Karyotype studies in South American species of Solanum subgen. Leptostemonum (Solanaceae)

Mitotic chromosome numbers and karyotypes of 13 South American species (12 native and one naturalized) from four sections of SOLANUM subgen. LEPTOSTEMONUM were studied. Chromosome numbers of S. ACERIFOLIUM, S. AENICTUM, S. CONDITUM, S. CONSIMILE, S. INCARCERATUM, and S. PLATENSE are reported for the first time. The number 2n = 24 was found in most species, while 2n = 22 was found in S. MAMMOSUM and S. PLATENSE. The latter is the second SOLANUM with this unusual number. Satellites are always present and were visible in more than 50 % of the cells studied. Karyotypes are symmetrical: M and SM chromosomes are common, whereas ST chromosomes are rare. The karyotypes of S. AENICTUM, S. MAMMOSUM, and S. PANICULATUM are comparatively asymmetrical. Species can be distinguished by a combination of chromosome number, karyotype formulae, karyotype length, the position of satellites in a particular chromosome pair, and asymmetry indices. The phenogram obtained does not reflect the sectional arrangements or the systematic affinities of the species studied. In sect. ACANTHOPHORA, increased asymmetry is associated with derived characters (strong andromonoecy, winged seeds, mammiform fruits). Diversification in the subgenus is suggested to be related to visible chromosome rearrangements and cumulative, cryptic structural changes may have also played a relevant evolutionary role.     

Karyological studies in Jaborosa (Solanaceae)

Sixteen species of Jaborosa (Solanaceae), including eight endemic to Argentina, were studied karyologically. The numbers n  = 12 and/or 2n  = 24 were found in all species, the majority of the cases being new reports. Mitotic chromosomes were small- to medium-sized, the average length varying from 2.95 to 4.93 µm. All species had one to three chromosome pairs with satellites. The karyotypes, obtained for 13 species, were slightly asymmetrical: A ₁ ranged from 0.228 to 0.483, A ₂ ranged from 0.095 to 0.182, and Paszko's asymmetry index ranged from 0.84 to 3.47. In all species, metacentric chromosomes were the most common, followed by submetacentrics, but subtelocentrics were rare. Morphological similarities and sectional arrangements were not reflected in either a principal components analysis plot or asymmetry index plot, but the species could be singled out by their karyotype formulae and the different karyotype parameters taken. In Jaborosa , a notably diversified genus, exo-morphological evolution has taken place, together with evident chromosome rearrangements, whose disposition is different and not as clear as in related genera.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 467–478.     

Karyotype analyses in three Patagonian and S. Andean endemic genera ofNicotianeae (Solanaceae)

The somatic chromosomes and karyotypes of threeNicotianeae have been studied for the first time. All of them have 2n = 2x = 22 and symmetrical karyotypes.Benthamiella pycnophylloides has 9 m pairs + 1 sm pair + 1 st pair; pairs 2, 4, 5, and 11 bear microsatellites.Combera paradoxa andPantacantha ameghinoi have 9 m pairs + 2 sm pairs; pair 11 ofC. paradoxa is satellited, while pair 9 ofP. ameghinoi bears microsatellites and shows a pericentric inversion in heterozygous state in 20% of the seedlings. Results are compared with previous chromosome reports for the tribe. The cytological data support their present position in the family system. Besides,Benthamiella, Combera andPantacantha appear to be primitive genera ofNicotianeae, a comparatively advanced tribe within the family.Chromosome studies onNicotianeae (Solanaceae) 1.     

Karyotypic studies in Solanum section Lasiocarpa (Solanaceae)

