Using SSR markers for hybrid identification and resource management in Vietnamese <Emphasis Type="Italic">Acacia</Emphasis> breeding programs

We used a set of 16 SSR markers to check the identity of pure-species and hybrid clones in Vietnam’s Acacia auriculiformis, Acacia mangium, and acacia hybrid (A. mangium × A. auriculiformis) breeding programs. The statistics package HIest, applied to a large synthesized population, enabled accurate allocation of genotypes to the two pure species, F₁ and F₂ inter-specific hybrids and backcrosses, based on estimates of hybridity and heterozygosity. The hybridity status of putatively pure A. mangium and A. auriculiformis clones in adjacent clonal seed orchards was checked. Four out of 100 clones selected as A. mangium were found to be backcrosses (A. mangium × F₁ inter-specific hybrid) while out of 96 clones selected as A. auriculiformis, two were F₁ hybrids and two were backcrosses (A. auriculiformis × F₁ hybrid). The markers were then applied to check the hybridity status of 160 putative acacia F₁ hybrid genotypes that had been selected on morphological criteria from open-pollinated progenies collected from A. auriculiformis and A. mangium parents. Many selections based on morphology were found to be mistaken. Only thirteen of 63 clones originating from A. auriculiformis mothers were F₁ hybrids, four were backcrosses, and the remaining 46 were pure A. auriculiformis. Fewer mistakes were evident for clones selected from A. mangium mothers, with 82 out of 89 clones confirmed as F₁ hybrids, three as backcrosses, and four as pure A. mangium. The occurrence of F₁ hybrids and backcrosses in pure-species seed orchards and their progeny shows that inter-species contamination is an issue requiring management in both pure-species and in hybrid breeding of these species in Vietnam. Examination of genetic distances among verified clones showed patterns of relatedness that were consistent with pedigree records. Implications for resource management as well as for breeding and clonal selection strategies are considered.     

THE RELATIONSHIPS BETWEEN MALE AND FEMALE FERTILITY AND AMONG TAXA IN DIPLOID WHEATS

Pollen stainability appears to be a reliable indication of the ultimate seed set in diploid interspecific hybrid and backcross populations in Triticum L. The correlation between percent pollen stained and number of seeds set is positive and highly significant (r = 0.92). Estimates of male and female fertility in the hybrids and backcrosses are interpreted to indicate that the domesticated diploid Triticum monococcum L. and wild diploid T. boeoticum Boiss. em. Schiem, are one and the same species, and that T. urartu Tum. is not a variety of monococcum or boeoticum, but rather a separate species. The F₁ hybrids and backcrosses between monococcum and boeoticum are normally male and female fertile. The F₁ hybrids between monococcum and urartu are completely sterile and complete to partial sterility exists in backcrosses.     

Unidirectional hybridization and reproductive barriers between two heterostylous primrose species in north-west Yunnan,China

Background and Aims

Heteromorphy in flowers has a profound effect on breeding patterns within a species, but little is known about how it affects reproductive barriers between species. The heterostylous genus Primula is very diverse in the Himalaya region, but hybrids there have been little researched. This study examines in detail a natural hybrid zone between P. beesiana and P. bulleyana.

Methods

Chloroplast sequencing, AFLP (amplified fragment length polymorphism) markers and morphological comparisons were employed to characterize putative hybrids in the field, using synthetic F₁s from hand pollination as controls. Pollinator visits to parent species and hybrids were observed in the field. Hand pollinations were conducted to compare pollen tube growth, seed production and seed viability for crosses involving different morphs, species and directions of crossing.

Key Results

Molecular data revealed all hybrid derivatives examined to be backcrosses of first or later generations towards P. bulleyana: all had the chloroplast DNA (cpDNA) of this species. Some individuals had morphological traits suggesting they were hybrids, but they were genetically similar to P. bulleyana; they might have been advanced generation backcrosses. Viable F₁s could not be produced with P. bulleyana pollen on P. beesiana females, irrespective of the flower morphs used. Within-morph crosses for each species had very low (<10 %) seed viability, whereas crosses between pin P. bulleyana (female) and pin P. beesiana had a higher seed viability of 30 %. Thus genetic incompatibility mechanisms back up mechanical barriers to within-morph crosses in each species, but are not the same between the two species. The two species share their main pollinators, and pollinators were observed to fly between P. bulleyana and hybrids, suggesting that pollinator behaviour may not be an important isolating factor.

