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The genotyping‐by‐sequencing (GBS) approach was applied to genotype selected interspecific hybrid (F1) and backcross (BC2) families of Elaeis oleifera and Elaeis guineensis. Genome‐wide linkage disequilibrium (LD) was estimated at 150‐kb pairwise distance for r2 values of 0.17 and 0.42 for F1 and BC2, respectively. Single marker‐trait association analysis identified 47 markers associated with five fatty acid composition (FAC) traits (C16:0, C18:0, C18:1, C18:2 and iodine value [IV]) in F1, and 12 significant markers linked to oleic acid (C18:1) and vegetative traits (petiole width and mean leaf width) in BC. Within the QTL region associated with FAC traits, we identified key candidate genes influencing fatty acid synthesis. We implemented two machine learning algorithms, namely random forest and gradient boosting, to evaluate the ability of significant markers in predicting phenotype values. We also demonstrated the contribution of different marker combinations on trait values via prediction trees. This is the first attempt to evaluate the predictive ability of a combination of markers associated with traits identified from association mapping analysis in oil palm populations. [ABSTRACT FROM AUTHOR]

Summary: Allopolyploidization entailing the merger of two distinct genomes in a single hybrid organism, is an important process in plant evolution and a valuable tool in breeding programs. Newly established hybrids often experience massive genomic perturbations, including karyotype reshuffling and gene expression modifications. These phenomena may be asymmetric with respect to the two progenitors, with one of the parental genomes being "dominant." Such "genome dominance" can manifest in several ways, including biased homoeolog gene expression and expression level dominance. Here we employed a k‐mer–based approach to study gene expression in reciprocal Festuca pratensis Huds. × Lolium multiflorum Lam. allopolyploid grasses. Our study revealed significantly more genes where expression mimicked that of the Lolium parent compared with the Festuca parent. This genome dominance was heritable to successive generation and its direction was only slightly modified by environmental conditions and plant age. Our results suggest that Lolium genome dominance was at least partially caused by its more efficient trans‐acting gene expression regulatory factors. Unraveling the mechanisms responsible for propagation of parent‐specific traits in hybrid crops contributes to our understanding of allopolyploid genome evolution and opens a way to targeted breeding strategies. Significance Statement: Establishment of genome dominance is observed immediately after hybridization between plant species from two different genera using a novel RNA‐sequencing approach. This dominance is largely heritable, only marginally modified by cold stress and plant age and at least partly caused by more efficient trans‐acting regulatory factors of the dominant parent. Uncovering the nature and mechanisms of genome dominance contributes to the understanding of allopolyploid genome evolution and opens a way to targeted breeding strategies. [ABSTRACT FROM AUTHOR]

Maternal effects have been well documented for offspring morphology and life history traits in plants and terrestrial animals, yet little is known about maternal effects in corals. Further, few studies have explored maternal effects in gene expression. In a previous study, F1 interspecific hybrid and purebred larvae of the coral species Acropora tenuis and Acropora loripes were settled and exposed to ambient or elevated temperature and pCO2 conditions for 7 months. At this stage, the hybrid coral recruits from both ocean conditions exhibited strong maternal effects in several fitness traits. We conducted RNA‐sequencing on these corals and showed that gene expression of the hybrid Acropora also exhibited clear maternal effects. Only 40 genes were differentially expressed between hybrids and their maternal progenitor. In contrast, ~2000 differentially expressed genes were observed between hybrids and their paternal progenitors, and between the reciprocal F1 hybrids. These results indicate that maternal effects in coral gene expression can be long‐lasting. Unlike findings from most short‐term stress experiments in corals, no genes were differentially expressed in the hybrid nor purebred offspring after seven months of exposure to elevated temperature and pCO2 conditions. [ABSTRACT FROM AUTHOR]

Elderberry fruits are a good source of minerals and antioxidants; however, the presence of anti‐nutrients like oxalates may limit their utilization. The presented study which involves chemical evaluation of numerous interspecific hybrids is based on a hypothesis that interspecific genetic recombination may significantly improve the production and the nutritional quality of elderberry fruits. The aim of the first part of this study was to determine the oxalates (total, water‐soluble and insoluble) in fruits of 73 elderberry genotypes. In the second part, the dynamics of oxalate contents during fruit maturation was analysed. The average content of total oxalates in analysed genotypes was 721 ± 33 mg/100 g DW. The majority (91%, on average) were health harmless insoluble oxalates. The average content of total oxalates was increasing at the beginning of maturation and then it began to decrease significantly and reached its minimum value at full maturity, while the average of water‐soluble oxalates was gradually decreasing throughout maturation. Due to relatively high oxalate contents, some of the analysed hybrids should not be used for further breeding process. [ABSTRACT FROM AUTHOR]

Different flowering and closing times within a diurnal period play a significant role in reproductive isolation. However, few studies focused on the genetics of flower opening and closing times within a day for the lack of suitable plant materials. Iris dichotoma opens in the afternoon and closes in the evening, while I. domestica opens in the early morning and closes at dusk. Moreover, they have overlapping flowering phenology and produce fertile hybrids, providing an extraordinary opportunity to study the genetics of flower opening and closing times within a day. To illuminate the genetic mechanism regulating flower opening and closing times, the flowering processes of I. dichotoma (Y), I. domestica (S), and their hybrids: F1, F2, F1 × S, Y × F1, (F1 × S) × F1 and F1 × (F1 × S) were observed. The results indicated that flower opening and closing times are controlled by different polygenes. For flower opening time, opening in the early morning as I. domestica is partial dominant to opening in the afternoon as I. dichotoma. For flower closing time, flower closure at dusk is dominant to closure in the evening. [ABSTRACT FROM AUTHOR]

