The predictability of traits and ecological interactions on 17 different crosses of hybrid oaks

Herbivory on hybrid plants has the potential to affect patterns of plant evolution, such as limiting gene-flow through hybrids, and can also affect herbivore biodiversity. However, few studies have surveyed multiple hybrid species to identify phylogenetic patterns in the inheritance of plant traits that may drive herbivory. We surveyed 15 leaf traits and patterns of chewing, mining, and galling herbivory in a common garden of 17 artificially crossed hybrid oak species and each of their parental species over a 2-year period. Using a phylogeny of oaks, we tested whether hybrids that resulted from more divergent parents received more herbivory than those derived from closely related parents (as would be predicted by a build-up of incompatibilities in defensive systems over evolutionary time) and found only marginal evidence in support of this. We found that chewing damage to hybrids was weakly predicted by the relatedness of a parental species to the single native oak. The levels of chewing and mining herbivory on hybrids were typically intermediate to those of their parental species, though less than the parental mean for chewing damage in 2008. Most leaf traits of hybrids were also intermediate to those of their parental species. There was no clear pattern in terms of an association between 11 species of cynipid gall wasps and hybrids. The patterns of (1) intermediate levels of herbivory on hybrids and (2) no trend in herbivory on hybrids based on the phylogenetic relatedness of parental species suggest that herbivory may not play a general role in limiting hybrid fitness (and thus gene-flow through hybrids) in oaks.     

HYBRIDS AND PHYLOGENETIC SYSTEMATICS I. PATTERNS OF CHARACTER EXPRESSION IN HYBRIDS AND THEIR IMPLICATIONS FOR CLADISTIC ANALYSIS

Interspecific hybridization is considered common among plants, but the methods of cladistic systematics produce only divergently branching phylogenetic hypotheses and thus cannot give the correct phylogeny if an analysis includes hybrids. Empirical studies of the impact of known hybrids on phylogenetic analysis are lacking, and are necessary to begin to understand the problems that we face if hybrids are often included in cladistic analysis. Examination of the implications of hybrids for cladistics must begin with patterns of character expression in hybrids. This study includes 17 hybrids and their nine parental taxa that are Central American species of Aphelandra (Acanthaceae), analyzed using a set of 50 morphological characters. The hybrids are overwhelmingly intermediate as quantitatively scored for phylogenetic analysis. They express maternal and paternal, and primitive and derived characters in equal frequencies, showing no evidence of predominant inheritance of derived character states as has been assumed by most cladists who have considered hybrids theoretically. Because of their known genetic constitution, hybrids were useful in homology assessment and ordering character states. The parental character set was generally robust, but some changes were made to reflect the special evidence offered by the hybrids. These hybrids suggest that the inclusion of hybrids in phylogenetic analysis will not lead to unresolved cladograms with rampant homoplasy, as has been predicted by other authors. Instead, the patterns of character inheritance in these hybrids lead to the prediction that a hybrid will be placed by phylogenetic analysis as a basal lineage to the clade that includes its most derived parent, with relatively little effect on homoplasy. These predictions will be evaluated by incorporation of the hybrids in phylogenetic analyses, to be reported in a subsequent paper.     

Hybrid breeding of rice via genomic selection

Hybrid breeding is the main strategy for improving productivity in many crops, especially in rice and maize. Genomic hybrid breeding is a technology that uses whole‐genome markers to predict future hybrids. Predicted superior hybrids are then field evaluated and released as new hybrid cultivars after their superior performances are confirmed. This will increase the opportunity of selecting true superior hybrids with minimum costs. Here, we used genomic best linear unbiased prediction to perform hybrid performance prediction using an existing rice population of 1495 hybrids. Replicated 10‐fold cross‐validations showed that the prediction abilities on ten agronomic traits ranged from 0.35 to 0.92. Using the 1495 rice hybrids as a training sample, we predicted six agronomic traits of 100 hybrids derived from half diallel crosses involving 21 parents that are different from the parents of the hybrids in the training sample. The prediction abilities were relatively high, varying from 0.54 (yield) to 0.92 (grain length). We concluded that the current population of 1495 hybrids can be used to predict hybrids from seemingly unrelated parents. Eventually, we used this training population to predict all potential hybrids of cytoplasm male sterile lines from 3000 rice varieties from the 3K Rice Genome Project. Using a breeding index combining 10 traits, we identified the top and bottom 200 predicted hybrids. SNP genotypes of the training population and parameters estimated from this training population are available for general uses and further validation in genomic hybrid prediction of all potential hybrids generated from all varieties of rice.     

