses, and examine the mechanism through which these unreduced gametes were produced. Five everbearing cultivars of Fragaria vesca L. diploid (2n = 2x = 14) were crossed with pollen from six June-bearing cultivars of Fragaria × ananassa Duch., octoploid (2n = 8x = 56). A total of 3000 mature seeds, 100 from each of the 30 parental combinations were sown at 23 °C/20 °C (day/night) under artificial lighting with a 16 h day. The seedlings were transplanted to pots and grown in a greenhouse. Reproductive and morphological observations, flow cytometry analyses, chromosome counts and DNA analyses using CAPS markers were performed to identify the genetic background of the offspring. Most of the seed (79%) did not germinate or died soon after germination. Of the seedlings produced, 7% seemed to be pure F. vesca based on morphological characteristics, flow cytometry analyses and chromosome counts; 14% were pentaploids (2n = 5x = 35), 0.1% were hexaploids (2n = 6x = 42), and 0.03% (one individual) was aneuploid (2n = 8x + 2 = 58). Electrophoresis banding patterns obtained by CAPS marker analysis were heterozygotic in the 8x pollen parent but homozygotic in the aneuploid progeny. Judging from the chromosome counts and the CAPS marker analysis, the aneuploid was the result of a homozygous unreduced pollen grain (8x) crossed with an incomplete chromosome compliment from the egg. Because of the homozygosity, the unreduced male gamete must have been derived from second division restitution (SDR) in the octoploid pollen parent.     

Characterization of progenies derived from pollination of pomegranate cv. Malase-Tourshe-Saveh using fruit traits and RAPD molecular marker

Fruit traits and molecular markers (RAPD) were used to survey genetic similarities and inheritance pattern of offspring, derived from self- and open pollination of pomegranate cv. Malase-Tourshe-Saveh (MTS) as well as progenies derived from cross between ‘MTS’ and ‘Narm-Daneh’ (ND) a soft-seed cultivar in the present study. Clustering based on fruit traits, divided the accessions firstly into two major groups, sweets and sour or sweet–sours. Members of sub-clusters were different in fruit characters, and seed softness also was affecting the grouping of individuals. Offspring of ‘MTS’ × ’ND’ showed somehow seed softness with varying degrees compared to other individuals. In RAPD analysis, by using 26 polymorphic primers, 325 fragments were produced from 39 individuals, among which 70 reproducible, polymorphic bands were scored for data analysis. NTsys and Bootstrap software were used for RAPD data analysis and respective dendrogram depicted by Jaccard's similarity coefficients using UPGMA method. The similarity coefficients were ranging from 0.2 to 0.94 and the lowest was obtained between pollen parent (ND cv.) and a genotype from open pollination of MTS cultivar. The highest similarity coefficient (0.94) was observed between two offspring both from self-pollination of MTS cultivar. In corresponding dendrogram, pollen parent was separated from other genotypes and laid individually in a sub-cluster, while the mother plant clustered with its progenies. In addition, some marker–trait associations were observed, especially for seed softness.     

ISSR polymorphism in Indian wild orange (Citrus indica Tanaka,Rutaceae) and related wild species in North-east India

Inter simple sequence repeats (ISSR) polymorphism in Citrus indica Tanaka (Rutaceae), an endemic and threatened wild species, was examined along with three other closely related wild taxa (C. medica L., C. latipes (Swingle) Tanaka, and C. sp. ‘Memang athur’) by analyzing 53 representative accessions sampled from North-east India. Jaccard's similarity values among 53 accessions of Citrus ranged from 0.46 to 0.97 (average = 0.75). Genetic similarity values among all the 34 accessions of C. indica were found in the range of 0.82 to 0.97 with an average of 0.90. Heterozygosity (Ht = 0.123) and Shannon's information index (I = 0.188) values estimated for C. indica revealed significantly low level of genetic variation within the species. UPGMA dendrogram grouped all 53 accessions of Citrus into four major clusters: Cluster I – C. latipes; Cluster II – C. medica; Cluster III – ‘Memang athur’ and Cluster IV – C. indica. The dendrogram placed all the 34 accessions of C. indica in five sub-clusters under Cluster IV. The placement of C. indica accessions in various sub-clusters and groups in the dendrogram was based on molecular differentiation of individual accessions rather than their geographical origin. Very low genetic diversity and destruction of its natural habitat pose serious threat to C. indica even in the Citrus Gene Sanctuary in Nokrek Biosphere Reserve (NBR) in Meghalaya. Low genetic variability, heterozygosity and Shannon's information index in C. medica, C. latipes and ‘Memang athur’ are also concerns that need to be addressed for developing appropriate strategies to conserve the genetic diversity extant in these valuable genetic resources.     