Abstract: The inheritance of mitochondrial DNA (mtDNA) in yeast hybrids is heteroplasmic, turning into homoplasmic after few cell cycles. Mitotype restoration is reported to be biparental and random. This study shows that mitotype restoration follows fixed schemata. We created isogenic, interspecific Saccharomyces cerevisiae × Saccharomyces uvarum hybrids through direct mating and analysed their mating frequency and mitotype. The mating frequency increased for most crosses in staggered mating. Mitotyping revealed that breeding lines with the same parental strain of S. cerevisiae and different parental strains of S. uvarum give rise to the same mitotype. According to our results, we postulate that the inheritance of mtDNA is dominated by one parental strain and that the superior mitotype is specific to each breeding line. Technological tests showed typical hybrid heterosis. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Hybrid zones are areas where gene flow between related species is currently occurring, so information on the compatibility between related species and their hybrids is essential for predicting the dynamics of such zones generated by introgressive hybridization. In this study, we quantified the compatibility among Magnolia stellata, M. salicifolia, and their hybrids in a hybrid zone using gene dispersal modeling. METHODS: After determining the genealogical classes of adult trees in the hybrid zone, the paternity of 574 open-pollinated seeds from 37 known maternal trees was analyzed with microsatellite markers. A neighborhood-based Bayesian gene dispersal model developed by us for estimating compatibility was then applied to the paternity data. KEY RESULTS: When M. stellata or M. salicifolia were mothers, interspecific mating to produce F1 hybrids yielded significant incompatibility, but backcrossing with F1 hybrids did not. Furthermore, when F1 hybrids became mothers, no significant incompatibility resulted from backcrossing to parental species or intra-F1 mating to produce F2 hybrids. The estimated proportion of F1 hybrids in the outcrossed seeds (1.7%) in the hybrid zone was much lower than that in the adult trees (14.0%). CONCLUSIONS: While it is difficult to obtain F1 hybrids, their low incompatibility makes it easy to produce advanced generation hybrids, once they have been successfully obtained. Although the production of F1 seeds is rare, heterosis and/or weak selection pressure in an empty niche between the parental species' niches may have contributed to the increased proportion of adult F1 hybrids in the hybrid zone. [ABSTRACT FROM AUTHOR]

Trifolium occidentale is a diploid wild relative with the potential to improve the drought and salt tolerances of white clover ( Trifolium repens). Previous work has shown that it is possible to efficiently produce large T. repens × T. occidentale breeding populations using colchicine-doubled (4×) T. occidentale. For effective introgression (backcross) breeding, it is also essential that interspecific chromosome pairing and recombination occur. In this study, it was apparent that chromosome pairing was occurring not only between T. occidentale and T. repens subgenomes, but also between the ancestral subgenomes of T. repens. Thus, interspecific hybridization has the potential for major genome recombination and opens the way for introgression of traits from T. occidentale into white clover. [ABSTRACT FROM AUTHOR]

Vulnerability to drought-induced cavitation is a key trait of plant water relations. Here, we summarize the available literature on vulnerability to drought-induced cavitation in poplars ( P opulus spp.), a genus of agronomic, ecological and scientific importance. Vulnerability curves and vulnerability parameters (including the water potential inducing 50% loss in hydraulic conductivity, P50) were collected from 37 studies published between 1991 and 2014, covering a range of 10 species and 12 interspecific hybrid crosses. Results of our meta-analysis confirm that poplars are among the most vulnerable woody species to drought-induced cavitation (mean P50 = −1.44 and −1.55 MPa across pure species and hybrids, respectively). Yet, significant variation occurs among species ( P50 range: 1.43 MPa) and among hybrid crosses ( P50 range: 1.12 MPa), within species and hybrid crosses (max. P50 range reported: 0.8 MPa) as well as in response to environmental factors including nitrogen fertilization, irradiance, temperature and drought (max. P50 range reported: 0.75 MPa). Potential implications and gaps in knowledge are discussed in the context of poplar cultivation, species adaptation and climate modifications. We suggest that poplars represent a valuable model for studies on drought-induced cavitation, especially to elucidate the genetic and molecular basis of cavitation resistance in Angiosperms. [ABSTRACT FROM AUTHOR]

Miscanthus × giganteus (Mxg) is an important bioenergy feedstock crop, however, genetic diversity among legacy cultivars may be severely constrained. Only one introduction from Japan to Denmark of this sterile, triploid, vegetatively propagated crop was recorded in the 1930s. We sought to determine if the Mxg cultivars in North America were all synonyms, and if they were derived from the European introduction. We used 64 nuclear and five chloroplast simple sequence repeat ( SSR) markers to estimate genetic similarity for 27 Mxg accessions from North America, and compared them with six accessions from Europe, including the species' type-specimen. A subset of accessions was also evaluated by restriction-site associated DNA sequencing ( RAD-seq). In addition, we assessed the potential of new crosses to increase Mxg genetic diversity by comparing eight new triploid Mxg progeny grown from seed, along with samples of the parental species M. sacchariflorus and M. sinensis. Estimates of genotyping error rates were essential for distinguishing between experimental error and true genotypic differences among accessions. Given differences in estimated error rates and costs per marker for SSRs and RAD-seq, the former is currently more cost-effective for determining if two accessions are genetically identical. We concluded that all of the Mxg legacy cultivars were derived via vegetative propagation from a single genet. In contrast with the Mxg legacy cultivars, genetic similarity to the type-specimen of eight new triploid Mxg progeny ranged from 0.46 to 0.56. Though genetic diversity among the Mxg legacy cultivars is critically low, new crosses can provide much-needed variation to growers. [ABSTRACT FROM AUTHOR]

Bighead carp ( Aristichthys nobilis) is an important aquaculture fish worldwide. Genetic linkage maps for the species were previously reported, but map resolution remained to be improved. In this study, a second-generation genetic linkage map was constructed for bighead carp through a pseudo-testcross strategy using interspecific hybrids between bighead carp and silver carp. Of the 754 microsatellites genotyped in two interspecific mapping families (with 77 progenies for each family), 659 markers were assigned to 24 linkage groups, which were equal to the chromosome numbers of the haploid genome. The consensus map spanned 1917.3 cM covering 92.8% of the estimated bighead carp genome with an average marker interval of 2.9 cM. The length of linkage groups ranged from 52.2 to 133.5 cM with an average of 79.9 cM. The number of markers per linkage group varied from 11 to 55 with an average of 27.5 per linkage group. Normality tests on interval distances of the map showed a non-normal marker distribution; however, significant correlation was found between the length of linkage group and the number of markers below the 0.01 significance level (two-tailed). The length of the female map was 1.12 times that of the male map, and the average recombination ratio of female to male was 1.10:1. Visual inspection showed that distorted markers gathered in some linkage groups and in certain regions of the male and female maps. This well-defined genetic linkage map will provide a basic framework for further genome mapping of quantitative traits, comparative mapping and marker-assisted breeding in bighead carp. [ABSTRACT FROM AUTHOR]