The formation of the polyploid hybrids from different subfamily fish crossings and its evolutionary significance

This study provides genetic evidences at the chromosome, DNA content, DNA fragment and sequence, and morphological levels to support the successful establishment of the polyploid hybrids of red crucian carp x blunt snout bream, which belonged to a different subfamily of fish (Cyprininae subfamily and Cultrinae subfamily) in the catalog. We successfully obtained the sterile triploid hybrids and bisexual fertile tetraploid hybrids of red crucian carp (RCC) (female symbol) x blunt snout bream (BSB) (male symbol) as well as their pentaploid hybrids. The triploid hybrids possessed 124 chromosomes with two sets from RCC and one set from BSB; the tetraploid hybrids had 148 chromosomes with two sets from RCC and two sets from BSB. The females of tetraploid hybrids produced unreduced tetraploid eggs that were fertilized with the haploid sperm of BSB to generate pentaploid hybrids with 172 chromosomes with three sets from BSB and two sets from RCC. The ploidy levels of triploid, tetraploid, and pentaploid hybrids were confirmed by counting chromosomal number, forming chromosomal karyotype, and measuring DNA content and erythrocyte nuclear volume. The similar and different DNA fragments were PCR amplified and sequenced in triploid, tetraploid hybrids, and their parents, indicating their molecular genetic relationship and genetic markers. In addition, this study also presents results about the phenotypes and feeding habits of polyploid hybrids and discusses the formation mechanism of the polyploid hybrids. It is the first report on the formation of the triploid, tetraploid, and pentaploid hybrids by crossing parents with a different chromosome number in vertebrates. The formation of the polyploid hybrids is potentially interesting in both evolution and fish genetic breeding.     

Adaptation of the interspersed repetitive sequence polymerase chain reaction to the isolation of mouse DNA probes from somatic cell hybrids on a hamster background

A strategy for the rapid isolation of DNA probes from radiation-fusion Chinese hamster cell hybrids containing overlapping portions of the murine X chromosome based on the interspersed repetitive sequence polymerase chain reaction (IRS-PCR) previously used with human somatic cell hybrids has been developed. This specific amplification of mouse DNA on a hamster background depends on the use of primers directed to the B2 short interspersed repeat element family and the R repeat, from the long interspersed repeat element family, L1. Two sets of amplification conditions, which gave specific amplification of mouse DNA from either a mouse X-monochromosomal hybrid or irradiation-fusion hybrids having reduced X content, were defined. The mouse X-only chromosome hybrid yielded approximately 20 discrete reproducible bands, while the irradiation-fusion hybrids yielded between 1 and 10 discrete products. Comparison of different irradiation-fusion hybrids has allowed the definition of both specific and shared products corresponding to different regions within the overlapping X-chromosome fragments present within these hybrids. Use of such hybrids and the IRS-PCR technique has allowed the isolation of probes corresponding to the central region of the mouse X chromosome that contains the X-inactivation center. The method should be widely applicable to the isolation of mouse DNA sequences from mouse hybrid cell lines on either human or Chinese hamster backgrounds.     

Fitness of natural willow hybrids in a pioneer mosaic hybrid zone

Hybrid fitness is an important parameter to predict the evolutionary consequences of a hybridization event and to characterize hybrid zones. We studied fitness parameters of F₁ and later‐generation hybrids between the lowland species Salix purpurea and the alpine S. helvetica that have recently emerged during colonization of an alpine glacier forefield. Fruit production (number of capsules per catkin and fruit set) did not differ between hybrids and parents, but the number of seeds per capsule of F₁ hybrids was slightly lower than that of later‐generation hybrids and of the parents. Germination rates and seedling growth were tested on three substrates (pH 4.5, 7.0, and 8.0). Germination rates of seeds collected from F₁ hybrids were lower on acid and neutral substrates, but equal at pH 8.0 compared to all other groups, while the seeds from later‐generation hybrids performed as well as the parents on all three substrates. In seedling growth, the colonizer S. purpurea performed better than all other taxa on all three substrates, while hybrids resembled the subalpine species S. helvetica. Results suggest that endogenous selection acts against F₁ hybrids, but favors fitter genotypes in later‐generation hybrids. Exogenous selection via soil pH appears to be weak during seedling establishment. The pioneer vegetation on the glacier forefield may offer sufficient niche space for hybrid seedlings. Owing to the relatively high fitness of the hybrids and the scattered distribution of hybrids and parental individuals on the glacier forefield, this hybrid zone can be assigned to a mosaic model, probably facilitating gene flow and introgression between the parental species. As establishment of the hybrid zone appears to be linked to a colonization process, we propose to call it a pioneer mosaic hybrid zone.     