Utility of RAPD,ISSR, IRAP and REMAP markers for the genetic analysis of Citrus spp.

The application and informativeness of RAPD, ISSR, IRAP and REMAP markers to study the genetic diversity and relationship among the Citrus and its relative genotypes were investigated. High levels of polymorphism were observed for all four marker systems. The RAPD technique generated the highest number of polymorphic bands and average number of polymorphic band per assay unit. Average limit of the discriminating power was very close to its actual discriminating power of each marker. The highest and the lowest values of effective number of patterns were obtained from the marker REMAP (5.94) and RAPD (4.48), respectively. Correlation between the genetic similarities matrices were estimated from all four markers using the Mantel matrix correspondence test, and results showed significant correlations among the RAPD, ISSR, IRAP and REMAP similarity matrices. The highest correlations were found comparing RAPD and ISSR markers, whereas RAPD and REMAP (r = 0.143) markers were poorly correlated. To assess the usefulness of the overall information provided by these marker data for establishing phylogenetic relationships and Citrus germplasm classification, cluster analysis was performed. All four techniques, solely or in combination, discriminated the genotypes very efficiently and generated a high similarity in dendrogram topologies, although some differences were observed. The linkage analysis was conducted based on the segregation of 38 RAPD, 13 ISSR, 19 IRAP and 9 REMAP loci in 96 progeny of an intergeneric cross Citrus sinensis and Poncirus trifoliata. Among the 81 studied loci 65 loci distributed on five linkage groups. Comparing the result obtained with RAPD, ISSR, IRAP and REMAP markers in this study, IRAP and REMAP proved to be as a reliable molecular marker for fingerprinting, mapping and diversity study of Citrus and its relatives.     

Chromosome observation method at metaphase and pro-metaphase stages in diploid and octoploid strawberries

Chromosome observation is necessary to elucidate the structure, function, organization, and evolution of octoploid strawberry plants’ genes and genomes. However, distinguishing strawberries’ chromosomes from one another using light microscopy is extremely difficult, not only because of their small size and large number, but also because current chromosome observation methods are insufficient. Chromosome preparation and staining using maceration enzymes, acetic acid, and DAPI (4′,6-diamidino-2-phenylindole) were improved for this study to obtain clear images of somatic chromosomes in Fragaria vesca (2n = 14) and Fragaria×ananassa (2n = 56). Collected root tips of octoploid plants were placed in 0.002 M 8-hydroxyquinoline solution for 1 h and stored at 4 °C for 16 h. Subsequently, they were fixed using 3:1 absolute alcohol:glacial acetic acid for 40 min, hydrolyzed in the 1N HCl solution at room temperature for 2 h, macerated using an enzyme solution for 25 min at 42 °C, and stained in 1.5% lacto-propionic orcein solution. On the other hand, in case of DAPI staining, the macerated root tips of octoploid plants were soaked in 60% acetic acid for 5 min before staining. Clear digital images of F. vesca and F.×ananassa were obtained using light and fluorescent microscopy. Their respective 14 and 56 chromosomes were counted. Fluorescent microscopy yielded clear chromosome images at the pro-metaphase in F. vesca and F.×ananassa. This chromosome observation method alleviates the difficulties that have heretofore hindered chromosome analyses of strawberry plants.     

Production protocol development for greenhouse cut Linaria, Lupinus, and Papaver flowers