Background To increase rice production in Africa, considerable research has focused on creating interspecific hybrids between African ( Oryza glaberrima Steud.) and Asian ( O. sativa L.) rice in an attempt to obtain the positive attributes of each in new cultivars. Since flavor is a key criterion in consumer acceptance of rice, as an initial inquiry we characterized and compared the aroma chemistry of selected cultivars of African O. sativa ssp. japonica, O. sativa ssp. indica, O. glaberrima, and their interspecific hybrids grown in West Africa, using gas chromatography-mass spectrometry, gas chromatography-olfactometry and descriptive sensory analysis. Results Of 41 volatiles identified across seven representative rice cultivars grown in West Africa, 3,5,5-trimethyl-2-cyclopenten-1-one, styrene, eucalyptol, linalool, myrtenal and l- α-terpineol had not been previously reported in rice. Thirty-three odor-active compounds were characterized. 4-Ethylphenol and ( E, E)-2,4-heptadienal were unique to O. glaberrima, and pyridine, eucalyptol and myrtenal were described only in an interspecific hybrid. Descriptive sensory analysis indicated 'cooked grain', 'barny' and 'earthy' attributes were statistically different among the cultivars. Conclusion The aroma chemistry data suggest that it should be possible to separate African cultivars into distinct flavor types thereby facilitating selection of new cultivars with superior flavor in African rice breeding programs. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In the 1990s, an extraordinarily abundant live collection of the genus Pinus, including 49 species, 4 subspecies, and 7 interspecific hybrids, found in the Sochi Arboretum in Russia on the northeast coast of the Black Sea, was taxonomically revised. Among these taxa, two previously unknown interspecific hybrids of American hard pine species from P. sect. Trifoliae had arisen spontaneously in culture. These are described here as the new hybrid species Pinus × transamericana ( P. muricata × P. rigida) and Pinus × critchfieldii ( P. patula × P. taeda). All known natural or artificial interspecific hybrids within P. sect. Trifoliae are listed, and hybridization between American hard pine species is discussed. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Epichloid fungal endophytes ( Epichloë and Neotyphodium spp.) are excellent model systems for studying speciation processes because of their variable life history traits that are linked to host grass fitness. Presumed jumps to new hosts and subsequent somatic hybridizations appear to be common among epichloid endophytes resulting in increased genetic variation upon which selection can act and speciation be initiated. In this study, we explored the endophyte diversity of a rare European native woodland grass species, Hordelymus europaeus, along a latitudinal transect covering the entire distribution range of H. europaeus. From 28 populations in six countries, isolates were sampled and molecularly characterized. Based on the sequences of tubB and tefA, six distinct epichloid taxa (interspecific hybrid or cryptic haploid species) were found, of which four were novel and two have been previously reported from this host. Of the novel endophytes, two were presumed to be interspecific hybrids and two of nonhybrid origin. While previously known endophytes of H. europaeus are seed-born and strictly asexual, one of the novel nonhybrid endophytes found in the glacial refugium of the Apennine peninsula reproduced sexually in cultured plants. This is the first case of a seed-borne, but sexually reproducing endophyte of this host. We discuss the origin, and possible ancestral species, of the six epichloid taxa using phylogenetic analyses. Repeated host jumps and somatic hybridizations characterize the diversity of the endophytes. To date, no other grass species is known to host a larger diversity of endophytes than H. europaeus. [ABSTRACT FROM AUTHOR]

Androgenic dihaploids represent a unique form of dihaploids that have historically been utilized for cytoplasmic transfer, the generation of inbred lines and polyploid genome manipulations. Due to the apomictic nature of many Poa species, breeding improvements can be slow and difficult; therefore, alternative approaches that can capitalize on sampling the genetic diversity of near obligate Poa could be advantageous. This study investigates the frequency and potential use of androgenic derived dihaploids generated from a series of Poa arachnifera (Texas bluegrass) × Poa secunda (Sandberg bluegrass), Poa pratensis (Kentucky bluegrass) and Poa ligularis (Argentine bluegrass) interspecific hybrids. The examination of 2041 F1 hybrids generated from three interspecific hybridizations, confirmed the generation of 31 dihaploid individuals. Though low in occurrence, the generation of androgenic dihaploids derived through P. arachnifera interspecific hybridizations offers a non-traditional breeding approach for sampling genetic variability of Poa species and the development of new breeding resources. [ABSTRACT FROM AUTHOR]

There is no published evidence directly supporting the suggestion that long-spored isolates of Verticillium dahliae are interspecific hybrids. Retention in the nuclear genome of long-spored (amphihaploid) isolates of two sequence types where non-hybrid short-spored (haploid) isolates carry only single sequence types would provide such evidence. PCR amplicons for a partial β-tubulin gene and a 5 S rRNA-associated sequence were cloned and sequenced to provide multiple sequences for individual isolates. For the 5 S rRNA sequence, two sequence types were found for long-spored isolates, but only one for the haploid isolates. For the β-tubulin gene, two or three sequence types were found in long-spored isolates, but only one in most haploid isolates. One haploid isolate gave two sequence types, one like that from the other haploid isolates and the second like the short-sequence type from some long-spored isolates. These results support the long-spored isolates being interspecific hybrids between a ‘parental’ species similar to V. dahliae (haploid) and an unidentified second species. The presence of a sequence type in some long-spored isolates similar to that in one haploid isolate suggests a third ‘parental’ species may have been involved, possibly via a short-spored isolate that was itself hybrid. [ABSTRACT FROM AUTHOR]

1. Viviparous organisms vary greatly in their level of post-fertilization maternal provisioning and extensive provisioning (including very complex placentas) has evolved dozens of times in vertebrates. Through the use of species representing transitional states we aim to explore and develop empirically supported hypotheses that explain how such a complex trait has evolved. 2. In this study, we investigated the life histories and patterns of post-fertilization maternal provisioning in naturally occurring, all-female, hybrids between Poeciliopsis monacha, a viviparous species that produces large eggs and nourishes its embryos via stored yolk (lecithotrophy) and P. lucida, which produces small eggs and nourishes its embryos after fertilization via a follicular placenta (matrotrophy). Hybrids can be diploid or triploid, leading to different levels of gene dosage from the parental species. 3. We found that the extent of superfetation and average brood size of the hybrids did not differ significantly from their sexual parental species even though the latter was much lower in the hybrids. Moreover, the allodiploid, P. monacha-lucida, has intermediate sized eggs, whereas the allotriploid, P. monacha-monacha-lucida, produces eggs of similar size to those of P. monacha. The degree of post-fertilization maternal provisioning was unrelated to genomic dosages, with wild-caught hybrids being lecithotrophic, as seen in the maternal species ( P. monacha). 4. Our results with naturally occurring P. monacha-lucida hybrids differed from those obtained with laboratory-synthesized hybrid clones, which were either lecithotrophic or weakly matrotrophic. Consequently, we propose two non-mutually exclusive hypotheses to explain why lecithotrophic clones might be favoured in the wild. One hypothesis suggests that lecithotrophic hybrids minimize competition with the matrotrophic paternal sexual species from which they require sperm to reproduce. Alternatively, we propose that natural selection has eliminated matrotrophic hybrids that suffer from intergenomic conflict in the degree of post-fertilization maternal provisioning. 5. We have thus identified an empirical system and developed testable hypotheses that will help elucidate the selective pressures that caused the evolution of post-fertilization maternal provisioning and potentially provide an opportunity to explore how epigenetic factors (e.g., intergenomic conflict) might influence this complex trait. [ABSTRACT FROM AUTHOR]