Characterization of somatic hybrids of potato by use of RAPD markers and isozyme analysis

Electrofusion of mesophyll protoplasts from two male sterile dihaploid Solanum tuberosum genotypes. DHAK-11 and DHAK-33, was performed. Selection of putative fusion products was based on vigorous callus growth. Regeneration of rooted putative hybrid plants was scored 14 weeks after fusion. Characterization of hybrids was performed by use of morphological assessment, random amplified polymorphic DNA (RAPD), and cytological and isozyme analysis. The rate of regenerated hybrids from callus was ca 6%. Of the putative hybrids, 45% were confirmed as true hybrids. Morphological assessment of the putative hybrids revealed that tetraploid and neartetraploid hybrids were vigorous plants with intermediate characteristics between the two parental phenotypes in respect to internode length, leaf size and shape, and purple pigmentation on the abaxial side of the leaves. Near-hexaploid hybrids were slender plants with small leaves and short petioles. Selected RAPD primers showed unique marker bands for the two parental genotypes. Hybrid plants revealed the unique marker bands from both parents. A total of 53 randomly chosen decamer primers were tested and 26 primers (49%) detected polymorphism between the two dihaploid parentals. Two primers revealed that one parental marker band was missing in two aneuploid hybrids. However, of 51 putative hybrids, a double test with two independently chosen primers showed unequivocally the hybrid character of 23 plants. The ploidy level of the hybrids was analysed by chromosome numbers in root tip cells and by number of guard cell chloroplasts. A strong correlation between the chromosome number and the number of chloroplasts was obtained. The hybrid nature of all RAPD-verified hybrids was confirmed by isozyme analysis with malate dehydrogenase.     

Entry of diphtheria toxin into cells: possible existence of cellular factor(s) for entry of diphtheria toxin into cells was studied in somatic cell hybrids and hybrid toxins

Ehrlich ascites tumor cells were found to be very insensitive to diphtheria toxin. We formed 37 hybrids from Ehrlich tumor cells and diphtheria toxin-sensitive human fibroblasts. The effects of diphtheria toxin on protein synthesis in those hybrids were examined. The hybrids were divided into three groups on the basis of toxin sensitivity. Group A hybrids were as sensitive to diphtheria toxin as human fibroblasts, Group C were as resistant as Ehrlich tumor cells, and Group B had intermediate sensitivity. Group A hybrids had diphtheria toxin-binding sites but Group B and C had no detectable binding sites. Elongation factor-2 of all the hybrids was susceptible to ADP-ribosylation by fragment A of diphtheria toxin. Cells of Group A and B became more sensitive to CRM 45 (cross-reacting material 45 of diphtheria toxin) after they were exposed to low pH (pH = 4.5). The resistance of Group C to CRM 45 was not affected by the same treatment. Group A and B hybrids and human fibroblasts had similar sensitivities to a hybrid toxin composed of wheat germ agglutinin and fragment A of diphtheria toxin, but Group C and Ehrlich tumor cells were resistant to this hybrid toxin. All the hybrids and Ehrlich tumor cells were more sensitive to a hybrid toxin composed of wheat germ agglutinin and subunit A of ricin than were human fibroblasts. On subcloning of Group B hybrids, one Group C hybrid was obtained, but no Group A hybrid. These facts suggest that Ehrlich ascites tumor cells differ from human fibroblasts in the expression of a factor(s) that is involved in entry of fragment A of diphtheria toxin into the cytoplasm after the toxin binds to its surface receptors.     

