Artificial Crosses Research Articles

Artificial hybridization between Robinia pseudoacacia L. and R. pseudoacacia var. monophylla Carr.

Summary Results regarding artifi cial cross- and self-pollination between Robinia pseudoacacia L. and R. pseudoacacia var. monophylla Carr. are reported. Parental clones involved in a diallel mating scheme were selected according to leaf type phenotype and included (1) single-leaf type, (2) 25-leaf type, (3) three-leaf type and (4) common Robinia . Artifi cial pollination proved to be a diffi cult and delicate procedure. A total of 33 pollinations were made that resulted in the formation of 84 pods, of which 24 developed fully and produced 65 seeds. Fifteen seeds were germinated, resulting in the production of two putative fertile hybrids. The success of hybridization was assessed by genetic markers, while parental clones and hybrid progeny were assigned multilocus genotypes. The mode of inheritance of the leaf type trait was studied in open-pollinated families where the monophylla type was the maternal parent. The study indicated that leaf type in the monophylla variety may be associated with major gene effects.

Visualization of genomic relationships in allotetraploid hybrids between Chrysanthemum lavandulifolium X C. chanetii by fluorescence in situ hybridization and genomic in situ hybridization

Artificial cross between Chrysanthemum lavandulifolium (2n=18 diploid) and C. chanetii (2n=36, tetraploid) made succesfully interspecific F1 hybrid (2n=36 tetraploid instead of 2n=27 tripolid) for the first time. The F1 hybrid had 12 signals of 45S rDNA and and four signals of 5S rDNA by FISH. The chromosome complement of the F1 hybrid showed each set of the both parental chromosomes by GISH by using the biotin labeled probe of C. lavandulifolium mixed with approximately 20X blocking DNA of C. chanetii. Eighteen yellow-green colored chromosomes were hybridized with the probe of C. lavandulifolium, that could be involved with C. lavandulifolium, while the other 18 orange-red colored chromosomes were not GISH-hybridized chromosomes with the probe, that could be involved with C. chanetii. The extra nine chromosome set in the hybrids might be resulted due to duplication of the haploid chromosome set of C. lavandulifolium at/after fertilization.

Morphological and AFLP markers for describing genetic relationships among white-oat genotypes

The use of different genetic dissimilarity indicators can help in both the selection of crop improvement strategies and as artificial crosses. The objectives of this work were to estimate the genetic dissimilarity among seven oat genotypes (Avena sativa L.) through molecular (dg) and morphological (dm) markers. Data were obtained from two experiments carried out in Capão do Leão County, RS, Brazil, in 2000. The estimated correlation coefficient (r = 0.33) indicated a low association between dg and dm estimates. The genotypes with similar pedigrees (UPF 16 and UPF 17), with a bootstrapping value of 82.7%, performed the most consistent group (dg) and clustered more closely in both techniques (dg and dm). However, genotypes with similar pedigree clustered in distant groups. Both dissimilarity estimates need to be used in order to obtain a more reliable choice of dissimilar parents, with higher probability of developing promising base populations.

Chloroplast DNA Diversity in Prunus and Its Implication on Genetic Relationships

Chloroplast DNA (cpDNA) in 84 Prunus L. accessions (interspecific hybrids and Prunus species) were analyzed to confirm the maternal origin of the interspecific hybrids of Prunus and to establish genetic relationships among Prunus species. The polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) method, which included amplification of cpDNA regions with three universal primer pairs (K1K2, HK, DT) and subsequent digestion with three restriction enzymes (AluI, HinfI, TaqI), revealed 33 haplotypes for the 84 accessions studied. Fourteen from these cpDNA haplotypes were shared by two or more accessions, and 19 were unique. Accessions sharing the same haplotype have maternal relationships among them, which allowed identity confirmation of maternal progenitors of Prunus interspecific hybrids in these cases. Unweighted pair group method average (UPGMA) and minimum-length spanning tree (MST) analyses were performed based on shared common fragments and the number of mutational differences among the 33 haplotypes, respectively. The cpDNA polymorphisms detected made possible the analysis of genetic relationships among the studied Prunus accessions. Most of the recovered relationships are in agreement with current taxonomic hypotheses and artificial crosses.