Linaria maroccana Hook. f. Ann., ‘Lace Violet’, Lupinus hartwegii ssp. cruikshankii Lindl. ‘Sunrise’ and Papaver nudicaule L. ‘Meadow Pastels’ seeds were directly sown into 105 cell plug trays and received either ambient light or supplemental high intensity discharge (HID) lighting. For each species, a 2 × 3 × 3 factorial was used with two light intensities during propagation, three transplant stages, and three night temperatures. Seedlings were transplanted at the appearance of 2–3, 5–6, or 8–9 true leaves. Transplanted Linaria and Papaver seedlings were placed at 5/11, 10/16, or 15/21 ± 1 °C night/day temperatures and Lupinus seedlings were placed at 15/24, 18/25, or 20/26 ± 2 °C night/day temperatures. For this study, the optimum production temperature for Linaria was 10/16 °C as the cut stems produced at 15/21 °C were unmarketable and production time was excessively long at 5/11 °C. At 10/16 °C, Linaria seedlings should be transplanted at the 2–3 leaf stage to maximize stem number, stem length and profitability. For Lupinus the optimum temperature was 15/24 °C due to long stems and high profitability per plant. Lupinus seedlings should be transplanted at the 2–3 leaf stage when grown at 15/24 °C to obtain the longest and thickest stems; however, $/m² week was higher for plants transplanted at the 8–9 leaf stage due to less time in finishing production space. For Papaver, the 15/21 °C temperature was optimal as that temperature produced the longest stems in the shortest duration, resulting in the highest $/m² week. At 15/21 °C Papaver plants should be transplanted at the 2–3 leaf stage. Supplemental HID lighting had no effect on any of the species.     

Use of ISSR,SRAP, and RAPD markers to assess genetic diversity in Turkish melons

The genetic relationships among 63 melon (Cucumis melo L.) genotypes collected from various regions of Turkey were determined by comparing their molecular ISSR, SRAP, and RAPD markers with those of 19 foreign melon genotypes to investigate the taxonomic relationships and genetic variation of Turkish melon germplasm. Total 162 polymorphic markers (69, 18, and 75 obtained from ISSR, SRAP, and RAPD primers, respectively) were used to define the genetic similarity among the melon genotypes by dendrogram or two and three dimensional scalings. The average similarity (SM coefficient) between any two pairs of accessions examined as estimated by molecular variation was 0.73 ± 0.48. Within-group genetic similarities ranged between 0.46 and 0.96. Related genotypes or genotypes collected from similar regions were partitioned to similar clusters. Southeastern Anatolian genotypes were distinctly apart from group inodorus and group cantalupensis (sweet) genotypes. This reinforced the position of Turkey in the secondary genetic diversity center of melon. The genetic diversity among Turkish genotypes (H = 0.28 and I = 0.42) was only a little less than that of the world accessions (H = 0.30 and I = 0.45). On the other hand, the percentage of polymorphic loci among Turkish melon genotypes (90.7%) was even higher than that of the world accessions (87.6%).     

Genetic relationships among nine cultivated taxa of Calliandra Benth. (Leguminosae: Mimosoideae) using random amplified polymorphic DNA (RAPD) markers

Random amplified polymorphic DNA (RAPD) marker was used to assess genetic diversity and inter-specific relationships among nine taxa of Calliandra (Leguminosae: Mimosoideae) grown in Indian gardens. DNA from leaf sample was isolated and RAPD analysis was performed using 22 primers. The genetic similarities were analyzed from the dendrogram constructed by the RAPD data using a similarity index which supported the segregation of the nine taxa of the genus into two groups; the sect. Androcallis with seven taxa, viz. C. haematocephala, C. haematocephala var. alba, C. surinamensis, C. tweedii, C. tergemina var. emarginata and C. selloi and sect. Calliandra having two species namely, C. inermis and C. calothyrsus. The intra-generic classification and phylogeny inferred from molecular markers supported the traditional classification of the genus based on morphological characters at the level of sections and series except in case of C. selloi (C. brevipes) which did not show much genetic similarity with C. tweedii and C. surinamensis; all the three species being members of the sect. Androcallis series Androcallis.     

Eggplant relatives as sources of variation for developing new rootstocks: Effects of grafting on eggplant yield and fruit apparent quality and composition