Abstract: Several mutations are known to alter the normal progression of meiosis and can be correlated with defects in microtubule distribution. The dv mutation affects the spindle organization and chromosomes do not converge into focused poles. Two Brachiaria hybrids presented the phenotypic expressions of dv mutation but exhibited many more details in the second division. Bivalents were distantly positioned and spread over a large metaphase plate and failed to converge into focused poles. Depending on the distance of chromosomes at the poles, telophase I nuclei were elongated or the chromosomes were grouped into various micronuclei of different sizes in each cell. The first cytokinesis occurred. However, when there were micronuclei, a second cytokinesis immediately took place dividing the prophase II meiocytes into three or four cells. In each meiocyte, meiosis progressed to the second division. Slightly elongated nuclei or micronuclei were recorded in telophase II. After a third cytokinesis, hexads or octads were formed. Pollen grains of different sizes were generated. One of these hybrids presented a higher frequency of abnormal cells than when previously analyzed. The fate of these hybrids as genitors or as candidates for cultivars in the Brachiaria breeding program is discussed. [Copyright &y& Elsevier]

Endosperm balance number (EBN) was used to predict the outcome of crosses among a series of complex polyploid interspecific hybrids between Trifolium repens and T. nigrescens. Normal endosperm development, and hence seed-set, requires a 2 : 1 maternal : paternal EBN ratio in endosperm. Based on their crossability, T. repens (2 n = 4 x = 32) and T. nigrescens (2 n = 2 x = 16) were assigned the same EBN of 4. This number was used to predict the relative success of different backcrosses and intercrosses. The method was further developed to successfully predict which gametes would effect fertilization when complex polyploid hybrids with uneven genomic constitutions (5 x, 7 x) produced mixtures of euploid and aneuploid gametes. This was achieved by allocating EBNs to all potential gametes of complex polyploids. Allocation of gamete EBNs enabled not only prediction of the success or failure of a cross, but also which gametes would be filtered to effect fertilization in complex crosses. This enhanced ability to understand the potential outcomes of complex crosses will increase the efficiency of plant breeding programmes that integrate secondary gene-pools into economic species by interspecific hybridization. [ABSTRACT FROM AUTHOR]

Introduced Lolium species, including perennial ryegrass ( Lolium perenne) and Italian ryegrass ( Lolium multiflorum), have been widely utilized in Japan for forage, turf and soil conservation. These ryegrasses have escaped from cultivated areas and become naturalized, and this has become a serious issue in recent years. Interspecific hybrids between perennial ryegrass and Italian ryegrass have often been found in naturalized populations. It has also been suggested that hybridization between plant species might serve as a stimulus for the evolution of invasiveness. We surveyed the genetic structure of naturalized ryegrass populations in Japan using genetic markers that distinguished perennial ryegrass and Italian ryegrass. Of the 55 naturalized populations surveyed, 41 exhibited morphological traits of Italian ryegrass. DNA analysis using simple sequence repeat and chloroplast DNA markers characterized 20 of these 41 populations as Italian ryegrass, with the remaining populations as interspecific hybrid derivatives. Approximately half of the naturalized ryegrasses populations in Japan were inferred to include interspecific hybrids. [ABSTRACT FROM AUTHOR]

The aim of the present study was to produce Acipenser baeri× ( Huso huso× Acipenser ruthenus) hybrids in a diploid and triploid state and to study their viability in comparison with the A. baeri from the fish farm stock. A heat shock (37°C) in the 18th minute after fertilization was applied to induce triploidy. The survival rate and the ploidy level of the hybrids obtained were studied. The mortality of triploid hybrids was approximately twice as high as the mortality of diploid hybrids. No significant difference in the survival rate between Siberian sturgeon and their diploid hybrid with bester was noted. Cytogenetic analysis was performed by preparing chromosomes from the gill epithelium. The results showed that all studied fish from the heat-shocked group were triploid. [ABSTRACT FROM AUTHOR]

In the genus Oryza, interspecific hybrids are useful bridges for transferring the desired genes from wild species to cultivated rice ( Oryza sativa L.). In the present study, hybrids between O. sativa (AA genome) and three Chinese wild rices, namely O. rufipogon (AA genome), O. officinalis (CC genome), and O. meyeriana (GG genome), were produced. Agricultural traits of the F1 hybrids surveyed were intermediate between their parents and appreciably resembled wild rice parents. Except for the O. sativa× O. rufipogon hybrid, the other F1 hybrids were completely sterile. Genomic in situ hybridization (GISH) was used for hybrid verification. Wild rice genomic DNAs were used as probes and cultivated rice DNA was used as a block. With the exception of O. rufipogon chromosomes, this method distinguished the other two wild rice and cultivated rice chromosomes at the stage of mitotic metaphase with different blocking ratios. The results suggest that a more distant phylogenetic relationship exists between O. meyeriana and O. sativa and that O. rufipogon and O. sativa share a high degree of sequence homology. The average mitotic chromosome length of O. officinalis and O. meyeriana was 1.25-and 1.51-fold that of O. sativa, respectively. 4′,6′-Diamidino-2-phenylindole staining showed that the chromosomes of O. officinalis and O. meyeriana harbored more heterochromatin, suggesting that the C and G genomes were amplified with repetitive sequences compared with the A genome. Although chromocenters formed by chromatin compaction were detected with wild rice-specific signals corresponding to the C and G genomes in discrete domains of the F1 hybrid interphase nuclei, the size and number of O. meyeriana chromocenters were bigger and greater than those of O. officinalis. The present results provide an important understanding of the genomic relationships and a tool for the transfer of useful genes from three native wild rice species in China to cultivars. (Managing editor: Li-Hui Zhao) [ABSTRACT FROM AUTHOR]

Haploid and amphihaploid Verticillium dahliae isolates were studied using PCR-based molecular markers which: (i) discriminate the defoliating and nondefoliating pathotypes (two primer pairs INTD2f/r and INTND2f/r), and (ii) are species-specific (primer pair 19/22). The results were compared with some known biological and other molecular properties of the isolates. Five discrete sequences of the 19/22 amplicon were found. Sequence 4 was associated with both defoliating isolates from Spain and nondefoliating isolates from Spain and USA; these pathotypes were separated by the primer pairs INTD2f/r and INTND2f/r, but the data showed that the primer espdef01 (derived from the 19/22 amplicon) cannot be used for this purpose. Amplicon sizes and sequences with primers 19/22 divided amphihaploid isolates from crucifers (thought to be interspecific hybrids) into those corresponding to the previously reported α and β groups. The β-group isolates had either sequence 4 or 5 (these two differing by a single base). The distinct amplicon sequence 3 given by the α-group isolates demonstrated that the V. dahliae-like ‘parent’ of this group was molecularly unlike any haploid isolate yet studied. The overall results are discussed in relation to phytosanitary considerations and the probability of defoliating or crucifer pathotypes arising de novo within Europe, either by selection or by interspecific hybridizations. [ABSTRACT FROM AUTHOR]

