Interspecific Combinations Research Articles

Meiosis in interspecific Hoerdeum hybrids: III Tetraploid (2x × 6x) hybrids

Meiotic pairing in 17 new tetraploid, 2x × 6x, interspecific combinations is described. Together with earlier data it is evident that the diploid I genomes of Hordeum vulgare and H. bulbosum are not homologous to the genomes of the hexaploid species. H. brevisubulatum is a true autoploid, whereas the other hexaploids are alloploids or segmental alloploids. The H genome, present in most Hordeum diploids, is homo- or homoeologous to one of the genomes in all the hexaploids except H. murinum. The H genome of the American diploids is similar to that found in the American hexaploids in contrast to the apparently diverged H genome observed in the diploid European diploid species. The hexaploid H. murinum does not seem to have a genome homoeologous to any of the diploid species studied.

Pheromones in the life of insects

Life in insect societies asks for a permanent flow of information, often carried by rather simple organic molecules. Some originate from plants as odours of blossoms or exudates from trees. Especially important are the intra- and interspecific combinations of compounds produced by the insects themselves. These are called pheromones or ecto-hormones and serve a variety of tasks. The paper deals mainly with honeybee pheromones, but takes also into consideration those of wasps and hornets. Effects of pheromones are monitored ethologically by direct observation and filming as well as in a more quantitative manner with using direct and indirect calorimetry. In all experimental set-ups alarm pheromones were used as controls. They show an up to fourfold increase of activity after a few seconds, determined for small groups of insects as well as for a whole hornet nest placed in a 25-l calorimeter. A variety of cosmetics like soaps, shampoos, lotions and perfumes are included in the investigations because of repeated reports about unwarranted insect attacks which are said to be provoked by such products. None of the applied substances provoked a significant reaction of the bees (p > 0.05). A short appendix discusses the still questionable existence of pheromones in man, which were confirmed under laboratory conditions, but not yet for daily life.

Identification of barriers to interspecific crosses in the genus Trifolium

A study of pre- and post-fertilisation barriers after interspecific crosses of diploid and tetraploid Trifolium pratense L. and wild species T. alpestre L., T. medium L. and T. sarosiense Hazsl. was aimed at finding of a promising cross combination for obtaining hybrids. The growth of pollen tubes was arrested in interspecific crosses mainly when T. pratense was at a diploid level. To investigate the post-fertilisation barriers in detail, the hybrid embryo viability was traced by two clearing treatments of immature seeds: (1) using chloral hydrate (which proved to be most appropriate); and (2) a mixture of benzyl benzoate and dibutly phthalate. In interspecific combinations T. pratense (4×) × either T. alpestre or T. sarosiense, enlargement of immature seeds occurred, but no hybrid embryo was traced. Of the wild species used as a male parent for crosses, T. medium was the only exception from the point of view of fertilisation. Globular, heart and the early torpedo stages of hybrid embryos were observed 7 days after pollination (DAP) but only when T. pratense was at a tetraploid level. When T. pratense (2×, 4×) was used as a male parent for interspecific crosses with T. alpestre, T. medium and T. sarosiense, strong defects in various stages of embryogenesis were observed, particularly wrinkled and narrowing embryo sacs caused by an expansion of endothelial cells. We conclude with the following finding: (1) to make crosses only in one direction with T. pratense as a female parent and T. medium as a male; (2) to use tetraploid plants of T. pratense; (3) and to excise hybrid embryos at an early torpedo stage, about 7 DAP.

Spatial Associations, Size–Distance Relationships and Population Structure of Two Dominant Life Forms in a Semiarid Enclave of the Venezuelan Andes