Conclusions

Hybridization is strongly asymmetric, with P. bulleyana the only possible mother and all detected hybrids being backcrosses in this direction. Partial ecological isolation and inhibition of heterospecific pollen, and possibly complete barriers to F₁ formation on P. beesiana, may be enough to make F₁ formation very rare in these species. Therefore, with no F₁ detected, this hybrid zone may have a finite life span as successive generations become more similar to P. bulleyana.     

Hybridization rate and climate change: are endangered species at risk?

Many species are altering their geographic range due to climate change creating new sympatric populations of otherwise allopatric populations. We investigated whether climate change will affect the distribution and thus the pattern of hybridization between two pairs of closely related damselfly species [Ischnura damula and I. demorsa, and I. denticollis and I. gemina (this, an endangered species)]. Thus, we estimated the strength of pre and postmating reproductive barriers between both pairs of species, and we predicted future potential distribution under four different Global Circulation Models and a realistic emissions scenario of climate change by using maximum entropy modelling technique. Our results showed that reproductive isolation (RI) is complete in I. damula × I. demorsa individuals: F₁ (first generation) hybrids are produced but do not reach sexual maturation. However, RI in I. denticollis × I. gemina hybrids is high but incomplete and unidirectional: only I. gemina females produced F₁ hybrids which mate with males and females of I. denticollis and between them producing BC₁ (backcrosses) and F₂ (second generation) viable hybrids. Maximum entropy models revealed a northern and westward shift and a general reduction of the potential geographic ranges. Based on the pattern of hybridization, for I. damula and I. demorsa there is a current threat as well as a rapid displacement and/or extinction of I. gemina by I. denticollis. However, the current pattern of extinction may not continue due to the contraction in ranges of the four species.     

The possible origin of thick stem in Chinese wild soybean (Glycine soja)

Thicker, erect stem and enlarged seeds are characteristic of the domestication of cultivated soybeans (Glycine max) from its progenitor, wild soybean (G. soja). Wild soybeans have different stem thicknesses but the thick stem as defined here appears in a small number of small-seeded wild soybeans (≤2.0 g/100-seeds) in China. However, little attention has been paid to this phenomenon in considering the origin of thick stem in wild soybean. Here, we addressed this question through the study of a mixed field of wild, semi-wild and cultivated soybeans. Thick-stemmed samples had lower sensitivity to light period, higher mean genetic diversity (H _e = 0.090, H = 0.535) and higher mean multilocus outcrossing rate (t _m = 9.77 %), while thin-stemmed plants were the opposite (H _e = 0.029, H = 0.416) and lower mean outcrossing rate (t _m = 5.88 %). F statistics calculations indicated that there was genetic differentiation between the thin and thick stems. UPGM cluster analysis showed that not only were thick-stemmed wild soybeans genetically different from thin-stemmed ones, but they were also genetically closer to semi-wild soybean, to varying degrees completely dependent on seed size. These data strongly implied that the plants with thick stems had more complicated genetic backgrounds than the thin-stemmed ones, and that they were related to cultivated soybeans. This study suggests that if plants have distinctly thick stems (an average 2.5-fold thicker than other thin-stemmed plants) or stems similar to semi-wild plants and/or near to local soybeans in a natural wild population adjacent to farmlands, such plants could be cultivar-introgressive offspring.     

Use of single nucleotide polymorphisms identifies backcrossing and species misidentifications among three San Francisco estuary osmerids