A Flow Cytometric Method for Rapid Selection of Novel Industrial Yeast Hybrids

We rapidly produced and isolated novel yeast hybrids by using two-color flow cytometric cell sorting. We labeled one parent strain with a fluorescent green stain and the other parent with a fluorescent orange stain, and hybrids were selected based on their dual orange and green fluorescence. When this technique was applied to the production of hybrids by traditional mating procedures, more than 96% of the isolates were hybrids. When it was applied to rare mating, three hybrids were identified among 50 isolates enriched from a population containing 2 × 10⁶ cells. This technology is not dependent on genetic markers and has applications in the development of improved industrial yeast strains.     

Electron microscope study of glial and fibroblast hybrid cells

The ultrastructure of a clone of rat glial cells, 3T3 mouse fibroblasts, and hybrids of these two cell types was compared. In the hybrids, morphological characteristics of glial cell are poorly expressed, whereas those of fibroblasts are strongly expressed. Microfibrils are seen in both parental lines. Microtubules and osmiophilic inclusions, which are frequently found in glial cells and are absent in fibroblasts, are quite rare in hybrids. By contrast, highly reticulated nucleoli, typical of fibroblasts, are prolific in hybrids. The lack of morphological expression of glial characteristics in hybrids is consistent with previous biochemical data on the expression of different functions in hybrids.     

三种普通欧洲鲤科鱼类(拟鲤、粗鳞鳊和欧鳊)人工杂交F1代形态学观察

对反交试验获得的18个月的拟鲤、粗鳞鳊和欧鳊F1代进行了鉴定.对不同于拟鲤、粗鳞鳊和欧鳊三种鱼的可量和可数形态特征分析表明,拟鲤×欧鳊和拟鲤×粗鳞鳊杂交种比粗鳞鳊×欧鳊杂交种与它们的双亲更容易区分.拟鲤杂交种间具有很多形态上的相似性,例如,上侧虹膜在拟鲤为红色,杂交种则介于双亲之间.在粗鳞鳊×欧鳊杂交种中也可以观察到居间类型.拟鲤×粗鳞鳊和拟鲤×欧鳊各自的杂交种可以通过眼睛的大小、较少的侧线鳞数和2行咽喉齿等特征相区分.粗鳞鳊×欧鳊杂交种与另外两个杂交种相比,具有更多的臀鳍分支鳍条数和一个中央具一黑线的虹斑.三个种进行杂交再获得的互交种通常不易区分.     

The products of gene A of the related phages Mu and D108 differ in their specificities

By recombination between different mutants of mutator phages Mu and D108, we isolated a set of viable hybrids. The structure of the hybrids was analyzed by digestion with different restriction enzymes. Genetic studies show that hybrids which carry the left end of the Mu genome complement a mini-Mu deleted from within the A gene as well as Mu while hybrids with the left end of the D108 genome or D108 do not. Vice versa, hybrids with the left end of the D108 genome or D108, but not hybrids with the left end of the Mu genome or Mu complement a mini-D108 deleted from within the A gene. The nucleotide sequence of the A gene of Mu and its equivalent on D108 are mainly similar except on their left end. These observations demonstrate that the two pA products, although only partially different, have different specificities.     

On the skeletal maturation of Japanese-American White hybrids.

The skeletal maturation of Japanese-American White hybrids is discussed in relation to that of Japanese and Whites. Assessment of skeletal maturation was made on 323 radiographs of 57 boys and 151 of 33 girls studied semi-longitudinally from 3 to 18 years on the basis of the Tanner-Whitehouse method (62). The skeletal maturity scores show a tendency for a greater advance in childhood for the Whites than for the hybrids and the Japanese. However, the preadolescent spurt of skeletal maturity occurs earlier in the Japanese and the hybrids than in the Whites, and the hybrids show the intermediate skeletal maturity scores between those of the Japanese and the Whites at and after adolescence.     