The role of three thorny legume species as nurse plants and competitive relationships with columnar cacti were evaluated in a semiarid enclave of the Venezuelan Andes. Abundance and size of three columnar cacti species (Stenocereus griseus, Cereus repandus and Pilosocereus tillianus) under isolated shrubs of three thorny legumes species (Prosopis juliflora, Acacia farnesiana and A. macracantha) were recorded and compared with open areas. Using size–distance data we inferred the intensity of intra- and interspecific competition between both life forms in a “cardonal” (xeric zone) and “espinar” (mesic zone) of the enclave. Sixty-one columnar cacti were found beneath the three thorny legume species (92%), while only 5 cactus individuals were found in open areas (8%). Comparison of observed and expected number of cactus individuals shows that S. griseus and C. repandus are significantly associated with isolated shrubs of A. farnesiana and A. macracantha. Although P. juliflora contributed more than 40% of the total legume plant cover, the number of columnar cacti under its isolated shrubs was significantly lower than would be expected by chance. In all, 19 of 21 possible plant–plant combinations between and within columnar cacti and legume shrubs were recorded (espinar: 18, cardonal: 13, common combinations: 12). In both zones, intra- and interspecific combinations among columnar cacti species were relatively high (positive correlation between the sum of neighbour plant sizes and the distances separating them). Our results strongly suggest, at least for case of S. griseus and C. repandus, that these columnar cacti species require nurse plants for their establishment. The results on interference need still support from further research. We discuss the effects of plant–plant positive interactions on natural regeneration of these columnar cacti.

Artificial Hybridizations in Five Species of Chilean Nolana (Solanaceae)

Reciprocal crosses, both intraspecific and interspecific, were made among five Chilean species of Nolana (Solanaceae), a genus native to western South America. With the exception of N. paradoxa, plants of all species used were grown from mericarps collected from wild populations. Self-pollinations were generally not successful, suggesting obligate allogamy. A total of 333 hybridizations were performed, of which 109 were intraspecific and 224 interspecific. Successful intraspecific hybridizations, as measured by formation of fruits, were produced for N. acuminata (83%), N. elegans (94%), N. paradoxa (82%), and N. rupicola (100%), however viable hybrids were only obtained for N. paradoxa. Interspecific combinations resulted in over 80% fruit set, however, viable hybrid success ranged from only 1% to 5%. Crosses included N. elegans × N. paradoxa with 20 viable hybrids, N. paradoxa × N. elegans with two hybrids, N. paradoxa × N. rupicola with seven hybrids, and N. rupicola × N. paradoxa with five hybrids. Exceptions included crosses involving N. aplocaryoides, with up to 20% fruit set. Also, the combination N. paradoxa × N. aplocaryoides with five hybrids, had a 26% success. All interspecific hybrids obtained had N. paradoxa as one of the parents, which could be related to artificial selection for high germination frequency.

2004 SIVB Congress Symposium Proceedings “Thinking Outside the Cell”: Applications of Somatic Hybridization and Cybridization in Crop Improvement, with Citrus as a Model

Although somatic hybridization techniques are being ignored by variety improvement programs for most commodities, their contribution to citrus variety improvement continnes to expland and with increasing complexity. Citrus is, one of the few commodities where somatic hybridization is reaching its predicted potential, as somatic hybrids are now possible from most desirable parental combinations. Somatic hybrid citrus plants have been produced from more than 250 parental combinations, including more than 130 at the CREC. The CREC hybrids include 34 from sexually compatible intergeneric combinations, 16 from sexually incompatible combinations, and 81 interspecific combinations. The objective of this report is to demonstrate the impact of somatic hybridization on citrus improvement programs, and to discuss its potential with other commodities. For citrus scion improvement, several applications are aimed at the development of improved seedless fresh fruit varieties, and these include symmetric somatic hybridization, haploid+diploid fusion, targeted cybridization to transfer cytoplasmic male sterility (mtCMS) from Satsuma mandarin, and triploidy via interploid crosses using somatic hybrid allotetrapoid breeding parents. For rootstock improvement symmetric somatic hybridization provides an opportunity to hybridize complementary rootstocks without breaking up successful gene combinations. Rootstock somatic hybridization is providing opportunities for improving disease and inseet resistance, soil adaptation, and tree size control. Wide somatic hybridization provides an opportunity for gene transfer from related species, including some that are sexually incompatible. Extensive field research on citrus somatic hybrid rootstocks combined with emerging molecular analyses of citrus has allowed for the development of additional strategies for rootstock improvement. These include rootstock breeding and selection, at the tetraploid level using somatic hybrid parents, and the resynthesis of important rootstocks at the tetraploid level via fusion of selected superior parents. Ongoing examples of each strategy will be provided, along with ideas for extending the technology to other commodities.