VARIABILIDADE GENÉTICA EM TRIGO AFERIDA POR MEIO DA DISTÂNCIA GENEALÓGICA E MORFOLÓGICA

Os caracteres fenotípicos e as informações genealógicas se destacam entre as ferramentas possíveis de serem utilizadas pelos melhoristas na obtenção de estimativa da distância genética entre e dentro das espécies vegetais. Deste modo, o objetivo do trabalho foi estimar a distância genética entre genótipos de trigo sul-brasileiros, por meio do emprego de caracteres fenotípicos e do coeficiente de parentesco, e estabelecer o grau de associação entre tais técnicas. O trabalho foi realizado no município de Pelotas, localizado no Estado do Rio Grande do Sul, Brasil. Dezenove genótipos de trigo foram avaliados por três anos a campo, onde foram aferidos 17 caracteres morfológicos. Estes genótipos foram empregados na estimativa da distância fenotípica e cálculo dos coeficientes de parentesco. Os resultados revelaram ausência de associação entre as duas estimativas de distância genética avaliadas, pelo fato de não haver genealogia comum entre alguns dos genótipos testados, ou ainda, pela inexistência de dados genealógicos disponíveis de alguns genótipos. Ambas as estimativas de distância demonstraram presença de variabilidade genética entre o conjunto de genótipos de trigos sul-brasileiros avaliados. Estas diferenças podem ser exploradas na recomendação de combinações híbridas promissoras para seleção de indivíduos geneticamente superiores, de onde poderão ser obtidas novas constituições gênicas. Genótipos como BRS 177 e Rubi apresentam elevado rendimento de grãos e são divergentes fenotipicamente e genealogicamente em relação aos demais genótipos avaliados, sendo recomendados para utilização em cruzamentos artificiais com a finalidade de promover o incremento da variabilidade genética e aumento da produtividade de grãos em trigo.

Effect of allopolen in artificial crosses of white and yellow endosperm maize hybrids

Effect of allopolen in artificial crosses of white and yellow endosperm maize hybrids

POLLEN VIABILITY AND VARIATION IN <EM>CATHAYA ARGYROPHYLLA</EM>

Aims Cathaya argyrophylla is one of the most endangered conifers endemic to China.Previous studies showed that this species was characterized by unusually low fertility and high embryonic mortality,which may be factors leading to its endangerment.Because knowledge of pollen viability is important for successful reproduction of plant species,we investigated pollen viability in natural populations of C.argyrophylla.Methods We collected pollen samples from 16 individuals of seven populations in two locations,Dayaoshan(DYS)in Sichuan and Huaping(HP)in Guangxi.We evaluated pollen viability using the TTC method and analyzed its variation based on ANOVA.Important findings Pollen viability of C.argyrophylla is comparable to other gymnosperms.Viability was stable in dry and low temperature conditions,and the optional sucrose concentration for pollen germination was about 13%.We found low variation of pollen viability among individuals within populations(p0.05)but significant differentiation between populations within regions and among regions(p0.05).The pollen viability of C.argyrophylla is normal and thus not likely relevant to its endangerment.We proposed artificial crossings between genetically distinct populations as a potential conservation strategy for the population recovery of this endangered species.

Isolation of chromosomes and mutation in the interspecific hybrid between Chrysanthemum boreale and C. vestitum using fluorescence in situ hybridization and genomic in situ hybridization

Interspecific F1 hybrid (2n=30-36) was produced for the first time by artificial cross pollination between Chrysanthemum boreale (2n=18, diploid) and C. vestitum (2n=54, hexaploid). The analysis of fluorescence in situ hybridization (FISH) in the 45S and 5S rDNA sites showed that the F1 hybrid had six and eight signals respectively (instead of eight and six signals of the 45S and 5S rDNA sites respectively) were shown in the F1 hybrid perhaps due to translocation and recombination. Genomic in situ hybridization (GISH) distinguished respective parental chromosomes in the F1 hybrid chromosome complement and showed that at the time of using the biotin labeled probe of C. boreale showed approximately 9-yellow-green-colored chromosomes were hybridized with the probe of C. boreale, might related to C. boreale, 18 orange-colored chromosomes might have a commone chromosome homology between C. boreale and C. vestitum, while the other 9 red-colored were not hybridized chromosomes with the probe and could be of C. vestitum.