Mitotic chromosomes of 13 species included in Solanum sect. Lasiocarpa were studied. All species have 2n = 24. The chromosome numbers of S. stagnale, S. felinum, and S. repandum are reported for the first time. Statistical analyses of chromosomes, genome length, and centromere position yielded estimates of karyotype composition and asymmetry. A generalized karyotype of the section shows that most of the chromosomes are metacentric (73%) or submetacentric (25.6%). Two pairs of subtelocentric chromosomes are present only in S. sessiliflorum. Satellites are quite common, characterizing chromosomes for ten species and are attached to the short arms of either m or sm chromosomes. They could be seen in 10% to 70% of the cells. Only S. pseudolulo bears two satellited chromosomes, one of them attached to a long chromosome arm. Although the section is chromosomally quite homogeneous, species can be distinguished by karyotype formula, presence of satellites in a particular chromosome pair, and total chromosome length. There are no indications of major chromosomal rearrangements within the section. Using cytological data exclusively, cluster analysis indicates S. sessiliflorum is isolated in the section. Solanum candidum and S. vestissimum are somewhat isolated as well and have unique karyological traits. Solanum pectinatum has a peculiar karyotype, but in the phenogram it is not particularly separated. Karyotype features suggest that morphological differentiation was not always followed by chromosomal divergence. The origin of the domesticated S. quitoense is no further elucidated by our data.     

Karyotype differentiation of four Cestrum species (Solanaceae) revealed by fluorescent chromosome banding and FISH

The karyotypes of four South American species of Cestrum (C. capsulare,C. corymbosum,C. laevigatum and C. megalophylum) were studied using conventional staining, C-CMA/DAPI chromosome banding and FISH with 45S and 5S rDNA probes. The karyotypes showed a chromosome number of 2n = 2x = 16, with metacentric chromosomes, except for the eighth submeta- to acrocentric pair. Several types of heterochromatin were detected, which varied in size, number, distribution and base composition. The C-CMA(+) bands and 45S rDNA were located predominantly in terminal regions. The C-CMA (+) /DAPI (+) bands appeared in interstitial and terminal regions, and the C-DAPI (+) bands were found in all chromosome regions. The 5S rDNA sites were observed on the long arm of pair 8 in all species except C. capsulare, where they were found in the paracentromeric region of the long arm of pair 4. The differences in band patterns among the species studied here, along with data from other nine species reported in the literature, suggest that the bands are dispersed in an equilocal and non-equilocal manner and that structural rearrangements can be responsible for internal karyotype diversification. However, it is important to point out that the structural changes involving repetitive segments did not culminate in substantial changes in the general karyotype structure concerning chromosome size and morphology.     

Karyotype studies of some species of Dalechampia Plum. (Euphorbiaceae)

Karyotype studies in eight species of Dalechampia , including 10 natural populations, revealed chromosome numbers (2 n = 36, 46, 138 and 198) differing from two numbers cited in the literature (2 n = 44 and 72). The basic number x = 6, as in the genus Acalypha , may be considered ancestral in Dalechampia. Analysis of chromosome number, haploid chromosome length and karyotype symmetry suggests that the major chromosome mechanism acting in karyotype evolution of Dalechampia is polyploidy, but differences in chromosome morphology may be caused by chromosome rearrangements.     

Karyotype and meiosis studies in three South African Pyrgomorpha species (Orthoptera: Pyrgomorphidae)

Two South African Pyrgomorpha species have reduced chromosome numbers, due to centric fusions between the largest autosomes and the medium and small autosomes. P. rugosa has 2n=11(XO) (4 pairs of submetacentric and 1 pair of acrocentric autosomes) and P. granulata has 2n=13(XO) (3 pairs of submetacentric and 3 pairs of acrocentric autosomes). A third South African species has a typical Pyrgomorphidae number of 2n=19(XO) (acrocentrics). The mean chiasma frequency of the 2n=19 species is higher than that of the other two, although the frequencies of distal chiasmata in all three are similar. The recombination potential of the two species with lower chromosome numbers has been reduced, due to fewer crossovers in comparison to the 2n=19 species, as well as to independent assortment.     

Floral mechanisms in the tribeSalpiglossidae (Solanaceae)

SinceDelpino (1869),Juel (1894, 1911), andMüller (inMöller 1921: 164), the flowers ofSolanaceae have received little attention with regard to function and pollination syndromes. The present paper deals with representatives of 6 of the 9 known salpiglossidean genera. Previous observations are updated and discussed at the tribal level. Most species studied are butterfly- or moth-pollinated. With the exception ofSalpiglossis, the fertile floral parts are concealed in the corolla tube, and their arrangement is specially suited for deposit of the pollen on the lepidopteran tongue. Particularly notable are (a) abundant stigmatic secretion that makes the pollen sticky, and (b) versatile anthers that optimize contact between the tongue and the thecae.Brunfelsia andBrowallia exhibit a mechanism analogous to that ofApocynaceae, however, with two entrances instead of five. When the tongue is inserted, it is forced to contact the stigma and becomes glued with its secretion. When the tongue is pulled out, it touches the anthers and causes slight balancing movement. InStreptosolen, very probably an ornithophilous descendant of theBrowallia stock, the mechanism is much simplified.Leptoglossis andHunzikeria bear a novel device for pollen deposition: there are two fertile wheel-like anthers that are capable of full rotation up to eight turns.     