Growth and competition between seedlings of an invasive plantation tree, Acacia mangium, and those of a native Borneo heath‐forest species, Melastoma beccarianum

AbstractAn introduced plantation tree species, Acacia mangium Willd., is becoming invasive in the Brunei region of Borneo. To examine its invasive potential, a greenhouse, additive series experiment (target–neighbour) involving seedlings of A. mangium and those of a common native heath‐forest (kerangas), Melastoma beccarianum Cogn. was carried out under low and high light regimes in intra‐ and interspecific combinations over a 6‐month period. Significant variations in growth parameters (other than biomass allocation patterns) existed amongst seedlings from different treatments. A major part of this variation in growth could be attributed to the main factors of target species, neighbour species, and competition (seedling density). For the growth variables examined, the target–species response was not consistent across light regimes. Under high light conditions, Acacia was the better competitor; the Lotka‐Volterra competition coefficient effect of Melastoma on Acacia was lower (α=0.30) than the effect of Acacia on Melastoma (β=0.54). However, the reverse occurred under low light conditions with Melastoma gaining the upper hand (α=1.45 and β=0.44). These results show that light (and hence disturbance) can strongly influence the pattern and intensity of both intra‐ and interspecific competition between invasive and local flora species. Relatively intact forest is unlikely to be invaded by Acacia trees (as they are poor competitors under this scenario). On the other hand, the Acacia trees can easily invade disturbed forests, especially those prone to recurring drought and fire, and over time convert the habitats to nearly monospecific stands, as is presently being observed in Brunei.

Toward Introgression of Ornamental Cucurbita Germplasm: Generation of C. maxima ×pepo hybrids

Cucurbita maxima and C. pepo are difficult to hybridize, and it was our objective to generate F1 hybrids between ornamental cultivars of the two species. C. maxima `Lakota' and C. pepo `Jack O'Lantern'; and `OZ'; were selected as parents. `Lakota' (L) is an heirloom, hubbard-type cultivar producing pear-shaped, red-orange fruit with dark green mottling, `Jack O'Lantern'; (J) is an open-pollinated Halloween-type pumpkin cultivar and `OZ' is a Halloween-type hybrid. Sixteen plants of each cultivar were greenhouse-grown in a CRB design during the period July-Sept. 2003. Interspecific crosses were made in both directions, with intraspecific crosses (J × O) and selfs (L) serving as controls. Fruits were harvested about 20 d after pollination. Embryos were excised under aseptic conditions and grown on either full strength Murashige and Skoog (MS) media with 6% sucrose (S6), full strength MS media with 6% maltose (M6), or half strength MS media with 3% sucrose (S3). Fruit set was generally greater in the intraspecific crosses (33%) and selfs (67%) than in the interspecific crosses (15 %), with the notable exception of the interspecific combination L × J (85% fruit set). Embryos of interspecific and control crosses were about 1.5mm and >1cm long, respectively. Hypocotyl and root growth 10 d after plating was better on S3 (3.2 and 1.7 cm) than on S6 (1.6 and 0.25 cm) or M6 (0.35 and 0 cm), and a greater number of functional hybrids were obtained from embryos grown on S3 (6 plants) than on S6 (2 plants) or M6 (2 plants). The interspecific plants were backcrossed to one of the parents and novel combinations of shape, color and variegation in hybrid fruit were observed.