We propose the utilization of eggplant (Solanum melongena L.) interspecific hybrids derived from crosses with closely related species as an approach for developing new improved rootstocks for eggplant. Here we investigate rootstock effects on fruit yield, apparent quality and proximate and mineral composition of S. melongena ‘Black Beauty’ (BB) scions grafted on interspecific hybrid rootstocks developed from crosses of S. melongena with Solanum incanum L. (SI × SM) and Solanum aethiopicum L. (SM × SA). The results are compared with non-grafted (BB control) and self-grafted (BB/BB) controls and with S. melongena ‘Black Beauty’ scions grafted onto Solanum torvum Sw. (STO) and Solanum macrocarpon L. (SMA) rootstocks. All treatments were grown in a soil naturally infested with root-knot nematodes (mostly Meloidogyne incognita (Kofoid and White) Chitwood). SI × SM and SM × SA interspecific hybrids had high germination (≥90%) and total graft success (100%). Contrary to what occurred with all other treatments, no plants from scions grafted onto these hybrid rootstocks died during the experiment. In particular, the SI × SM hybrid rootstock conferred the highest vigour to the scion, which resulted in the highest values for fruit earliness and early and total yield. Little difference was observed among treatments for apparent fruit quality traits, except for a greater fruit calyx length and prickliness of fruit grafted onto SMA rootstocks. A similar result was obtained for fruit composition where phenolics content was higher in fruit from plants grafted onto SMA rootstocks. Grafting eggplant onto interspecific eggplant hybrids, especially on the SI × SM hybrid, has proved advantageous for eggplant production, as the high vigour and good compatibility of the rootstock with scion results in improved early and total yield without negative effects on apparent fruit quality or composition. Interspecific hybrids represent an alternative to the commonly used STO rootstock, which is a wild species with irregular germination.     

Pollination with laser-irradiated pollens breaks cross-incompatibility between zicaitai (Brassica campestris var. purpurea) and ornamental kale (Brassica oleracea var. acephala) to produce hybrids with the aid of ovule culture

The objective of this study was to produce interspecific hybrids between an Ogura-cytoplasmic male sterile (CMS) line of zicaitai (Brassica campestris var. purupurea, 2n = 20) and cultivars of ornamental kale (Brassica oleracea var. acephala, 2n = 18) to develop a CMS system for hybrid seed production. Pollination with pollen grains of ornamental kales irradiated at a power output of 9.0 mW with a He–Ne laser for 3 min could overcome the cross-incompatibility between the species concerned. Intact hybrids could be efficiently produced from ovules cultured on Murashige and Skoog media supplemented by 0.2 mg l⁻¹ 6-benzyladenine. Chromosome number of hybrids was confirmed to be 2n = 19. Hybrids resembled ornamental kales in leaf morphology and in vernalization response. Pollens of hybrids had a sterile appearance. Moreover the hybridity of the putative hybrids was confirmed by RAPD data on a DNA fragment of 820 bp.     

Correlation of saponin content and Fusarium resistance in hybrids from different ploidy levels of Lilium Oriental

Lilium Oriental is of great commercial value, but large losses in production can result from its susceptibility to diseases caused by Fusarium ssp. Here we report a mutant of Lilium Oriental resistant to Fusarium, Cai-74, which was generated from crossing tetraploid (from ‘Star fighter’) and diploid (‘Cor. Amore’ × ‘Acapulco’) plants. Hybrid progeny were screened via inoculating Fusarium oxysporum into tissue cultured plantlets in a greenhouse. Although Cai-74 had a saponin content of 3.81 mg g⁻¹, which is much higher than its parents, the highly Fusarium-resistant wild species Lilium dauricum had the highest content of 4.11 mg g⁻¹ among the tested genotypes. Cai-74 had a 3A karyotype rather than 3B found in normal plants of Lilium Oriental. Taken together, our results suggest that Cai-74 bears a chromosomal variation in its structure, and that the saponin content in the lily scales correlate with the Fusarium resistance of Lilium Oriental. Cai-74 could be used as a gene resource for breeding Fusarium-resistant cultivars of Lilium Oriental.     

Genetic diversity and population's structure in Tunisian strawberry tree (Arbutus unedo L.)

A growing interest in the use of the Strawberry tree (Arbutus unedo L., Ericaceae) has been recently reported for industrial, pharmaceutical and chemical fields. However, the bulk material comes from natural populations because of the lack of selection of interesting cultivars. In Tunisia, A. unedo populations are severely destroyed due to deforestation and over-collecting. The species occurs in small scattered populations decreasing progressively in size. Yet, no conservation or improvement programs are attempted to preserve and promote the potential value of this resource. In this work, we assessed the genetic diversity of nine Tunisian populations of A. unedo L. from different bioclimates, using 65 polymorphic RAPD loci. The analysis of the genetic variation within and among populations is primordial to elaborate conservation and improvement programs. A low genetic diversity within a population estimated by both Nei's (He) and Shannon's diversity (H′) indices (0.155 < He < 0.248; 0.229 < H′ < 0.364) was observed due to genetic drift and selfing. At the species level, the amount of the within population variation estimated by Shannon's index (H_POP/H_SP = 0.686) and the molecular variance (80.67%) was higher than that among populations. A moderate genetic differentiation among populations (Φ_ST = 0.193 and G_ST = 0.314) which could be attributed to the long seed distance dispersal was detected. The UPGMA dendrogram based on Φ_ST values showed three clusters each including populations without relationship to bioclimatic or geographical origin indicating that differentiation occurs at a local space scale. The in situ protection measures should be made appropriately according to a population within bioclimates. The ex situ conservation and the selection of genotypes should involve extensive collection of seeds or cuttings from the within populations rather than among them.     

