Cytogenetic characterization of Solanum lycopersicoides Dun. alien chromosome additions in cultivated tomato

Cytogenetic analysis of five Solanum lycopersicoides monosomic alien addition lines of tomato was carried out. Meiotic analysis showed that additional chromosomes caused serious abnormalities. It was demonstrated that different chromosomes of S. lycopersicoides had different effects on chromosome pairing. For instance, associations formed between chromosomes II and IV of S. lycopersicoides and chromosomes of cultured tomato were trivalents, while chromosome XI in all cells was present as a univalent. Pachytene analysis showed that chromosomes of homeologous group II paired at their long arms, and their nucleolus organizer regions were of different sizes. The use of molecular markers provided accelerated identification of the introgression of S. lyvcopersicoides genetic material.     

Ecological genetics of invasive alien species

There is growing realisation that integrating genetics and ecology is critical in the context of biological invasions, since the two are explicitly linked. So far, the focus of ecological genetics of invasive alien species (IAS) has been on determining the sources and routes of invasions, and the genetic make-up of founding populations, which is critical for defining and testing ecological and evolutionary hypotheses. However an ecological genetics approach can be extended to investigate questions about invasion success and impacts on native, recipient species. Here, we discuss recent progress in the field, provide overviews of recent methodological advances, and highlight areas that we believe are of particular interest for future research. First, we discuss the main insights from studies that have inferred source populations and invasion routes using molecular genetic data, with particular focus on the role of genetic diversity, adaptation and admixture in invasion success. Second, we consider how genetic tools can lead to a better understanding of patterns of dispersal, which is critical to predicting the spread of invasive species, and how studying invasions can shed light on the evolution of dispersal. Finally, we explore the potential for combining molecular genetic data and ecological network modelling to investigate community interactions such as those between predator and prey, and host and parasite. We conclude that invasions are excellent model systems for understanding the role of natural selection in shaping phenotypes and that an ecological genetics approach offers great potential for addressing fundamental questions in invasion biology.     

Production and characterization of alien chromosome additions in shallot (Allium cepa L. Aggregatum group) carrying extra chromosome(s) of Japanese bunching onion (A. fistulosum L.)

First and second backcrosses of amphidiploid hybrids (2n = 4x = 32, genomes AAFF) between shallot (Allium cepa Aggregatum group) and A. fistulosum were conducted to produce A. cepa - A. fistulosum alien addition lines. When shallot (A. cepa Aggregatum group) was used as a pollinator, the amphidiploids and allotriploids set germinable BC(1) and BC(2) seeds, respectively. The 237 BC(1) plants mainly consisted of 170 allotriploids (2n = 3x = 24, AAF) and 42 hypo-allotriploids possessing 23 chromosomes, i.e., single-alien deletions (2n = 3x-1 = 23, AAF-nF). The single-alien deletions in the BC(1) progeny showed dwarfing characteristics and were discriminated from the allotriploids (2n = 24) and hyper-allotriploids (2n = 25) by means of flow cytometric analysis. The chromosome numbers of 46 BC(2) seedlings varied from 16 to 24. Eight monosomic additions (2n = 2x+1 = 17, AA+nF) and 20 single-alien deletions were found in these BC(2) seedlings. Consequently, six kinds of A. cepa - A. fistulosum alien chromosome additions possessing different chromosome numbers (2n = 17, 18, 20, 21, 22, 23) were recognized in the BC(1) and BC(2) populations. A total of 79 aneuploids, including 62 single-alien deletions, were analyzed by a chromosome 6F-specific isozyme marker (Got-2) in order to recognize its existence in their chromosome complements. This analysis revealed that two out of 62 single-alien deletions did not possess 6F. One (AAF-6F) out of the possible eight single-alien deletions could be identified at first. The present study is a first step toward the development of a useful tool, such as a complete set of eight different single-alien deletions, for the rapid chromosomal assignment of genes and genetic markers in A. fistulosum.     

The use of species-specific DNA markers for assessing alien chromosome transfer in Brassica rapa and Brassica oleracea-monosomic additions of Raphanus sativus

Monosomic addition lines (MALs) are useful materials not only for cytogenetic and molecular genetic studies but also for plant breeding as gene sources. In our previous study, two MALs in the tribe Brassiceae were developed, one being Raphanus sativus lines with alien chromosomes of Brassica rapa (B. rapa-monosomic addition lines; BrMALs) and the second being those with alien chromosomes of Brassica oleracea (B. oleracea-monosomic addition lines; BoMALs). We developed species-specific DNA markers from the genomic sequences of B. rapa and B. oleracea comparing them with those of R. sativus, and identified chromosomes added in BrMALs and BoMALs using these markers. It was revealed that eight types of BrMALs have seven chromosomes of B. rapa and seven types of BoMALs have six chromosomes of B. oleracea. Furthermore, chromosome breakage and homoeologous recombination were suggested to have occurred in some MALs. The developed species-specific DNA markers are considered to be useful for producing MALs and also for assessing chromosome abnormality in MALs.     