SELECTION AND DISPERSAL IN A MULTISPECIES OAK HYBRID ZONE

The four western North American red oak species (Quercus wislizeni, Q. parvula, Q. agrifolia, and Q. kelloggii) are known to produce hybrid products in all interspecific combinations. However, it is unknown whether hybrids are transitory resulting from interspecific gene flow or whether they are maintained through extrinsic selection. Here, we examine cryptic hybrid structure in Q. wislizeni through a broad region including contact and isolation from three other western North American red oaks using amplified fragment length polymorphism molecular markers. All four species were simultaneously detected in the genetic background of individuals morphologically assigned to Q. wislizeni, although the contribution of Q. kelloggii was minor. In some cases, introgression was detected well outside the region of sympatry with one of the parental species. Molecular structure at the individual level indicated this was due to long-distance pollen dispersal and not to local extinction of parental species. Species admixture proportions were correlated with climatic variables and greater proportions of Q. agrifolia and Q. parvula were present in the genetic background of Q. wislizeni in sites with cooler and more humid summers, corresponding with habitat preferences of the parental species. Partial Mantel tests indicated that climate was more important than distance from pollen source in this association. Despite high levels of introgression, species integrity was maintained in some populations in close proximity to the other species, providing further support to environmental selection in determining population genetic structure. Thus, the contribution of species mixtures to population genetic structure varies across the landscape according to availability of pollen, but more importantly to varying environmental selection pressures that produce a complex pattern of hybrid and pure gene pools.

SELECTION AND DISPERSAL IN A MULTISPECIES OAK HYBRID ZONE

The four western North American red oak species (Quercus wislizeni, Q. parvula, Q. agrifolia, and Q. kelloggii) are known to produce hybrid products in all interspecific combinations. However, it is unknown whether hybrids are transitory resulting from interspecific gene flow or whether they are maintained through extrinsic selection. Here, we examine cryptic hybrid structure in Q. wislizeni through a broad region including contact and isolation from three other western North American red oaks using amplified fragment length polymorphism molecular markers. All four species were simultaneously detected in the genetic background of individuals morphologically assigned to Q. wislizeni, although the contribution of Q. kelloggii was minor. In some cases, introgression was detected well outside the region of sympatry with one of the parental species. Molecular structure at the individual level indicated this was due to long-distance pollen dispersal and not to local extinction of parental species. Species admixture proportions were correlated with climatic variables and greater proportions of Q. agrifolia and Q. parvula were present in the genetic background of Q. wislizeni in sites with cooler and more humid summers, corresponding with habitat preferences of the parental species. Partial Mantel tests indicated that climate was more important than distance from pollen source in this association. Despite high levels of introgression, species integrity was maintained in some populations in close proximity to the other species, providing further support to environmental selection in determining population genetic structure. Thus, the contribution of species mixtures to population genetic structure varies across the landscape according to availability of pollen, but more importantly to varying environmental selection pressures that produce a complex pattern of hybrid and pure gene pools.

Interspecific Crosses of Lily by in Vitro Pollinated Ovules

Abstract. Because of pre-and post-fertilization barriers, successful interspecific crosses have not been reported for Liliurn using Asiatic hybrid as the mother to cross with Oriental or Lilium longiflorum. Using an in vitro ovular pollination method, where pollen tubes directly penetrate isolated ovules, this study demonstrated that 1) the Brewbaker and Kwack agar plate containing sucrose (10%), with the isolated ovules being placed ca. 1mm apart from the pollen, is optimal for pollination, 2) interspecific crossing barriers do not occur during penetration of the pollen tubes into the micropyle. 3 micropylar penetration can be obtained in all kinds of intra- and inter-specific cross combinations of lily cultivars, 4) multiple penetration occurs, in which the penetrating pollen tubes pass the embryo sac without entering the synergid cells, 5) a small amount of pollen tube penetrates the synergid cells in the A x 0 cross, and 6) completion of pollen tube penetration (8-12 h after germination) is much earlier than the division of the generative cell in sperm cells (17 h after germination), which may be the primary cause for the failure in fertilization.

Reproductive isolation in Caenorhabditis: terminal phenotypes of hybrid embryos.

Several interspecific combinations of the "elegans" group of Caenorhabditis species are cross-fertile. Most F1 hybrids from these crosses arrest during embryogenesis. Developmental defects observed in hybrid embryos include defects in gastrulation initiation, defects in embryonic compaction, and defects in embryonic elongation. These reproductive barriers have arisen multiple times in the evolution of Caenorhabditis.