Graft formation in Solanum pennellii (Solanaceae)

Three phases of cohesion were observable during the development of compatible autografts in Solanum pennellii. Phase I cohesion 1) lasted 4–5 d after grafting, 2) was characterized by an average increase in tensile strength of 4 g breaking weight (BW) mm^–2 graft area (GA) d^–1, and 3) correlated positively with cellular interdigitation at the graft interface. The fresh weight of the scion increased by approximately 5% d^–1 during the first 2 d after grafting. Phase II cohesion occurred 5–15 d after grafting, during which time 1) the tensile strength of the graft union increased by 14 g BW mm^–2 GA d^–1, 2) vascular differentiation across the graft interface was completed, and 3) the fresh weight of the scion increased by 9% d^–1. Phase III cohesion occurred subsequent to 15 d after grafting, during which time 1) the tensile strength of the graft union leveled off at a value similar to that of an ungrafted internode, and 2) the fresh weight of the scion increased by 14% d^–1. These results are discussed relative to mechanisms underlying the formation of compatible grafts.     

Hair morphology and systematics ofPhysalis (Solanaceae)

Hair morphology was exammed on developing seedlings and mature plants of ten species from five of seven series inPhysalis. The taxonomic importance of hair development and the distribution of hair types then was evaluated with respect to other comparative data. Two classes of hair types were observed, as found in earlier investigations ofSolanum andRhododendron. The first hair class comprises a sequence from unbranched hairs to dendroid-stelliform hairs. Hairs of this class show considerable variability among taxa in size, presence or absence of glandular tips, and presence and degree of branching, and so were useful in making taxonomic comparisons. The second hair class consists of short hairs, each tipped with a multicellular gland. This second hair class was not useful taxonomically because of its lack of variability in morphology and its often rare occurrence on a plant. The taxa studied exhibit distinctive trichome features which serve to distinguish series and, in some cases together with other data, provided new insight into previously enigmatic species relationships.     

Notes on Withania (Solanaceae) in Somalia

The identity of Withania reichenbachii is established, the name is neotypified, and the species is described and illustrated. The new combination W. grisea (Hepper & Boulos) Thulin is made. The typification of W. somnifera is discussed, and it is concluded that the present typification can stand. A key to and a synopsis of the four species of Withania now recognised in Somalia are given.     

Pollen Heteromorphism in Nicotiana tabacum (Solanaceae)

Pollen heteromorphism is defined as the production by a single plant of different fertile pollen types in all its anthers, and thus all flowers, throughout its life cycle. Eight cultivars of Nicotiana tabacum, as well as its ancestors (N. tabacum is an amphiploid hybrid 4 × from a cross between N. sylvestris and N. tomentosiformis) and recent hybrids were analyzed. Most cultivars and the hybrids are heteromorphic (producing 3- and 4-aperturate pollen grains), whereas both parent species are homomorphic (3-aperturate). Heteromorphism is a common consequence of polyploidization and these results agree with this interpretation. There is a significant variation in the proportions of the two pollen types among cultivars (genetic component), but also (with a much lower component of variance) within each cultivar, between plants (genets), flowers of a plant, and even anthers of a flower. This is interpreted as a release of the selective pressure: the cultivars of N. tabacum were obtained after several generations of selfing and are themselves selfers. Selfing, by removing pollen mixtures on a stigma, removes pollen competition, which is the drive for heteromorphism, and allows for a large variation of the proportions of the different pollen types.     