Two threatened osmerid species native to the San Francisco Estuary (SFE)—Delta Smelt (Hypomesus transpacificus) and Longfin Smelt (Spirinchus thaleichthys)—are subject to broad human influence, including significant habitat alteration and the presence of the introduced osmerid, Wakasagi (Hypomesus nipponensis). The identification of these closely related species and their hybrids is difficult in field collected specimens which are subject to damage through handling and may be difficult to identify morphologically, especially when young. In addition, it is known that these three species hybridize, but the extent and effect of hybridization is difficult to quantify and monitor. We developed assays for 24 species-specific single nucleotide polymorphisms (SNPs) that identify whether a sample is a pure species (Delta Smelt, Longfin Smelt, or Wakasagi), a first generation (F₁) hybrid, or a backcross. We used this SNP panel to genetically identify wild osmerids collected in Yolo Bypass from 2010 to 2016 and detected nine Delta Smelt × Wakasagi F₁ hybrids and two Wakasagi × (Delta Smelt × Wakasagi) backcross hybrids; all assayed hybrids had Wakasagi as the maternal parent. The backcrossing into Wakasagi suggests that hybridization may only occur in one direction and thus preclude introgression to Delta Smelt. We also found substantial morphological field misidentifications (32.7%) in the Yolo Bypass samples resulting in more Wakasagi and fewer Delta Smelt than previously recorded when based on morphology. The SNP panel described in this study constitutes a valuable resource for monitoring hybridization in the SFE and assigning species identifications with accuracy and efficiency.     

Interspecific hybridisation and interaction with cultivars affect the genetic variation of Ulmus minor and Ulmus glabra in Flanders

Interspecific hybridisation and gene flow from cultivated plants may have profound effects on the evolution of wild species. Considering the cultural history and past use of Ulmus minor and Ulmus glabra trees in Flanders (northern Belgium), we investigated the extent of human impact on the genetic variation of the remaining, supposedly indigenous elm populations. We therefore examined the rate of interspecific hybridisation, which is expected to be higher under human influence, the occurrence of clones within and among locations, the presence of cultivars and their possible offspring. Based on results produced using 385 amplified fragment length polymorphic (AFLP) markers, 46 % of the 106 investigated Flemish elms appeared to be F1 hybrids or backcrosses to one of the parent species, while no F2 hybrids (F1?×?F1 progeny) were found. Clonality was mainly found among U. minor and hybrids, which are more likely to form root suckers or sprouts as opposed to U. glabra. The majority of the studied locations (76 % of the locations with multiple samples) showed evidence of clonal reproduction. Several, sometimes distant, locations shared a multilocus lineage. We also found indications of gene flow from cultivated elms into native species. It is conceivable that reproductive material has been moved around extensively, obscuring the natural genetic structure of the elm populations. The results help guide the Flemish elm genetic resources conservation programme.     

Evidence for introgressive hybridization of wild common quail (Coturnix coturnix) by domesticated Japanese quail (Coturnix japonica) in France

Many cases of introgressive hybridization have been reported among birds, particularly following introduction to the natural environment of individuals belonging to non-native similar taxa. This appears to be the case for common quail (Coturnix coturnix) in France where wild populations artificially come into contact with domesticated Japanese quail (Coturnix japonica) raised for meat and egg production but sometimes released for hunting purposes. In order to highlight the possible existence of gene flows between both taxa, a comparison of nuclear (25 microsatellite loci) and mitochondrial (sequencing and RFLP) DNA polymorphisms was performed on 375 common quails (from France, Spain and Morocco) and 140 Japanese quails (from France and Japan). Genetic diversity was assessed, and analyses (Factorial Correspondence Analysis, Bayesian admixture) of molecular polymorphisms revealed clear differentiation between the two taxa, making it possible to detect for hybrids among quails sampled in the wild. Eight birds expected to be common quail were found to be two pure Japanese quail, one probable backcross to C. japonica, three F1/F2 hybrids, and two probable backcrosses to Coturnix coturnix. These results show that Japanese quails were released and suggest that the two taxa hybridize in the wild. They confirm the urgent need for preventing the release of pure Japanese or hybrid quails to preserve the genetic integrity of C. coturnix. The tools developed for this study should be useful for accurate monitoring of wild quail populations within the framework of avifauna management programs.     

Doubled haploids of novel trigenomic Brassica derived from various interspecific crosses

To develop doubled haploid (DH) mapping populations of hexaploid Brassica, 10 F₁ hybrids derived from crosses between allohexaploid Brassica parents were evaluated in this study. The allohexaploid Brassica parents were selfed progenies of unique interspecific crosses between Brassica rapa (genome AA) × B. carinata (BBCC), B. nigra (BB) × B. napus (AACC), and a complex cross between B. juncea (AABB), B. napus and B. carinata, with relatively stable chromosome number (2n = 54). Hexaploid status and chromosome behavior during meiosis I in four promising F₁ hybrids were assessed using microscopy and flow cytometry, and progeny were obtained following microspore culture. Hybrids H11-2 and H16-1 demonstrated higher amenability for embryo generation, plantlet regeneration, and frequency of production of DH microspore-derived progeny of hexaploid DNA content (6x) compared to hybrids H08-1 and H24-1. A total of 370 6x DH progeny were selected out of 693 plantlets from H11-2, 241/436 from H16-1, 23/54 from H08-1, and 21/56 from H24-1. DH progenies of hybrids H11-2 and H16-1 were then designated as promising mapping populations of a new hexaploid Brassica species.     