Ｌｙｃｏｒｉｓの種間交雑における柱頭へのＮＡＡ処理が着果と種子形成に及ぼす影響

Lycoris albiflora, L. aurea, L. radiata and L. sanguinea were cross-bred to yield 8 interspecific combinations. When the scapes were cut at their base after crossing and kept in water, a few interspecific hybrids from 7 combinations were obtained. The percentages of fruit set and the number of seeds per capsule were increased by applying 2% Naphthaleneacetic Acid (NAA) on the stigma after pollination in three interspecific hybrids of Lycoris. Thus, the hormone treatment improved the efficiency of obtaining interspecific hybrids with Lycoris.

Chemical communication and mate attraction in echinostomes

Mate attraction is widespread among animals and appears to facilitate mating and to prevent hybridisation between closely related species. In this study we investigated mate preference between two geographical isolates of Echinostoma caproni (Trematoda, Platyhelminth) and another species of the genus Echinostoma E. sp. Because previous experiments showed a partial reproductive isolation between echinostome isolates, we examined the possibility that such isolation resulted from differential mate attraction. We compared intra-isolate, inter-isolate and interspecific pairings using two in vitro experimental designs. In the first experiment we compared mate attraction of two individuals belonging to or not belonging to the same isolate, while in the second experiment we examined mate choice when individuals were in the presence of individuals from both the same isolate and from a different isolate or a different species. Distances between worms were measured over a period of 90min. Results from both experiments suggested that mate attraction was similar for intra-isolate, inter-isolate or interspecific combinations. This lack of mate preference in vitro would therefore support an alternative hypothesis of a reproductive isolation through sperm selection.

Grafting Hensen's node.

Soon after Spemann and Mangold’s () famous demonstration in 1924 that the dorsal lip of the blastopore of the gastrulating amphibian embryo has the unique ability to induce a second axis when grafted into an ectopic site in a host embryo, Waddington (,) showed that Hensen’s node is its equivalent in amniotes. After transplanting this region into an ectopic site in interspecific combinations of rabbit, duck, and chick embryos, he found that a second axis developed, where the nervous system was derived from the host ectoderm (). Hensen’s node is situated at the anterior (cranial) tip of the primitive streak during gastrulation, and in chick embryos appears as a bulbous thickening, some 100 μm in diameter, centered around a depression, the primitive pit. At this point, the three germ layers of the embryo are in very close apposition.

Efficient selection of potato heterokaryons by flow cytometric sorting and the regeneration of hybrid plants

A method for the selection of potato heterokaryons after the electrofusion of dihaploid lines of potato (Solanum tuberosum L.) or dihaploid potato lines and Solanum commersonii has been developed. The selection of heterokaryons was based on the staining of mesophyll protoplasts with fluorescein diacetate or scopoletin. In several experiments, up to 100 000 objects were sorted in a dual laser equipped FACStar Plus, using a 160 μm nozzle and culture medium as sheath fluid. A large number of plants was regenerated from 1 intraspecific and 5 interspecific fusion combinations. RAPD analysis of 244 tetraploid plants from 5 different fusion combinations showed that 240 of these were hybrids. The potential of this selection method for the efficient integration of protoplast fusion technology into potato breeding is discussed.

Taxonomic status of Oryza glumaepatula Steud. II. Hybridization between New World diploids and AA genome species from Asia and Australia

Intraspecific and interspecific crosses were made using O. glumaepatula Steud., O. rufipogon Griff., O. nivara Sharma et Shastry, O. meridionalis Ng, and other diploid accessions from the New World to determine biosystematic relationships among the New World, Asian, and Australian AA genome species. All intraspecific and interspecific combinations produced seeds and hybrids, but at different levels of success. The O. glumaepatula, O. rufipogon, and O. nivara intraspecific hybrids were generally fertile with mean pollen stainability ranging from 75.2% to 80.1% and mean spikelet fertility varying from 32.1% to 87.7%. The O. meridionalis intraspecific crosses showed 3.8% pollen stainability and 0.1% spikelet fertility. Interspecific hybrids showed varying fertilities. Crosses of O. glumaepatula with the New World diploid accessions IRGC 103812 and 105561 produced highly fertile hybrids with 68.0% to 89.7% pollen stainability and 70.8% to 86.6% spikelet fertility. In crosses between O. glumaepatula and the Asian species and other diploid New World accessions IRGC 100961, 103810, and 104386, sterile hybrids were produced with pollen fertility ranging from 0 to 35.1% and spikelet fertility from 0 to 8.2%. IRGC 103810 and 104386 formed fertile hybrids when crossed to O. nivara and O. rufipogon, which were also interfertile. Interspecific crosses of O. meridionalis with the other species produced highly sterile hybrids.