The Application of Fluorescence In Situ Hybridization in Different Ploidy Levels Cross-Breeding of Lily

21 crossing were conducted between Asiatic Lily with different ploidy levels, the results showed that the interploidy hybridization between diploid and tetraploid lilies was not as successful as intraploidy hybridization. Regardless of male sterility, triploid lilies could be used as female parents in the hybridization which the progenies were aneuploidy. 3x×4x crosses could be cultured more successfully than 3x×2x crosses. 45S rDNA was mapped on the chromosomes of seven Lilium species and their progenies using fluorescence in situ hybridization (FISH). FISH revealed six to sixteen 45S rDNA gene loci, and normally the sites were not in pairs. The asymmetry indexes of LA (Longiflorum hybrids × Asiatic hybrids) hybrids was higher than Asiatic hybrids, the evolution degree was LA hybrids > Asiatic hybrids. 45S rDNA distributed variably on chromosome 1-10 and 12 among Asiatic hybrids. Chromosome 1 had invariable sites of 45S rDNA in all Asiatic hybrids, which could be considered as the characteristic of Asiatic hybrids. LA hybrid ‘Freya’ had two sites of 45S rDNA on one homologous chromosome 5, and also it could be found in the progenies. The karyotype and fluorescence in situ hybridization with 45S rDNA as probe were applied to identify the different genotypes of 9 hybrids. Typical chromosomes with parental signal sites could be observed in all the genotypes of hybrids, it was confirmed that all the hybrids were true.     

Field efficacy of sweet corn hybrids expressing a Bacillus thuringiensis toxin for management of Ostrinia nubilalis (Lepidoptera: Crambidae) and Helicoverpa zea (Lepidoptera: Noctuidae)

Field studies were done in 1995-1996 to assess the efficacy of three sweet corn hybrids that express the Bacillus thuringiensis (Bt) toxin, CrylAb, against two lepidopteran pests, Ostrinia nubilalis (Hubner) and Helicoverpa zea (Boddie). The Bt hybrids tested were developed by Novartis Seeds, using the event BT-11, which expresses Bt toxin in green tissue as well as reproductive tissues including the tassel, silk, and kernel. Bt hybrids were compared with a standard non-Bt control or the non-Bt isoline for each hybrid; none of the hybrids were treated with insecticides during the study. Hybrid efficacy was based on larval control of each pest, as well as plant or ear damage associated with each pest. In both years, control of O. nubilalis larvae in primary ears of all Bt hybrids was 99-100% compared with the appropriate non-Bt check. Plant damage was also significantly reduced in all Bt hybrids. In 1996, control of H. zea in Bt hybrids ranged from 85 to 88% when compared with the appropriate non-Bt control. In 1996, a University of Minnesota experimental non-Bt hybrid (MN2 x MN3) performed as well as the Bt hybrids for control of O. nubilalis. Also, in 1996, two additional University of Minnesota experimental non-Bt hybrids (A684su X MN94 and MN2 X MN3) performed as well as Bt hybrids for percent marketable ears (ears with no damage or larvae). In addition, compared with the non-Bt hybrids, percent marketable ears were significantly higher for all Bt hybrids and in most cases ranged from 98 to 100%. By comparison, percent marketable ears for the non-Bt hybrids averaged 45.5 and 37.4% in 1995 and 1996, respectively. Results from the 2-yr study strongly suggest that Bt sweet corn hybrids will provide high levels of larval control for growers in both fresh and processing markets. Specifically, Bt sweet corn hybrids, in the absence of conventional insecticide use, provided excellent control of O. nubilalis, and very good control of H. zea. However, depending on location of specific production regions, and the associated insect pests of sweet corn in each area, some insecticide applications may still be necessary.     

Mechanistic analyses of site-specific degradation in DNA-RNA hybrids by prototypic DNA cleavers.