Paternal, maternal, and biparental inheritance of the chloroplast genome in Passiflora (Passifloraceae): implications for phylogenetic studies

Patterns of inheritance of the chloroplast genome in Passiflora were analyzed by examining the progeny from both interspecific and intraspecific crosses. Artificial crosses of field-collected material were performed in greenhouses at The University of Texas at Austin. DNA from fresh leaf material was analyzed by Southern blot techniques to identify the donor of the chloroplast genome. Initially, single progeny were analyzed for 11 crosses; two intraspecific crosses demonstrated maternal inheritance, whereas the nine interspecific crosses had paternal inheritance. Subsequently, the donor of the chloroplast genome was determined for multiple progeny in seven crosses. Passiflora oerstedii × P. retipetala showed strict paternal inheritance in all of 17 progeny. A series of five crosses and backcrosses between P. oerstedii and P. menispermifolia demonstrated strictly paternal inheritance. Finally, when 15 progeny were analyzed for the P. costaricensis × P. costaricensis cross, 12 of the 15 showed maternal inheritance, whereas the remaining three were biparental. Interestingly, all interspecific crosses had primarily paternal inheritance, whereas all intraspecific crosses had primarily maternal inheritance. The implications of heteroplasmy on phylogenetic analyses of chloroplast DNA are discussed.

Chloroplast DNA variation in the Turnera sidoides L. complex (Turneraceae): biogeographical implications

AbstractAim To analyse the current geographical structure of chloroplast DNA variation in the Turnera sidoides L. complex in order to establish historical biogeographical hypotheses for the mid‐latitude South American lowlands. During the Quaternary, the climate shifted from tropical humid to cold dry, and the vegetation cover has not been stable. The consequences of these processes on the current distribution of the vegetation of this area have received very little attention.Location The mid‐latitude South American lowlands extend between c. 20 and 40°S and include Uruguay, northern, central and eastern Argentina, southern Brazil, and parts of southern Paraguay and Bolivia. They are surrounded by higher‐elevation systems.Methods Turnera sidoides is a well‐studied polyploid complex of perennial rhizomatous herbs occurring throughout the area of interest. We analysed 321 individuals from 79 populations of the five recognized subspecies. We also included progenies from artificial crosses in order to analyse chloroplast inheritance. After screening sequences for four non‐coding chloroplast DNA regions, the trnL–trnF spacer was selected to characterize the collection.Results Three haplotypes can be easily identified, with each differing from the others in two independent characters. A clear geographic structure is revealed when haplotypes are plotted for the complex as a whole regardless of subspecies and cytotype. Three distinct regions can be identified.Main conclusions We propose three putative refugial areas for the Turnera sidoides complex, which are associated with the orographical systems of the region. Ravines and slopes in the Haedo Cuchilla system in northern Uruguay, the elevations of the western side of the area in Argentina, and the eastern Serranías system in south‐eastern Uruguay may each have served as refugia in which the A, B and C haplotypes became fixed during the drier climatic phases. Biogeographical patterns in the area covered by T. sidoides, particularly east of the Uruguay River, have not previously been analysed from a historical perspective.

Potential Risk of Hybridization in Ex Situ Collections of Two Endangered Species of Sinojackia Hu (Styracaceae)

AbstractSpontaneous hybridization in ex situ facilities can undermine the genetic integrity of ex situ collections and potentially contaminate open‐pollinated seeds or seedlings destined for the reintroduction of endangered plant species into the wild. In the present study, the potential risk of hybridization between two endangered Chinese endemic species, namely Sinojackia xylocarpa Hu and S. rehderiana Hu, which are naturally allopatric species but were conserved ex situ in Wuhan Botanical Garden (WBG), Wuhan, China, were investigated over three consecutive years from 2003 to 2005. The entire overlapping flowering period of the two species was 14–20 d and the two species shared the same pollinator insects during the entire flowering season in WBG. The floral isolation between the two species was not an issue in the ex situ collection at WBG. The results suggest an opportunity for pollen transfer between species and a potential risk of genetic introgression and loss of genetic identity of open‐pollinated seeds produced in the ex situ collection of these two endangered species. An artificial reciprocal cross between S. xylocarpa and S. rehderiana confirmed that the two congener species could readily set seeds, indicating no post‐pollination barriers to hybridization and the importance of spatial isolation as a barrier to inter‐specific crossing. Therefore, to manage these crossable species with overlapping flowering times and shared pollination vectors in ex situ facilities, spatial isolation should be carefully considered to minimize the possibility of spontaneous hybridization.(Managing editor: Wei Wang)