Changes in host acceptance is an important factor in the host specialization of phytophagous insects, and knowledge of the genetic organization of this behaviour is necessary in order to understand how host shifts occur. Here we describe the inheritance of adult host acceptance (oviposition) in three closely related species ofYponomeutaLatreille (Lepidoptera: Yponomeutidae), and their interspecific hybrids.Yponomeuta cagnagellus(Hübner), a specialist onEuonymus europaeusL. (Celastraceae),Y. malinellusZeller, a specialist onMalusspp. (Rosaceae), andY. padellus(L.), oligophagous on a number of Rosaceae, were tested for their acceptance of parental hosts in choice tests. Acceptance ofE. europaeusis semi-dominant in hybrids ofY. cagnagellus× Y. padellus, and in hybrids ofY. cagnagellus× Y. malinellus. The dominance of this acceptance was confirmed in oviposition tests with backcross hybrids: backcross hybrids F1×  Y. cagnagellusoviposited mainly onE. europaeusand F1×  Y. padellusstill deposited more than half of their egg masses onE. europaeus. Reciprocal hybrids did not differ in their host acceptance, indicating that the trait is autosomal. We further studied the effect of larval food on adult host acceptance (‘Hopkins host selection principle’) in split full-sib F1 families. Larval diet influenced oviposition only in one of two hybrid crosses. The F1 hybrid ofY. padellus×  Y. cagnagellus, reared onPrunus spinosaL., deposited a significantly lower percentage of egg masses onE. europaeuscompared to their full-sib sisters fed withE. europaeus. We did not find this in the reciprocal cross. However, still more than half of the egg masses are deposited onE. europaeusby hybrids that have no experience on this host. We conclude that the semi-dominant character of acceptance ofE. europaeusand a tendency of Rosaceae-feedingYponomeutato deposit egg masses on this host may have created the opportunity for the host shift of the predecessor ofY. cagnagellusfrom Rosaceae to the Celastraceae. This shift may have been further facilitated by a weak tendency of adults to oviposit on their larval food source. [ABSTRACT FROM AUTHOR]

Arachis kempff-mercadoiis a wild species from the sectionArachis. Allkempff-mercadoiaccessions originate from the Santa Cruz province of Bolivia and they representArachisspecies with the A genome. From molecular analysis it was found that although cultivatedA. hypogaeais made up of A and B genomes,A. kempff-mercadoimay not be as closely related to it as are some of the other A genome species.Arachis kempff-mercadoiis of interest because it has multiple disease resistance. It was crossed with a SpanishA. hypogaeacultivar which is susceptible to foliar diseases and to the insect pestSpodoptera litura. The success rate of the crossA. hypogaea(2n = 40) × A. kempff-mercadoi(2n = 20) was very low, but it could be increased by culturing immature seedsin vitro. Although the hybrids were triploids, a few fertile pollen grains were obtained due to the formation of restitution nuclei in the F1 plants. Interspecific derivatives at the BC2F2 generation were scored for early leaf spot, late leaf spot and toSpodopteradamage. Screening results showed that 29% of the derivatives had both early and late leaf spot resistance and that less than 5% of the derivatives had resistance to both the foliar diseases and toSpodoptera. [ABSTRACT FROM AUTHOR]

Epichloë endophytes are fungal symbionts of grasses that span a continuum including asexual mutualists that are vertically transmitted, obligately sexual pathogens that are horizontally transmitted, and mixed-strategy symbionts with both mutualistic and pathogenic capabilities. Here we show that processes of genome evolution differ markedly for the different symbiont types. Genetic and phylogenetic analysis was conducted of a broad taxonomic, ecological and geographical sample of sexual and asexual isolates, in which were identified and sequenced alleles of genes for Β-tubulin ( tub2 ) and translation elongation factor 1-α (tef1), and microsatellite alleles were identified by length polymorphisms. The majority of asexual isolates had two or three alleles of most loci, but every sexual isolate had only single alleles for each locus. Phylogenetic analysis of tub2 and tef1 indicated that in all instances of multiple alleles in an isolate, the alleles were derived from different sexual species. It is concluded that, whereas horizontally transmissible species had haploid genomes and speciation occurred cladistically, most of the strictly seedborne mutualists were interspecific hybrids with heteroploid (aneuploid or polyploid) genomes. Furthermore, the phylogenetic evidence indicated that, in at least some instances, hybridization followed rather than caused evolution of the strictly seedborne habit. Therefore, the abundance of hybrid species among grass endophytes, and their prevalence in many host populations suggests a selective advantage of hybridization for the mutualistic endophytes. [ABSTRACT FROM AUTHOR]

Interspecific hybrids between white clover ( Trifolium repens L.) and Caucasian clover ( Trifolium ambiguum M. Bieb.) have been developed to introgress the rhizomatous growth habit into white clover, to increase persistence and drought tolerance. The forage quality of T. repens, T. ambiguum and the backcross 1 (BC1) and backcross 2 (BC2) hybrids and companion grass, when grown in mixtures with an intermediate perennial ryegrass ( Lolium perenne L.) under a cutting-only management, was measured. In vitro dry-matter digestibility (DMD), water-soluble carbohydrate (WSC) and crude protein (CP) concentrations of the legume and grass fractions were measured throughout the growing season over three harvest years. Trifolium repens had a lower WSC but a higher CP concentration than the perennial ryegrass companion in all harvest years and at all cuts. The legume fractions from the BC1 and BC2 hybrid plots had a higher WSC and a lower CP concentration but an in vitro DMD value comparable with white clover throughout the growing season and in each harvest year. The grass fractions from the mixtures with the backcross hybrids had a higher WSC and a lower CP concentration than the grass fraction from the T. repens plots, in all harvest years and throughout the growing season. No difference in in vitro DMD between parental species and backcross hybrids was observed. The implications of these results for the development of these hybrids and animal performance are discussed. [ABSTRACT FROM AUTHOR]