Patterns of hybridization and asymmetrical gene flow in hybrid zones of the rare Eucalyptus aggregata and common E. rubida

The patterns of hybridization and asymmetrical gene flow among species are important for understanding the processes that maintain distinct species. We examined the potential for asymmetrical gene flow in sympatric populations of Eucalyptus aggregata and Eucalyptus rubida, both long-lived trees of southern Australia. A total of 421 adults from three hybrid zones were genotyped with six microsatellite markers. We used genealogical assignments, admixture analysis and analyses of spatial genetic structure and spatial distribution of individuals, to assess patterns of interspecific gene flow within populations. A high number of admixed individuals were detected (13.9–40% of individuals), with hybrid populations consisting of F₁ and F₂ hybrids and backcrosses in both parental directions. Across the three sites, admixture proportions were skewed towards the E. aggregata genetic cluster (x=0.56–0.65), indicating that backcrossing towards E. aggregata is more frequent. Estimates of long-term migration rates also indicate asymmetric gene flow, with higher migration rates from E. aggregata to hybrids compared with E. rubida. Taken together, these results indicate a greater genetic input from E. aggregata into the hybrid populations. This asymmetry probably reflects differences in style lengths (E. rubida: ∼7 mm, E. aggregata: ∼4 mm), which can prevent pollen tubes of smaller-flowered species from fertilizing larger-flowered species. However, analyses of fine-scale genetic structure suggest that localized seed dispersal (<40 m) and greater clustering between hybrid and E. aggregata individuals may also contribute to directional gene flow. Our study highlights that floral traits and the spatial distributions of individuals can be useful predictors of the directionality of interspecific gene flow in plant populations.     

Increased pre-dispersal seed predation in sunflower crop-wild hybrids

The fitness of crop-wild hybrids can influence gene flow between crop and wild populations. Seed predation levels in crop-wild hybrid plants can be an important factor in determining plant fitness, especially in large-seeded crops such as sunflower. To determine patterns of pre-dispersal seed predation, seeds were collected from wild sunflowers (Helianthus annuus L.) and wild×crop F₁ hybrids at three experimental field sites in eastern Kansas. Seed heads were dissected and each seed was counted and scored for categories of seed damage by lepidopteran and coleopteran larvae. Hybrid seed heads showed significantly higher levels of insect-damaged seeds. The average hybrid plant had 36.5% of its seeds (or 45.1 seeds per plant) eaten by insect larvae while the average wild plant lost only 1.8% (or 95 seeds) to seed predators. Hybrid populations had higher levels of total insect damage even when date of flowering, flower head diameter, and the number of open heads within the study site were accounted for. These results suggest that the reduced fecundity of F₁ crop-wild sunflower hybrids demonstrated in other studies may be augmented by the increased seed predation in hybrid flower heads. Fecundity estimates of crop-wild hybrid and wild plants that disregard differential seed predation levels may not accurately reflect the actual relative contributions of hybrid and wild plants to future generations. Received: 21 December 1998 / Accepted: 8 July 1999     

Molecular and morphological evidence of natural interspecific hybridization between the uncommon Eucalyptus aggregata and the widespread E. rubida and E. viminalis