Hybridization studies inSilene subgen.Petrocoptis (Caryophyllaceae)

Silene subgenusPetrocoptis comprises sexual diploid taxa and it is restricted to calcareous cliffs in the Iberian peninsula. Artificial crosses involvingSilene pyrenaica (Bergeret)Mayol etRossello (≡Petrocoptis pyrenaica (Bergeret)Walp.),Silene laxipruinosa Mayol etRossello andS. montserratii subsp.crassifolia (Rouy)Mayol etRossello (≡P. crassifolia Rouy) were attempted to assess the extent of barriers developed within the subgenusPetrocoptis. Usually, intraspecific crosses involving allopatric populations were successful, suggesting that geographically isolated populations are not genetically isolated. Cross-compatibility was noted among the polymorphicS. pyrenaica, which developed fertile F1 hybrids. All other interspecific crosses failed due to cross- or seed-incompatibility. Crossing results agree with available evidence supporting the merging of segregates ofS. pyrenaica within a single taxon.

Effects of pollination distance on reproduction and offspring performance in Hypochoeris radicata: Experiments with plants from three European regions

Fragmentation of habitats has resulted in increased inbreeding for many plant species, while the introduction of foreign seed material for ecological restoration has resulted in crosses between plants from distant populations. Both processes may reduce plant fitness and increase the risk of extinction. Variation in the expression of inbreeding and outbreeding depression has been found among different genotypes and among populations, but little is known about large scale geographical patterns within species. We studied the effects of cross-proximity on seed production and offspring performance in the perennial meadow plant Hypochoeris radicata (Asteraceae) from five populations in each of three European regions (Bohemia in northwest Czechia, Northern Hesse in central Germany, and Salland in the central Netherlands). Five artificial cross types were conducted with varying proximity of mates: selfing (self), within family crosses (WF), within population crosses (WP), between population crosses (BP), and between region crosses (BR), and the offspring were grown in a common garden. Independent of the region of origin of the maternal plant, selfing, WF and BP crosses resulted in lower seed set and germination than WP crosses, indicating partial self-incompatibility, inbreeding depression and reduced performance in the F1 progeny resulting from outbreeding. However, crosses between regions resulted in similar seed set and germination as within population crosses. For late traits, the effects of inbreeding and interpopulation crosses differed among regions. WP crosses exhibited the highest survival, flowering and multiplicative fitness only in progeny from Czech maternal plants. Our results suggest that the sensitivity of populations to introgression may vary among regions and that outbreeding depression does not necessarily increase with interpopulation distance. However, the current study investigated only effects in the F1 in a common garden and outbreeding depression may be stronger in the F2 and in field populations.

A Bayesian Approach for Discriminating Among Alternative Inheritance Hypotheses in Plant Polyploids: The Allotetraploid Origin of Genus Borderea (Dioscoreaceae)

Polyploidy is a common phenomenon occurring in a vast number of land plants. Investigations of patterns of inheritance and the origins of plants (i.e., autopolyploidy vs. allopolyploidy) usually involve cytogenetic and molecular studies of chromosome pairing, chromosome mapping, and marker segregation analysis through experimental crosses and progeny tests. Such studies are missing for most wild species, for which artificial crosses are difficult, not feasible, or unaffordable. We report here a Bayesian method to discriminate between alternative inheritance patterns in the two extant, tetraploid species of the monocot genus Borderea (Dioscoreaceae), which does not involve progeny array tests. Our approach is based on the screening of a large number of SSR genotypes, which were obtained from successful amplifications of 17 microsatellite regions in individuals of both B. chouardii and B. pyrenaica. We tested for tetrasomic vs. disomic modes of inheritance, using the Bayes factor test. Assignment of genotypes under both alternatives could be unequivocally done for 14 and 11 of the 17 studied microsatellite regions in B. chouardii and B. pyrenaica, respectively, totaling 9502 analyzed genotypes. The comparison of posterior probabilities for the two competing hypotheses across the surveyed loci clearly favored a disomic inheritance pattern. Linkage tests indicated that none of the studied SSR loci were in linkage disequilibrium, thus representing independent samples of the Borderea genome. These results, along with previous allozyme data, support the allotetraploid origin of this paleoendemic genus and reveal the lowest reported chromosome base number for the family of the yams.