Bleomycin (BLM) binding and chemistry are apparently sensitive to differences in nucleic acid conformation and could conceivably be developed as a probe for sequence-dependent elements of conformation. We report on the development of a new methodology to synthesize heterogeneous DNA-RNA hybrids of defined sequence and present the results of our comparative studies on the cleavage of DNA and DNA-RNA hybrids by four drugs: BLM, neocarzinostatin and esperamicins A1 and C. In the case of BLM with duplex DNA, purine-pyrimidine steps such as GT and GC, are consistently hit, as previously observed. However, in heterogeneous sequence hybrids, not all GC sites are recognized by the drug, although all GT sites are. Suppressed GC sites are consistently flanked by pyrimidines on both the 3' and 5' sides, suggesting that the BLM binding site in hybrids spans at least four bases. Kinetic isotope studies with specifically deuterated substrates (kH/kD = 1.2-4.0) and the effect of oxygen on the product profile are presented in support of a mechanism consistent with 4'-hydrogen abstraction in hybrids. The powerful double-labeled probe technique was extended to study the mechanism of action of other DNA degrading drugs on DNA-RNA hybrids. For neocarzinostatin, the sequence specificity lies in the AT-rich region for hybrids and is similar to that of DNA, however, the overall cleavage pattern for the hybrid is significantly different from that for the same sequence of DNA. In the hybrid, a stretch of AT residues is essential and the A sites are damaged to a greater extent than they are in DNA. However, no kinetic isotope effects are observed and, based on the product profile, the mechanism of degradation of the DNA strand of hybrids seems to be limited to abstraction of the 5'-hydrogen. For esperamicin A1, damage on the DNA strand of hybrids occurs exclusively via 5'-hydrogen abstraction in a non-rate determining step and primarily at A and T sites. Esperamicin C behaves similarly, exhibiting no isotope effects at 1', 4' and 5' positions. Overall, the differences observed in site-specific cleavage between the two substrates is proposed to be a result of conformational differences between the DNA strand of duplex DNA and DNA-RNA hybrids.     

Phenotypes of cell hybrids formed by fusion of normal and Rous sarcoma virus transformed cells

Untransformed mouse cells were fused with rat cells transformed by a temperature sensitive mutant of avian sarcoma virus, and cell hybrids were isolated in the absence and in the presence of selective medium. None of the hybrids isolated were as transformed as the parent rat cells. All hybrids isolated in the absence of selective medium showed a phenotype similar to that of the untransformed mouse cell parent. Cell hybrids isolated on selective media, however, were more heterogenous. Some showed a phenotype that were intermediate between that of the two parental cells, while others were more like the untransformed mouse cells.     

Impact of plant resistance on southwestern corn borer (Lepidoptera: Crambidae) biology and plant damage

Southwestern corn borer, Diatraea grandiosella Dyar (Lepidoptera: Crambidae), is a major insect pest of corn, Zea mays L., in the southern United States. Germplasm lines with resistance to southwestern corn borer have been developed and released by the USDA-ARS. Two single-cross hybrids produced by crossing germplasm lines with resistance to southwestern corn borer and a susceptible single-cross hybrid were infested with southwestern corn borer larvae in a 2-yr field test conducted in Mississippi. The susceptible hybrid sustained significantly more leaf damage and stalk tunneling than either resistant hybrid. The number of tunnels and the length of tunneling were significantly lower on the resistant hybrids. In 2003, up to 15 times more tunneling was observed on the susceptible hybrid. Larvae feeding on the resistant hybrids were delayed in their movement from the whorl to the stalk and larval survival was 50% lower on the resistant hybrids than on the susceptible hybrid. Larvae recovered from the susceptible hybrid 7-14 d after infestation weighed twice as much as those recovered from the resistant hybrids. Similar differences in larval weight were observed in the laboratory when larvae were reared on diets prepared from lyophilized tissue from the three hybrids. These results provide a foundation for other investigations designed to identify and determine the roles of specific genes and gene families associated with southwestern corn borer resistance in corn.     

Sexually dichromatic hybrids between two monochromatic duck species,the Chiloé wigeon and the Philippine duck

Captive bird hybrids can provide important data on certain traits, such as hybrid viability and fertility. In this paper, we describe four hybrids between the Chiloé wigeon (Anas sibilatrix) and the Philippine duck (Anas luzonica). These two species diverged about 13 million years ago and are found on different continents, making the occurrence of wild hybrids extremely unlikely. Hence, these captive hybrids provide a unique opportunity to learn more about the outcome of hybridization between these highly divergent species. One pair of hybrids mated and produced six unfertilized eggs, suggesting that hybrids between these species are infertile. Morphologically, the hybrids were slightly larger than the parental species, but had intermediate bill lengths. With regard to plumage patterns, the hybrids displayed characteristics of both parental species: Males developed the iridescent green head pattern of the Chiloé wigeon, whereas the females showed the dark crown and eye stripe of the Philippine duck. Interestingly, Chiloé wigeon and Philippine duck are both sexually monochromatic whereas the hybrids showed clear sexual dimorphism. These hybrids can thus lead to novel insights into the genetic and developmental basis of sexual mono‐ and dichromatism in ducks.