Human activities can promote increased hybridization in the genus Eucalyptus with potentially detrimental consequences for the persistence of rare species. However, many hybrid combinations have not been investigated with combined use of genetic markers and morphology. We assessed the efficiency of the STRUCTURE program and morphological intermediacy for identifying hybrids between the uncommon tree, Eucalyptus aggregata, which putatively hybridizes with the common congeners, E. rubida and E. viminalis in south-eastern Australia. We sampled 1,005 seedlings across 27 populations, all seedlings were genotyped at 6 allozyme loci and scored for 22 stem and leaf characters. Both marker sets confirmed that E. aggregata is hybridizing with both E. rubida and E. viminalis. Allozymes revealed hybrids from E. aggregata trees in 88% of populations and hybrids comprised 7.3% of all seedlings. Both genetics and morphology indicated that ~50% were likely to be F₁ hybrids, and both simulations and morphological characteristics indicated that the remainder were mostly backcrosses. Morphological analysis correctly distinguished 71% of F₁ hybrids from parentals and was least accurate when dealing with potential backcrosses (50% success). Hence, techniques using genetic data (no prior information) and the assessment of appropriate admixture thresholds through simulations provided the most accurate estimates of hybrid frequency. In this study, potential introgression and the high frequency of hybrids in small populations (~30%), suggests that hybridization should be considered in the management and conservation of E. aggregata.     

Interspecific hybridization between common and tepary beans: increased hybrid embryo growth,fertility, and efficiency of hybridization through recurrent and congruity backcrossing

Cultivated common bean (Phaseolus vulgaris L.) and tepary bean (Phaseolus acutifolius A. Gray) genotypes possessing desirable agronomic traits were hybridized. The F₁ hybrids were backcrossed twice with the common bean (i.e., recurrent backcrossing). Also, alternate backcrosses with common and tepary beans (i.e., congruity backcrossing) were carried out. Embryo culture was necessary for all initial interspecific crosses, and its requirement was proportionally lower when the common bean was used as the recurrent parent and as the last parent of congruity backcrosses. Modification of the embryo culture technique was necessary to produce congruity hybrids. Effects of both tepary and common bean genotypes on the success rate of hybridization were observed. Tepary accession G 40001 and common bean cultivar ICA Pijao facilitated interspecies hybridization. Growth of hybrid embryos before rescue, recovery of mature hybrid plants, and the vigor and fertility of F₁ hybrids all increased with increased recurrent and congruity backcrosses and intermatings between male-sterile F₁ and selected fertile F₂ plants of the third and fifth congruity backcrosses. Introgression of tepary genes was verified by means of seed protein electrophoretic analysis and morphological markers. The results suggest that congruity backcrossing can help to gradually reduce or overcome P. vulgaris x P. acutifolius hybridization barriers such as genotype incompatibility, early embryo abortion, hybrid sterility, and lower frequencies of hybridization.     

DEVELOPMENTAL STABILITY,FITNESS, AND TRAIT SIZE IN LABORATORY HYBRIDS BETWEEN EUROPEAN SUBSPECIES OF THE HOUSE MOUSE

The effects of hybridization on developmental stability and size of tooth characters were investigated in intersubspecific crosses between random-bred wild strains of the house mouse (Mus musculus domesticus and M. m. musculus). Fluctuating asymmetry (FA) and trait size were compared within and between parental, F₁, backcross, and F₂ hybrid groups. The relationship between FA and reproductive fitness within the F₁ hybrids was also studied. The results indicated that both FA and character size levels differed significantly between the two subspecies. The F₁ hybrids and the recombined groups (backcrosses and F₂ hybrids) showed heterosis for both parameters. No significant differences in the FA of fertile and sterile F₁ hybrid individuals were found. Comparison of the FA levels obtained in this study with those found in wild populations from the hybrid zone in Denmark showed that the levels of FA were lower in laboratory-bred samples than in the wild populations. This study provides further evidence that, in hybrids, the developmental processes underlying most of the morphological traits we studied benefit from a heterotic effect, despite the genomic incompatibilities between the two European house mice revealed by previous genetical and parasitological studies.     

Assessing patterns of hybridization between North Atlantic eels using diagnostic single-nucleotide polymorphisms