Herança da resistência à ferrugem da folha da aveia (Puccinia coronata f. sp. avenae Fraser & Led.) em genótipos brasileiros de aveia branca

A ferrugem da folha da aveia é a moléstia mais importante que ataca a cultura da aveia, ocorrendo em praticamente todas as áreas em que a aveia é cultivada. A forma mais indicada para o seu controle é a utilização de cultivares resistentes. Contudo, para que seja alcançada a resistência durável ao patógeno, é necessário que se conheça a genética da resistência à ferrugem da folha em aveia. O objetivo foi determinar a forma de herança da resistência a três isolados de Puccinia coronata f. sp. avenae Fraser & Led., (coletados no sul do Brasil) em genótipos brasileiros de aveia branca. Para a determinação da herança da resistência a cada um dos três isolados, foram utilizadas populações F2 geradas por meio de cruzamentos artificiais, entre genótipos resistentes (R) e suscetíveis (S) e entre genótipos resistentes (R). Desta forma, foram utilizadas populações F2 dos cruzamentos artificiais entre: i) URPEL 15 (R) x UFRGS 7 (S), UPF 16 (R) x UFRGS 7 (S) e URPEL 15 (R) x UPF 16 (R), para a determinação da herança da resistência ao isolado um (1); ii) URPEL 15 (R) x UFRGS 7 (S), UPF 18 (R) x UFRGS 7 (S) e URPEL 15 (R) x UPF 18 (R), para a determinação da herança da resistência ao isolado dois (2); iii) URPEL 15 (R) x UFRGS 7 (S) e URPEL 15 (R) x UPF 18 (S), para a determinação da herança da resistência ao isolado três (3). Os resultados obtidos evidenciaram que o genótipo URPEL 15 apresenta genes dominantes de resistência aos três isolados de ferrugem da folha da aveia avaliados, que o cultivar UPF 16 apresenta um gene recessivo de resistência ao isolado 1 e o cultivar UPF 18 apresenta um gene recessivo de resistência ao isolado 2. E que os genes de resistência apresentados pelos genótipos URPEL 15, UPF 16 e UPF 18, segregam de forma independente.

Hybrid origin of a swordtail species (Teleostei:Xiphophorus clemenciae) driven by sexual selection

The swordlike exaggerated caudal fin extensions of male swordtails are conspicuous traits that are selected for through female choice. Swords are one of only few examples where the hypothesis of a pre-existing bias is believed to apply for the evolution of a male trait. Previous laboratory experiments demonstrated that females prefer males with longer swords and even females from some swordless species show an affiliation for males of sworded species. Earlier phylogenetic studies based on maternally inherited mitochondrial DNA placed the sworded southern swordtail Xiphophorus clemenciae with swordless platies, contradicting its morphology-based evolutionary affinities. The analyses of new nuclear DNA markers now recover its traditional phylogenetic placement with other southern swordtails, suggesting that this species was formed by an ancient hybridization event. We propose that sexual selection through female choice was the likely process of hybrid speciation, by mating of platy females with males of an ancestral swordtail lineage. In artificial crosses of descendent species from the two potential ancestral lineages of X. clemenciae the hybrid and backcross males have swords of intermediate lengths. Additionally, mate choice experiments demonstrate that hybrid females prefer sworded males. These experimental lines of evidence make hybridization through xeno-specific sexual selection by female choice the likely mechanism of speciation.