Abstract The dry matter (DM) production of Trifolium repens , T. ambiguum and the backcross 1 (BC1) and backcross 2 (BC2) hybrids with T. repens as the recurrent parent were compared in mixtures with an intermediate heading variety of perennial ryegrass (Lolium perenne L.) under a cutting-only management over 3 harvest years. Plots of parental legume species and backcross hybrids were established from small plantlets and oversown with the companion grass. In the first harvest year, the DM yield of clover in T. repens plots was greater than that in the BC2 plots and both greater than in the BC1 plots, whilst in the second and third harvest years differences between the DM yield of clover in the T. repens and the BC1 and BC2 hybrid plots were small. Similar results were obtained for the DM yield of total herbage. There were also differences in seasonal growth in the first harvest year, when yield of clover in T. repens plots was greater than in the BC1 and BC2 hybrid plots at early cuts but not at later cuts. Few differences in seasonal growth were observed between parental species and hybrids in subsequent harvest years. Comparison of above- and below-ground biomass showed more DM in roots and rhizome of clover in the backcrosses than in the T. repens plots in the second harvest year but differences were less evident in the third harvest year. The clover in the backcross hybrid plots also had fewer stolon growing points per quadrat than the T. repens plots, but the BC2 had more than the BC1 plots. The exploitation of these hybrids in breeding programmes as a strategy to improve the persistence and drought tolerance of white clover is discussed and implications for forage production considered. [ABSTRACT FROM AUTHOR]

Backcross hybrids between the important forage legume white clover Trifolium repens, which is stoloniferous, and the related rhizomatous species T. ambiguum have been produced using T. repens as the recurrent parent. The drought tolerance of parents and two generations of backcross plants, possessing both stolons and rhizomes, was studied in deep soil bins in a glasshouse both as monocultures and in mixtures with perennial ryegrass. Soil moisture content, leaf relative water content, and leaf water potential were measured on plants subjected to drought cycles of 4 weeks duration and those watered normally and maintained at field capacity. Six cycles of drought, carried out over 2 years, showed that T. ambiguum and the first and second generation backcross hybrids maintained a greater leaf relative water content and higher leaf water potential than T. repens at comparable levels of soil moisture. The dry matter yield of T. repens was significantly reduced over each drought cycle compared to the watered treatments, while the yield of T. ambiguum increased over the 4-week cycle in both treatments. The yield of the backcross generations was intermediate between those of the two parental species. The implications of these results for white clover germplasm improvement programmes are discussed. [ABSTRACT FROM AUTHOR]

Abstract Hybrids between white clover (Trifolium repens L.) and Caucasian clover (or Kura clover, Trifolium ambiguum M. Bieb) are a potential route for the improvement of drought tolerance and persistence in white clover. However, to be agronomically viable they must show no significant reduction in their potential for nitrogen fixation relative to white clover. A comparative study of growth rate and nitrogen fixation was carried out in flowing solution culture without a supply of mineral nitrogen to the plants. The two parental species and two generations of backcross hybrids, with white clover as the recurrent parent, were assessed. The growth rate and N content of T. ambiguum were significantly lower than those of the other lines. However, dry matter production, nodule biomass per plant and rates of fixation were similar in second-generation backcross plants and white clover. The results suggest that the agronomic potential of this novel germplasm is not compromised by limitations with respect to nitrogen fixation. [ABSTRACT FROM AUTHOR]

A combination of genomic in situ hybridization (GISH) and meiotic pairing analysis of crosses between a series of 2n = 56 partial amphiploids confirmed that the alien genome of the BYDV-immune Agrotricum line OK7211542 is derived from Thinopyrum ponticum and not from Thinopyrum intermedium. The evidence from meiotic paring analysis indicated that the chromosome constitution of OK7211542 is similar to other Agrotricum line, ORRPX, which was derived from a cross of wheat and Th. ponticum, but different from other Agrotricum lines, Zhong 5 and TAF 46 which were derived from the crosses between wheat and Th. intermedium. The GISH analysis confirmed that OK721152 containen done complete set of 14 Th. Ponticum chromosome, in which no S chromosome was present in the alien genome. GISH also detected a small alien translocation attached to one of the wheat chromosomes, a result that was consistent with the pairing data. [ABSTRACT FROM AUTHOR]

Ovary slice culture, after cut-style pollination, was used to develop interspecific hybrids between Lilium longiflorum and L. concolor. Reciprocal crosses between diploid cultivars (2n = 2x = 24) were carried out. On the days 30, 35, 40 and 45th after pollination (DAP), ovaries were sliced and cultured on a modified hormone-free Murashige-Skoog (M-S) medium without NH4NO3, supplemented with 6% sucrose, 50 mg/l yeast extract and 0.25% gelrite at pH 6.3. For the L. longiflorum × L. concolor cross, ovule germination was found to be best at 30 DAP. After transfer to a M-S (half-strength) medium supplemented with 1.5% sucrose and 0.25% gelrite at pH 5.8, diploid and triploid hybrid plants were established. In contrast, ovules from the L. concolor × L. longiflorum cross did not germinate. The hybridity of the plantlets obtained was verified by karyotype and isozyme analysis. The importance of the ovary slice culture technique as a tool to develop new hybrids between incompatible lilly plants is discussed. [ABSTRACT FROM AUTHOR]

Resistance responses of resynthesized Brassica napus lines to infection with Plasmodiophora brassicae were investigated. Lines that were derived from interspecific crosses between clubroot-resistant B. rapa and resistant B. oleracea exhibited very broad and effective resistance in both greenhouse and field tests. When clubroot resistance was introduced into resynthesized lines from the B. oleracea parent only, the plants were mainly susceptible. Interspecific hybrids from the most resistant parental genotypes. i e. B. campestris ECD-04 and the B. oleracea cultivars ECD-15 or 'Böhmerwaldkohl', were used to initiate a B. napus resistance-breeding programme. These artificial rapeseed lines were resistant to isolates that were virulent on all B. napus differential lines and/or parental lines Preliminary segregation analysis suggests that their resistance is due to at least two dominant and unlinked genes. In some cases progenies from selfed resynthesized plants exhibited resistance reactions that differed from those of the parental hybrid plant; this may have been the result of cytological instability. [ABSTRACT FROM AUTHOR]