Alkaloids of Solanaceae (nightshade plants)

Alkaloids are nitrogen containing compounds found in many plants. They are products of plants secondary metabolism derived from amino acids, purines, pyrimidines or terpene. Most of them are drugs. The biological activity of some alkaloids has led to their intensive exploitation by humans, as pharmaceuticals, narcotics or poisons. During the past 30 years, major technical advances have led to substantial progress in our understanding of alkaloid biochemistry, but since then biosynthetic pathways of some alkaloids are not explained. The nightshade (Solanaceae) are widespread family of plants containing tropane alkaloids or glycoalkaloids. Both of them are naturally produced, as a defense mechanism against insects, predator and disease. On the other hand, most of the species of Solanaceae family have been used by human since several centuries.     

Giemsa C-banded karyotypes inCapsicum (Solanaceae)

Giemsa C-banding is applied for the first time inCapsicum, allowing preliminary karyotype differentiation of six diploid species. Comparison of interphase nuclei and heterochromatic C-bands reveals striking differences between taxa and contributes to their taxonomic grouping. Therefore, C-banding appears to be a powerful tool for the cytogenetics and karyosystematics of the genus. Banding patterns are characterized by the omnipresence of centromeric bands and a variable number of smaller to larger distal bands, with the addition of intercalary bands in some cases. Satellites are always C-positive. Relationships between species and possible trends of karyotype evolution are discussed, with special reference to the origin of x = 13 from x = 12 and the increase of heterochromatin, regarded as advanced features.Chromosome studies inCapsicum (Solanaceae), III. For the first and the second part seeMoscone (1990, 1993).     

Ethnobotany of the genusCyphomandra (Solanaceae)

Plants of the genusCyphomandra (Solanaceae) have long been utilized for their edible fruits in their native Latin America. The best-known species is the domesticated tree tomato or tamarillo,Cyphomandra betacea. This species, popular as a raw or cooked fruit, is widely cultivated in Andean South America and is now dispersed worldwide in subtropical areas. Its origin and wild relatives are still unknown, but there are tentative reports of wild populations ofC. betacea in southern Bolivia and northwestern Argentina. Wild species ofCyphomandra such asC. hartwegii, C. sibundoyensis, andC. cajanumensis also produce edible fruits. Other species ofCyphomandra are used in medicinal preparations and as dyes. This group of plants is of increasing economic importance and may have considerable potential for future exploitation.     

Cladistic relationships in the genus Schizanthus (Solanaceae)

The cladistic relationships between Schizanthus species, based primarily on morphology, and chemical characters when available are presented. In this investigation we did not find supporting evidence for the theories grouping of Grau and Gronbach (Mitt. Bot. München 20 (1984) 111). The anomalous presence of hygrolines in S. integrifolius Phil. is a case of primitivism and isolation of this group, and it is not closely related to S. grahamii Gill. or S. hookeri Gill. Pseudohygrolines in S. pinnatus R. et P., S. hookeri, and S. litoralis Phil. appear as ancestral features and are unreliable for establishing phylogenetic relationships. The chemical evolution in Schizanthus runs, in parallel from the pyrrolidine to the tropane series, with subsequent dimerization or trimerization.     

Dioecy in South American Deprea (Solanaceae)1

Dioecy in the Solanaceae is rare, occurring in < 1 percent of the species worldwide and known in only two species from South America. We report the occurrence of cryptic dioecy in the Neotropical genus Deprea. Studying herbarium material of the Venezuelan endemic D. paneroi revealed morphological distinctions that tentatively served to divide collections into male and female morphs. This discovery prompted investigation of population structure, crossing studies, and morphometric analyses of 95 individuals from the largest known wild population and a small sample of greenhouse‐grown plants. About 60 percent of the population was reproductive, and of these, nearly equal numbers exhibited female or male characteristics. Plants that bore fruit and small sterile anthers were characterized as female; those that lacked fruit but produced pollen in large anthers were characterized as male. The morphology, receptivity, and developmental phenology of pistils were identical in both forms. Crossing studies revealed significant enlargement of the ovaries in open‐pollinated female flowers and female X male hand‐pollinations. The ovaries in open‐pollinated male flowers and male X male hand‐pollinations never enlarged. These results suggest that the only legitimate combination is female X male. Dioecy in the family and possible mechanisms for the evolution and maintenance of dioecy in D. paneroi are discussed.