Production of inter-section hybrids between Primula filchnerae and P. sinensis through ovule culture

Inter-section hybrids were obtained in the reciprocal crosses between Primula filchnerae (2n = 2x = 24) of Sect. Pinnatae and P. sinensis ‘Fanfare’ (2n = 2x = 24) of Sect. Auganthus by rescuing ovules on half-strength (1/2) Murashige and Skoog's (MS) medium supplemented with 50 g l⁻¹ sucrose, 2.5 g l⁻¹ gellan gum, 0.1 mg l⁻¹ α-naphthaleneacetic acid (NAA), 0.1 mg l⁻¹ 6-benzyladenine (BA) and 50 mg l⁻¹ gibberellic acid (GA₃). In ovule culture, germination occurred with radicle elongation but no plumule was observed. The radicle kept on the initial medium showed root proliferation with callus formation. When the calluses were transferred to (1/2)MS media containing 30 g l⁻¹ sucrose and 3 g l⁻¹ gellan gum, without plant growth regulators (PGRs) or with 1 mg l⁻¹ zeatin and 0.1 mg l⁻¹ NAA, plantlets were regenerated. The plants thus obtained were confirmed to be hybrids through flow cytometry (FCM) and random amplified polymorphic DNA (RAPD) analyses. The hybrid obtained when P. filchnerae was used as the maternal parent was diploid, whereas hexaploid hybrid was obtained when using P. sinensis as the maternal parent. The hexaploid hybrid might be produced through chromosome doubling of a triploid originated from the fertilization of P. sinensis with unreduced pollen of P. filchnerae.     

Molecular characterization and analysis of somaclonal variation in chrysanthemum cultivars using RAPD markers

Molecular characterization using RAPD analysis was carried out in eight cut flowers and two pot plant cultivars of chrysanthemum. Three of them (‘Refocus’, ‘Red Reagan’, and ‘Sheena Select’) were established in vitro and the occurrence of somaclonal variation was studied using the same molecular technique. Two induction media (MS + 0.1 mg l⁻¹ NAA + 0.1 mg l⁻¹ BA, and MS + 2.0 mg l⁻¹ IAA + 0.5 mg l⁻¹ Kinetin), and two proliferation media (MS + 0.1 mg l⁻¹ NAA + 0.2 mg l⁻¹ BA, and MS + 4.0 mg l⁻¹ IAA + 2.0 mg l⁻¹ Kinetin) were employed in order to evaluate the effect of the medium composition in the shoots’ stability. Likewise, the effect of the culture age was considered in assessing genetic stability. Monthly subcultures were carried out, identifying the origin and history of the shoots, throughout a nine-month proliferation period followed by acclimatization. Molecular markers were obtained in every subculture cycle and from the acclimatized plants. Only one shoot from the 7th subculture of the cultivar ‘Refocus’ showed a different band pattern. The use of RAPD for chrysanthemum cultivar characterization and somaclonal variation detection is discussed.     

Use of ISSR markers to assess genetic diversity of African edible seeded Citrullus lanatus landraces

We used the twenty primers to evaluate the genetic variability of 80 individuals belonging to four accessions of edible seeded Citrullus lanatus originated from Côte d’Ivoire. Edible seeded C. lanatus, named “egusi” or “pistachio”, had a great importance in nutrition in West Africa. Nevertheless, due to its neglected status no study to our knowledge has been devoted to its genetic variability using DNA markers. The twenty ISSR primers generated 258 bands among which 252 were polymorphic (97.67%). On the whole, the bands generated revealed three types of profile sharply distinct from each other with minor differences within each type. One profile (P1) was most frequent with 65 individuals. Three accessions (NI084, NI127 and NI145) generated the three types of profile and had medium values of genetic diversity (GD = 0.246–0.275, respectively). On the opposite, the accession NI076 only contained individuals of the most represented type of profile (P1) and had the lowest genetic diversity (GD = 0.055 ± 0.017). The pairwise genetic distance between the 80 individuals varied from 0 to 0.61. The Factorial Component Analysis and the dendrogram clearly separated the 80 individuals into three clusters corresponding to the three types of profile. The results showed that clusters were well separated from each other whereas accessions were not. Our results suggest that high number of individuals should be taken into account for sampling missions and conservation strategies because accessions were not well differentiated from each other. Local agricultural practices consisting of frequent seeds exchanges between farmers and the conservation of harvested seeds for next year culture could be one explanation.     