The objectives of this research were to gather hybridization information about crosses between tetraploid and synthetically derived octoploid lines of Avena and their reciprocals, and to study the cytology of the hybrids obtained. When the octoploid plants were used as females, only 2.6% of the pollinated florets set seed, while seed set increased to 39.0% in reciprocal crosses. However, germination was 95.7% for the first group of hybrids and only 18.2% for the reciprocals. These diverse results can be explained by the paternal : maternal endosperm genomic ratios and the hypothesis of polar nuclei activation. The tetraploid-octoploid hybrids did not always contain 42 chromosomes. Octoploid lines derived indirectly from tetraploid (AABB) × hexaploid (AACCDD) crosses were found to retain their A and B genome chromosomes. Univalents in the above hybrids averaged 15.44 in 1990 and 15.15 in 1991, indicating the presence of C and D genome chromosomes inherited from the octoploid lines. Directly synthesized octoploids from diploid (AcAc) × hexaploid (AACCDD) crosses were found to form 20.44 univalents, 5.30 bivalents, and 2.69 trivalents when crossed with AABB tetraploid species. The high number of univalents indicates that chromosomes from at least three genomes, i.e. B, C, and D, remain unpaired, while trivalents are the result of homology between the A and Ac genomes. Hybrids between tetraploid and octoploid lines can be obtained at low frequencies but, regardless of the direction of the cross, these hybrids are highly sterile. [ABSTRACT FROM AUTHOR]

To gain more information about the widely unknown genome constitution of the taxonomically and agronomically interesting wild oat Avena macrostachya, this tetraploid species was crossed (as the pollinator) with several diploid Avena species. Hybridization failed with A. strigosa (As s), A. hirtula (As As), and A. longiglumis (A1 A1), but succeeded with A. atlantica (s As), A. prostrata (Ap Ap), and A. pilosa (Cp Cs). The output of hybrids and the vitality of the F1 plants were highest in the combination A. pilosa × A. macrostachya. Hybrids from this cross relatively frequently showed trivalents at metaphase I as compared to the nearly consistent formation of seven univalents and seven bivalents in hybrids with the A genome species A. atlantica and A. prostrata. Altogether, the results confirm an autoploid origin of A. macrostachya and demonstrate that among the two known basic genomes A and C of the genus Avena only the latter exhibits considerable homeology to the A. macrostachya genome. [ABSTRACT FROM AUTHOR]

Anther culture has been demonstrated to be an applicable technique for the development of doubled haploid, i. e. homozygous lines of many crop species. In some species, androgenetic doubled haploids have already been shown to be a useful tool for breeding. However, anther culture results in sunflower have been rather unsatisfactory up to now. As in other species, anther culture response of sunflower (Helianthus sp.) is strongly affected by physical, nutritional, physiological and genetical factors. By testing a number of different culture parameters, i. e. donor plant stages, culture media and conditions, and appropriate schedule could be worked out for the successful regeneration of shoots -- at least for a number of sunflower lines and interspecific hybrids. [ABSTRACT FROM AUTHOR]

Allied species of crop Brassicas have potential value as donors of useful nuclear/organelle genomes. Eruca sativa, a member of subtribe Brassicineae, is resistant to white rust and well adapted to drought. Attempts to hybridize it with Brassica campestris by conventional methods were unsuccessful. However, hybrids were obtained by embryo rescue and the hybrid embryos were found to produce numerous secondary embryos in upto 7 to 8 subcultures. Plantlets developed from them exhibited morphological characteristics of both parents. The chromosome number of 2n = 42 showed that they were amphidiploids. The plants were allotetraploids (2n = 42) and showed 21 bivalents at M1 of meiosis. Hybridization of total DNA of the hybrids with two probes, a B. campestris tandem repeat DNA and 18s ribosomal DNA of wheat showed that it was derived from the genome of both parents. The hybrids are self-fertile and show the same high fertility even in A3 generation. They were selfed or crossed with B. juncea, B. campestris and B. nigra to screen for useful agronomical traits. Six more embryos of E. sativa x B. campestris have been obtained and their growth is being studied. Preliminary small scale field trials indicate that the selfed hybrid is comparable in yield with a high yielding commercial variety of B. juncea. [ABSTRACT FROM AUTHOR]

The meiotic behaviour of the hybrid between Festuca gigantea (2n - 6x = 42) and Festuca arundinacea (2n = 6x = 42) indicates distinct structural differences between the two species. These differences are also apparent in the degree of chromosome pairing observed in Lolium multiflorum × F. gigantea compared with previous reports on the L. multiflorum × F. arundinacea hybrids. Although the L. multiflorum × F. gigantea 8x amphiploid combines the complementary characters of the two species and is agronomically interesting, there are some irregularities in meiotic behaviour that could affect the stability of the amphiploid. Seed fertility in the amphiploid is high and preliminary studies show evidence of a high degree of self-fertility. The pentaploid hybrid between autotetraploic L. multiflorum × F. gigantea is sufficiently fertile to be used as the pollen plant in crosses with diploid L. multiflorum (BC[Sub1]. Backcrossing the BC[Sub1] hybrid to L. multiflorum results in mainly diploid progeny. The possibilities of using this crossing scheme to introgress F. gigantea characters into L. multiflorum is discussed as an alternative approach to amphiploid breeding as a means of combining specific complementary characters of the two species. [ABSTRACT FROM AUTHOR]

The performance of single cross hybrid between resynthesized (resyn) genotypes and varieties of rapeseed was tested in microplots. The results revealed strong genetic differences between the artificially synthesized rapeseed forms for all the characters investigated, as well as for g.c.a. values. In particular, hybrids with resyn rapeseed exhibited a vigorous vegetative growth. It should, therefore, be beneficial to use resyn forms directly in fodder rape breeding programmes. Disturbances in fertility of the resyn material resulted in a low number of seeds per pod and consequently in an inferior seed yield as compared to the varieties, although some high yielding combinations were also identified. Three-way hybrids with a 25 % genome share of the resyn rapeseed reached only lower vegetative performance as compared to the hybrids with a 50 % resyn genome but their performance in generative trait was generally superior. In respect to seed yield some progenies of three-way hybrids showed a higher plot performance than, even the highly yielding varieties. A further comparison between single-cross combinations of resyn × variety on the one hand and variety × variety on the other hand demonstrated that resyn genotypes, due to a distinct apical dominance, exhibited a pronounced expression of characters measured en the main stem. But in total, it is evident from the present findings that any hybridization with this resyn material does not promise immediate short- term varietal improvement. [ABSTRACT FROM AUTHOR]

Three genotypes of Avena sativa L, were crossed to A. magna Murph, et Terrell, From the sterile pentaploid F[SUB1] amphiploids were successfully developed after colchicine treatment. The C[SUB1] plants were observed for their morphology, cytology and tertiliry. These plants were characterized by longer and broader glumes, swollen pedicel attachment, pubescent lemmas, bold seeds and persistent spikelets. Other characters, viz., final plant height, rachis length, peduncle length and spikelets per panicle were intermediate. All plants had the chromosome number 2n = 70 or close to 70. Due to stickiness of chromosomes, meiosis of only two decaploid plants could be studied in detail. The average chromosome association was 1.3 I + 28.56 II + 1.4 III + 1.77 IV + 0.07 VI and 0.13 I + 28.7 II + 0.14 III + 2.09 IV + 0.59 VI; but in some cells up to 35 bivalents were observed. Seed set as well as pollen fertility and size exhibited great variation. [ABSTRACT FROM AUTHOR]