Inheritance Studies Implicate a Genetic Mechanism for Apparent Sex Reversal in Chinook Salmon

AbstractThe apparent increase in altered sexual differentiation in Pacific salmon Oncorhynchus spp. is a growing concern. Previous studies suggest that incongruence between genetic and phenotypic sex in Chinook salmon O. tshawytscha may be a result of altered sexual differentiation through exposure to endocrine‐disrupting chemicals (EDCs). Artificial crosses between genotypically normal Chinook salmon, or between genotypically normal males and apparent sex‐reversed males (XY females), were performed to test the validity of OtY1 and growth hormone pseudogene (GHΨ) genetic markers as indicators of phenotypic sex in fall‐run Chinook salmon. The offspring produced were genotyped with the Y‐chromosome‐specific markers and were dissected to observe gonad morphology. The results of the breeding experiments indicate that approximately half of the phenotypic female offspring of XY females have a male genotype according to both Y‐chromosome markers. These results refute an earlier hypothesis that phenotypic female Chinook salmon with a male genotype (XY females) are the result of altered sexual differentiation caused by EDC exposure. Instead, either the OtY1 and GHΨ markers have recombined between the Y and X chromosomes or an autosome, or a mutation has inactivated the sex‐determining region of the Y chromosome. In none of the 2,384 Chinook salmon evaluated did the genetic markers contradict one another in a single individual. These results present evidence that both OtY1 and the GHΨ genetic markers appear to not be diagnostic for sex in fall‐run Chinook salmon in the Central Valley of California.

Variation analysis of seed and seedling traits of cross combination progenies in Populus

Twenty-five species and hybrids in Populus were used as parents, and 26 cross combinations, including more than 5 000 seedlings, were obtained by artificial cross breeding. The length of infructescence, number of seeds per infructescence, thousand-seed weight, germination rate of seeds among these cross combinations were tested. The results indicated that the cross combinational effects were significant for these traits, and demonstrated that the length of infructescence, thousand-seed weight were positively affected by female parent. In addition, seedling height, diameter above ground, diameter at breast height (DBH) of 17 cross combination progenies were investigated. The analysis of mean and standard deviation of these three traits showed that seedling height, diameter above ground, DBH had extensive variation among combinations and individuals within combination. Variance analysis and estimate of heritability indicated that the three traits had wide variation and were controlled by heredity. It was feasible to select superior cross combinations and seedlings. Further more, the result of multiple comparison showed that P. deltoides ‘Lux’ × P. deltoides ‘D324’, P. ussuriensis cl. ‘U4’ × P. deltoides ‘T66’, P. ussuriensis cl. ‘U4’ × P. deltoides ‘T26’, P. deltoides ‘Lux’ × P. ussuriensis cl. ‘U3’, (P. tomentosa × P. bolleana) × (P. alba × P. glandulosa), (P. alba × P. tomentosa) × (P. alba × P. glandulosa), and (P. alba × P. glandulosa ‘No. 2’) × P. tomentosa ‘Lumao 50’ were superior cross combinations with higher growth rate. Finally, 123 elite seedlings were selected for further test.

GENEROSE: GENETIC EVALUATION OF EUROPEAN ROSE RESOURCES FOR CONSERVATION AND HORTICULTURAL USE

GENEROSE: GENETIC EVALUATION OF EUROPEAN ROSE RESOURCES FOR CONSERVATION AND HORTICULTURAL USE

How selfing and intra- and interspecific crossing influence seed set, morphology and ploidy level in Euphrasia: An experimental study of species occurring in the Alps of Switzerland

Annual alpine species rely on selfing rather than on cross-pollination for successful reproduction. However, insect visits may occasionally cause cross-pollination not only within but also between closely related species. The aim of this study was to investigate four species of Euphrasia for their efficiency in spontaneous selfing and their success in intra- and interspecific crossing. We used the seed sets that followed spontaneous selfing and artificial cross- and selfpollination to measure the breeding success. We compared the morphological characters of species and hybrids and determined their ploidy level using flow cytometry. We verified the hybridogenous origin of plants resulting from interspecific crosses using RAPD banding patterns. While spontaneous seed set was high in the two small-flowered species, seed set in the large-flowered species was small and affected by external circumstances. We obtained F1 and F2 hybrids from interspecific crosses of two diploid species and detected polyploid individuals in both generations.