The two North Atlantic eel species, the European eel (Anguilla anguilla) and the American eel (Anguilla rostrata), spawn in partial sympatry in the Sargasso Sea, providing ample opportunity to interbreed. In this study, we used a RAD (Restriction site Associated DNA) sequencing approach to identify species-specific diagnostic single-nucleotide polymorphisms (SNPs) and design a low-density array that combined with screening of a diagnostic mitochondrial DNA marker. Eels from Iceland (N=159) and from the neighboring Faroe Islands (N=29) were genotyped, along with 94 larvae (49 European and 45 American eel) collected in the Sargasso Sea. Our SNP survey showed that the majority of Icelandic eels are pure European eels but there is also an important contribution of individuals of admixed ancestry (10.7%). Although most of the hybrids were identified as F1 hybrids from European eel female × American eel male crosses, backcrosses were also detected, including a first-generation backcross (F1 hybrid × pure European eel) and three individuals identified as second-generation backcrosses originating from American eel × F1 hybrid backcrosses interbreeding with pure European eels. In comparison, no hybrids were observed in the Faroe Islands, the closest bodies of land to Iceland. It is possible that hybrids show an intermediate migratory behaviour between the two parental species that ultimately brings hybrid larvae to the shores of Iceland, situated roughly halfway between the Sargasso Sea and Europe. Only two hybrids were observed among Sargasso Sea larvae, both backcrosses, but no F1 hybrids, that points to temporal variation in the occurrence of hybridization.     

Genetic distance as a predictor of heterosis and hybrid performance within and between heterotic groups in sunflower

Heterosis is significant for seed yield and is one of the driving forces behind the hybrid seed industry in cultivated sunflower (Helianthus annuus L). Heterotic groups in sunflower, if any other than the female and male inbred-line groups exist, have not been well studied or described. The primary aims of this study were to assess the utility and validity of a series of proposed heterotic groups and estimate correlations between genetic distance, heterosis, and hybrid performance for seed yield in sunflower. Fortytwo female by male heterotic group (A × R) and 81 female by female heterotic group (A × B) single-cross hybrids were grown in Corvallis, Ore., and Casselton, N.D., in 1996 and 1997. Heterosis was significant for seed yield and plant height but not for seed oil concentration and days to flowering. Genetic distances were significantly correlated with hybrid seed yield when estimated from AFLP fingerprints (G _D) (r = 0.63 for A × R and 0.79 for A × B hybrids), but not from coancestries (G _C) (r = -0.02 for A × R and 0.54 for A × B hybrids). G _D (R ² = 0.4) was a poor predictor of hybrid seed yield. The proposed heterotic groups in sunflower seem to have utility, but do not seem to be as strongly differentiated as those in corn (Zea mays L.). The highest-yielding hybrids were from the B_C× R_B heterotic pattern; however, several B_C× B_C hybrids (within-group hybrids) were among the top-yielding hybrids. The outstanding performance of certain B_C× B_C hybrids casts some doubt on the validity of the B_C group. Substantial genetic diversity seems to be present within and between heterotic groups in sunflower. Received: 1 September 1998 / Accepted: 14 September 1999     

Equisetum (Equisetaceae) species or hybrids? ISSR fingerprinting profiles help improve diagnoses based on morphology and anatomy

The applicability of “inter-simple sequence repeats” (ISSR)-PCR as a molecular character complex for differentiation of Equisetum taxa is described with a special focus on the detection of hybrids. All Central European Equisetum species and the four most frequent hybrids are considered: E. arvense, E. fluviatile, E. telmateia, E. palustre, E. sylvaticum, E. pratense, E. × litorale, E. ramosissimum, E. hyemale, E. variegatum, E. × moorei, E. × trachyodon and E. × meridionale. The ISSR banding patterns are highly typical for each species. The positions of the clusters of hybrid taxa prove their hybrid origin and enable identification of the parental species. Genetic similarities of populations suggest that in some species vegetative reproduction predominates (e.g. E. arvense), whereas for others (e.g. E. telmateia) sexual reproduction seems to be more frequent. In addition to the molecular analyses, the characteristics of stem cross sections of the four hybrids and their parental species are shown and discussed.     

Genetic differentiation in Elaeocarpus photiniifolia (Elaeocarpaceae) associated with geographic distribution and habitat variation in the Bonin (Ogasawara) Islands