Ten microsatellite markers have been isolated from an amphihaploid isolate of Verticillium dahliae using genomic libraries enriched for (AGT), (GAC), (GCC), (TAC) and (TTA) repetitive elements. These were characterized on four amphihaploid isolates and two haploid isolates each of V. dahliae and Verticillium albo-atrum. Nine were polymorphic, with between two and five alleles, and the tenth was polymorphic when tested on a further 20 haploid V. dahliae isolates (three alleles). Only one primer pair gave the expected double bands from the amphihaploid isolates, supporting the view that V. albo-atrum is not one of the parents of the interspecific hybrid amphihaploid isolates. [ABSTRACT FROM AUTHOR]

Abstract The Libusta (Coffea canephora P. × C. liberica B.) programme initiated in the seventies in Côte d'Ivoire aims at improving the quality of coffee grown in low altitudes, with a yield comparable to current commercial C. canephora clones. The second generation of back-crosses to the C. canephora (CAN) parent, BC2, are now likely to be commercially exploited as far as yield is concerned. The best BC2 progeny yielded 1386 kg of green coffee/ha/y, averaged over five harvest years. On average, the genetic gain for yield from BC1 to BC2 reached 22%. In a factorial mating design, no interaction was observed between BC1 and CAN parents, while both main effects were highly significant. This explained that observed genetic gains and further genetic gains may be achieved with appropriate strategies. [ABSTRACT FROM AUTHOR]

AbstractRandom amplified polymorphic DNA (RAPD) markers were used to verify interspecific hybridization in Alstroemeria. Five putative interspecific hybrids and their parents were analysed by means of four preselected RAPD primers. The putative parentage was confirmed in four hybrids and was excluded in one that showed completely different RAPD patterns from its putative parents and a different phenotype. Our results demonstrated that this molecular technique is a powerful tool for verifying hybridity rapidly if the putative parents are given. This tool will allow screening of small immature seedlings for verification of hybridity and should improve the efficiency of breeding programmes. [ABSTRACT FROM AUTHOR]

Hybnds between the stoloniferous Trifolium repens (2n = 4x = 32) and the rhizomatous Trifolium ambzguunz (2n = 4x = 32) have been produced using T. repens as the recurrent parent. Morphological characteristics of the parent species and the F[sub1], BC1, BC2 and BC3 hybrids were examined in a glasshouse experiment. Leaflet ratios and general plant shape indicated that the BC3 hybrid was similar to T repens. Separation of plants into components of above- and below-ground growth showed that T. repens had a greater total plant dry weight than T. ambiguum but 24% of its dry weight was in roots compared with 22% in roots and 44% in rhizomes in T. ambiguum. The BC3 generation contained plants that were predominantly T. repens-like with stolons, but also had a small proportion of their total dry weight (3%) as rhizome, confirming the potential to produce plants that combine stoloniferous and rhizomatous growth. The proportions of rhizome and stolon varied within the BC3 generation, enabling further selection and plant breeding. The BC3 hybrids produced similar numbers of inflorescences to T. repens however, fertility was lower, although there was some variation within the BC3 for both characters. [ABSTRACT FROM AUTHOR]

Eleven interspecific hybrids of cassava with the wild relatives Manihot glaziovii, M. pseudoglaziovii. M. dichotoma and M. anomala were examined to detect unreduced microspores. The frequency of dyads and triads was counted, as well as pollen viability. Of these hybrids, the second generation progeny of cassava×M. glaziovii showed a high frequency of unreduced microspores (3.7%) permitting their selection for further manipulation of this character. An association of vegetatively- reproduced genotypes and the occurrence of unreduced microspores has also been observed. [ABSTRACT FROM AUTHOR]

The objective of this study was to establish genomic relationships among G. soja, G. max, and G. gracilis' based on cytogenetic analyses. All three species hybridized readily, though pod set was low (2.2 %-5.3 %); seeds produced viable, vigorous and totally fertile F1 plants which were normal in meiotic pairing. This suggests that all three species belong to one gene pool and should be considered as forms of one species. [ABSTRACT FROM AUTHOR]

Self-sterile interspecific hybrids between diploid Lolium perenne and either Festuca arundinacea or F. gigantea (both hexaploids) set some seeds when subjected to a heavy pollen cloud from the amphiploids derived from the hybrids. All the progeny were octoploid and were formed from the fertilization of unreduced gametes in the F[SUB1] hybrid by amphiploid pollen. The significance of the results in relation to breeding efforts within the Lolium/Festuca complex is discussed. [ABSTRACT FROM AUTHOR]

Abstract Damage caused by the eucalypt snout weevil Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae) (= G. gibberus Boisduval) was found on a greater proportion of F1 Eucalyptus amygdalina Labill. × E. risdonii J. D. Hook. hybrid trees than either of the pure species, in a replicated field trial in south-east Tasmania. A greater proportion of E. risdonii trees was also damaged than E. amygdalina trees. A study of the pattern of oviposition within the trial revealed no difference in oviposition by G. scutellatus between E. risdonii and E. amygdalina . Oviposition by G. scutellatus was significantly higher on the F1 and F2 interspecific hybrids between these two eucalypt species compared with pure species crosses. There were no apparent differences in damage or oviposition levels between the F1 hybrids and the single large F2 progeny included in the trial. This finding provides little evidence that hybrid susceptibility is due to hybrid breakdown after the first generation. Rather, the evidence is consistent with the hypothesis that there may be different mechanisms of host defence operating in each species that are somehow diluted below a threshold level in the hybrids. [ABSTRACT FROM AUTHOR]

The sucrose content of coffee bean is an important component of the coffee flavour: the higher the sucrose content in green beans, the more intense coffee cup flavour. Beans of the anciently cultivated cultivar Coffea liberica ‘dewevrei’ have low levels of sucrose compared with beans of the wild species Coffea pseudozanguebariae. In the present study, the inheritance of the sucrose accumulation in the interspecific cross C. pseudozanguebariae × C. liberica ‘dewevrei’ was examined. The sucrose content was measured in mature beans of both parental species, and in F1 and backcross hybrids using high-pressure liquid chromatography coupled to pulsed amperometric detection. The sucrose accumulation in all but one hybrid, showed genetic additivity. A segregation distortion was identified in the offspring of the backcross to C. pseudozanguebariae. There was no year effect and only a low genotype × year interaction. Consequences for breeding, in relation to the coffee cup taste improvement, are discussed. [ABSTRACT FROM AUTHOR]