DNA content,morphometric and molecular marker analyses of Citrus limonimedica, C. limon and C. medica for the determination of their variability and genetic relationships within the genus Citrus

This work investigated the fingerprinting and phenotyping of Citrus germplasm; species selected were of historical importance belonging to Citrus limonimedica Lush. and its supposed ancestors, along with some other species of the Citrus genus. An integrated approach based on the exploitation of nuclear DNA content, morphological traits and molecular markers, such as RAPD fingerprints and ITS-based SNPs, was employed. We studied a core collection of 54 distinct accessions, including 43 genotypes of the Citrus species (18 species or supposed species) and 11 genotypes of the Poncirus genus, which was used as the reference outgroup. Morphological trait analysis and statistical analysis of DNA content and markers were useful for reconstructing a Citrus phylogeny. In particular, our experiments aimed at estimating the genetic variation within and the genetic relatedness among C limon (L.) Burm., C. limonimedica and C. medica L. to shed light on the hybrid origin hypothesis of C. limonimedica. The results of the multidisciplinary analyses allowed us to confirm a remarkable differentiation between Poncirus and Citrus genera and to highlight a close relationship among the three investigated Citrus species but a distinct difference between these three species and other species in the Citrus genus. RAPD fingerprints and ITS polymorphisms enabled us to point out a variation gradient between lemon and citron, with C. limonimedica as a possible intermediate species. Some accessions of C. medica and C. limonimedica that deviate from such a trend suggest recurrent introgression and/or hybridisation with other species of Citrus.     

Interspecific variations in seed germination of Corylopsis

This study was initiated to investigate the differences in germination percentages and rates between Corylopsis coreana Uyeki and Corylopsis sinensis var. calvescens Rehder & E.H. Wilson following a warm stratification (WS) and cold stratification (CS), and to study the effect of different WS temperatures interacting with different durations of CS. Warm stratification at 10 °C, 15 °C, 20 °C, and 25 °C was given for 1 month (1 M 10 °C, 15 °C, 20 °C, and 25 °C WS) followed by 0 M, 1 M, 2 M, and 3 M of CS at 5 °C (0 M, 1 M, 2 M, 3 M CS) and seeds were germinated in an air conditioned greenhouse maintained at 18.5 °C/18 °C. On average, less than 1% of C. coreana seeds germinated when sown without any WS and CS or with 1 M 15 °C, 20 °C, and 25 °C WS without CS treatment. However, 26% C. coreana seeds germinated after 1 M 10 °C WS without any CS treatment. Germination was not affected by WS temperatures when followed by 2 M 5 °C CS. It is concluded that C. coreana exhibited low seed germination at 10 °C and that this temperature could be considered the upper limit of CS for C. coreana. Only 2 M CS was required for more than 90% seeds to germinate. However, C. sinensis var. calvescens required longer than 3 M CS for more than 29% seeds to germinate. This clearly shows that there is an interspecific variation in optimum dormancy-breaking requirements.     

Taxonomic revision of Dendrobium moniliforme complex (Orchidaceae)

Taxonomic revision of Dendrobium moniliforme complex is presented. D. moniliforme complex is characterized by the even slim stems, bracts with brownish zone, semi-spherical anther cap and the hairy disc of lip. Dendrobium tosaense, Dendrobium officinale and Dendrobium guangxiense were excluded by having membranous bracts lacking brownish zone, anther cap conical and bifid. Two species are recognized in this complex, i.e., D. moniliforme and Dendrobium wilsonii. D. wilsonii differs from D. moniliforme by having elliptic leaves about 1.3–2 cm wide, dorsal sepal 3.0–4.0 cm long, 0.6–0.9 cm wide, petals elliptic to oblong, 3.0–4.0 cm long, 1.0–1.5 cm wide, lip elliptic to ovate–lanceolate, 2.6–3 cm long, 1.2–1.5 cm wide.