Mitochondrial DNA sequence divergence in weevils of the Pissodes strobi species complex (Coleoptera:Curculionidae).

Mitochondrial DNA sequence divergence is unusually high between several species of the Pissodes strobi complex, in contrast to low allozyme and morphological divergences, and the ability to hybridize in the laboratory. We sequenced an 810 bp segment in seven individuals, representing four species in the P. strobi complex and one outgroup species, P. affinis Randall. The 810 bp segment covered the 3' half of the cytochrome oxidase subunit I (COI) gene. We also sequenced one specimen of P. strobi (Peck) over a 2301 bp region of mtDNA, extending from the 5' end of COI to the 3' end of COII. Uncorrected sequence divergences were below 1.1% among three specimens of P. schwarzi Hopkins, and between P. terminalis Hopping and P. nemorensis Germar. All other interspecific combinations in the P. strobi complex showed divergences of 6.0-7.5%. The outgroup species, P. affinis, had an average divergence of 12.8% from members of the P. strobi group. As in most other insects, A + T content in Pissodes mtDNA was high; transition:transversion ratio was high among lineages exhibiting low divergences, but declined with increasing sequence divergence; and inferred amino acid sequence divergences were low. The degree of sequence divergence differs markedly across different functional regions of the COI gene. The high mtDNA divergences within the P. strobi complex calculated from direct sequencing support earlier reports based on restriction site surveys; however, cladograms based on mtDNA sequence differ from those based on earlier work.

Analysis of mitochondrial genomes amongCitrus plants produced by the interspecific somatic fusion of ?Seminole? tangelo with rough lemon

Interspecific somatic fusion was performed between 'Seminole' tangelo (Citrus reticulata Blanco xC. paradisi Macf.) protoplasts isolated from embryogenic callus and rough lemon (C. jambhiri Lush.) mesophyll protoplasts. Eight plants out of ten randomly selected regenerants had 18 chromosomes and the same nuclear rDNA fragment patterns as that of the mesophyll parent. The remaining two plants showed rDNA fragment patterns from both parents and had 36 chromosomes. For the analysis of mitochondrial DNA (mtDNA),rrn26 derived from pea was used to probeBamHI digests of the regenerants. All plants showed mtDNA band patterns identical to that of the callus parent, suggesting that eight plants were cybrids and the remaining two plants were somatic hybrids. In addition to the callus parent band patterns, additional fragments from the mesophyll parent and/or a novel band fragment were revealed in some of the putative cybrids by peaatpA probe after digestion withDraI andPstI. These results suggest the occurrence of mtDNA recombination/rearrangement inCitrus cybrids produced by somatic fusion in this interspecific combination.

Hybridization of AA genome rice species from Asia and Australia I. Crosses and development of hybrids

Interspecific and intraspecific crosses of rice species were made involving the AA genome wild species Oryza meridionalis Ng from Australia, O. nivara Sharma et Shastry, O. rufipogon Griff, the weedy type O. sativa f. spontanea Rosch., and the cultigen O. sativa L. from Asia. Seed set and the number of hybrids obtained from both interspecific and intraspecific crosses were low and no significant differences were observed between the interspecific and intraspecific crosses. In the combination O. meridionalis × O. nivara and O. meridionalis × O. rufipogon, considerable differences in reciprocal crosses were observed, whereas higher seed set and more hybrids were obtained when O. meridionalis was used as the female parent. Pollen stainability and seed fertility of hybrids were very low, averaging between 1% and 9% in both interspecific and intraspecific combinations, except in the O. nivara intraspecific cross of 105386 × 106111, whose hybrid showed 83.0% pollen stainabi lity and 66.5% seed fertility.