Gene flow between populations in different environmental conditions can be limited due to divergent natural selection, thus promoting genetic differentiation. Elaeocarpus photiniifolia, an endemic tree species in the Bonin Islands, is distributed in two types of habitats, dry scrubs and mesic forests. We aim to elucidate the genetic differentiation in E. photiniifolia within and between islands and between the habitat types. We investigated genotypes of 639 individuals from 19 populations of E. photiniifolia and its closely-related E. sylvestris at 24 microsatellite loci derived from expressed sequence tags. The data revealed genetic differentiation (1) between E. photiniifolia and E. sylvestris (0.307 ≤ F _ST ≤ 0.470), (2) between the E. photiniifolia populations of the Chichijima and Hahajima Island Groups in the Bonin Islands (0.033 ≤ F _ST ≤ 0.121) and (3) between E. photiniifolia populations associated with dry scrubs and mesic forests in the Chichijima Island Group (0.005 ≤ F _ST ≤ 0.071). Principal coordinate analysis and Bayesian clustering analysis also showed that genetically distinct groups were associated with the habitat types, and isolation by distance was not responsible for the genetic differentiation. These findings suggest that E. photiniifolia is divided into genetically differentiated groups associated with different environmental conditions in the Bonin Islands.     

Molecular characterization of Alr1105 a novel arsenate reductase of the diazotrophic cyanobacterium Anabaena sp. PCC7120 and decoding its role in abiotic stress management in Escherichia coli

This paper constitutes the first report on the Alr1105 of Anabaena sp. PCC7120 which functions as arsenate reductase and phosphatase and offers tolerance against oxidative and other abiotic stresses in the alr1105 transformed Escherichia coli. The bonafide of 40.8 kDa recombinant GST+Alr1105 fusion protein was confirmed by immunoblotting. The purified Alr1105 protein (mw 14.8 kDa) possessed strong arsenate reductase (Km 16.0 ± 1.2 mM and Vmax 5.6 ± 0.31 μmol min^?1 mg protein^?1) and phosphatase activity (Km 27.38 ± 3.1 mM and Vmax 0.077 ± 0.005 μmol min^?1 mg protein^?1) at an optimum temperature 37 °C and 6.5 pH. Native Alr1105 was found as a monomeric protein in contrast to its homologous Synechocystis ArsC protein. Expression of Alr1105 enhanced the arsenic tolerance in the arsenate reductase mutant E. coli WC3110 (?arsC) and rendered better growth than the wild type W3110 up to 40 mM As (V). Notwithstanding above, the recombinant E. coli strain when exposed to CdCl₂, ZnSO₄, NiCl₂, CoCl₂, CuCl₂, heat, UV-B and carbofuron showed increase in growth over the wild type and mutant E. coli transformed with the empty vector. Furthermore, an enhanced growth of the recombinant E. coli in the presence of oxidative stress producing chemicals (MV, PMS and H₂O₂), suggested its protective role against these stresses. Appreciable expression of alr1105 gene as measured by qRT-PCR at different time points under selected stresses reconfirmed its role in stress tolerance. Thus the Alr1105 of Anabaena sp. PCC7120 functions as an arsenate reductase and possess novel properties different from the arsenate reductases known so far.     

Reduced clonal reproduction indicates low potential for establishment of hybrids between wild and cultivated strawberries (Fragaria vesca × F. × ananassa)

The genus Fragaria (Rosaceae) contains 24 species, including hybrid species such as the garden strawberry (Fragaria × ananassa Duch.). Natural hybridization between Fragaria species has repeatedly been reported, and studies on the hybridization potential between F. × ananassa and its wild relatives have become increasingly important with the outlook for genetically modified garden strawberries. In Europe, a candidate species for hybridization with garden strawberries is the common woodland strawberry (Fragaria vesca L.). Although a previous field survey indicated that the potential for hybridization between F. vesca and F. × ananassa is low, it is not clear whether the lack of natural hybrids is caused by known pre- and postzygotic barriers, or whether hybrid plants lack the fitness to establish in natural F. vesca populations. We grew different F. vesca and F. vesca × F. × ananassa hybrid clones with and without competition in a greenhouse and assessed biomass production, clonal reproduction, and sexual reproduction of plants. While some hybrid clones exceeded F. vesca in biomass production, general clonal reproduction was much lower and delayed in hybrids. Furthermore, hybrids were sterile. These results demonstrate a mechanism by which the general lack of F. vesca × F. × ananassa hybrids in natural habitats can be explained, in addition to the known low hybridization potential between garden and woodland strawberries. We conclude that hybrids have a competitive disadvantage against co-occurring F. vesca plants due to inferior and delayed clonal reproduction, and that the potential for hybrid establishment under natural conditions is low.