Disomic and ditelosomic alien chromosome additions in beet (Beta vulgaris), carrying an extra chromosome of B. procumbens or telosome of B. patellaris.

Alien chromosome transmission through the female germ line as well as meiosis in pollen mother cells were studied in disomic and ditelosomic alien chromosome additions of beet. Beta vulgaris, carrying an extra pair of chromosomes or telosomes of B. procumbens or B. patellaris, respectively. The alien chromosomes carried genes for resistance to the beet cyst nematode, Heterodera schachtii, and screening for this resistance was used to select plants with or without the alien chromosomes. A great variation for alien chromosome transmission was recorded and plants carrying two extra alien chromosomes were recovered in the backcross progenies of the disomic or ditelosomic additions. However, in these progenies the average frequencies of plants without alien chromosomes (86%) did not clearly differ from that in similar progenies of the original monosomic or monotelosomic chromosome additions, indicating that doubling the number of the alien chromosome did not enlarge their transmission to the next generation. The alien chromosomes fully paired at pachytene and desynapsed again before diakinesis, indicating decreased chiasma formation. At second metaphase nearly 60% of the cells had one extra chromosome, and the remaining cells carried two or no extra chromosomes in about equal proportions. The tetrads looked fully normal. The expected relation between the average number of alien chromosomes in the germ cells and in the plants of the progenies did not show up, indicating a strong selection favouring the female gametes without alien chromosomes.     

Diversity of resident plant communities could weaken their allelopathic resistance against alien and native invaders

Biological Invasions - Elton’s classic diversity-invasibility hypothesis posits that diversity of resident communities increases resistance against invaders. We tested whether the...     

Quantifying effects of legal and non-legal designations of alien plant species on their control and profile

Invasive alien species (IAS) pose serious threats to native ecosystems worldwide. In some regions, laws and/or lists related to alien species have been made, but their effects on actual measures against alien species have been little studied. In Japan the IAS act, which came into force in 2005, lists many harmful species under the heading “Designated IAS”. The importation, domestication, sale or release of these species is tightly regulated. In addition, other species are named as alerted alien species (AASs) on the “alien species alert list” to raise public awareness. In this paper we examined the situation in Japan as case study that is exposed to threats from alien species under such laws in recent year to evaluate the effects of that for public interesting. We conducted a survey of the effects of the legal designation and other classification of alien plant species, examining a number of aspects, including research publications, eradications and public awareness. In our analysis, the degree of harmfulness of IASs was considered on the basis of weed risk assessment (WRA). The results show that legal classification of IASs has led to increases in research focused on the designated species, eradication efforts and public awareness. Similar results were also apparent for some AASs, but there was a great deal of variability among the many sub-categories of AASs. This may be partly because AAS sub-categories are based on different premises, and partly because the identification of AASs is not necessarily linked to legal controls that affect the behavior of individuals.     

Frontiers in plant genetics

A report of the American Society for Plant Biologists' meeting 'Plant Genetics 2003: Mechanisms of Genetic Variation', Snowbird, Utah, USA, 22-24 October 2003.     

Frontiers in plant genetics

A report of the American Society for Plant Biologists' meeting 'Plant Genetics 2003: Mechanisms of Genetic Variation', Snowbird, Utah, USA, 22-24 October 2003.     

Gamma irradiation induced deletions in an alien chromosome segment of the wheat 'Indis' and their use in gene mapping.

Deletion mutants were produced in a translocated chromosome segment derived from Thinopyrum distichum (Thunb.) L?ve. Spikes of the translocation line 'Indis' were irradiated with gamma rays at dosages of 15, 20, and 25 Gy. The irradiated spikes were pollinated with 'Inia 66' pollen and the F2 and F3 generations screened for translocation mutants, using the genes for leaf rust resistance and yellow endosperm pigmentation as markers. Finally, endopeptidase polymorphisms were utilized to select mutant translocation homozygotes within each of 29 families. An investigation of polymorphisms at the alpha-Amy-D2 and Wsp-D1 loci of chromosome arm 7DL revealed that 'Indis' did not produce an alpha-AMY-D2 product, but it did produce a novel WSP-D1 protein. The mutants were characterized for their leaf and stem rust resistances and the presence of WSP-D1 and yellow flour pigments. The stem rust resistance gene could not be accurately mapped. The linear order of the remaining loci on 7DL was centromere - leaf rust resistance - Wsp-D1 and yellow pigment. The data obtained suggested that the 'Indis' translocation has homo(eo)logy to the Lr19 translocation and homoeology to 7DL of common wheat.     

Ecological preferences of alien plant species in North-Eastern Germany

The large, comprehensive vegetation database of Mecklenburg-Vorpommern/NE Germany with 51,328 relevés allowed us to study an entire regional flora of 133 non-native plants (NNP, immigration after 1492 AD) with regard to their preferences to all kinds of habitats and along different ecological gradients. For each relevé, we computed average Ellenberg indicator values (EIV) for temperature, light, moisture, reaction, nutrients and salt as well as plant strategy type weights. We partitioned the dataset into relevés with and without occurrences of NNP and compared them with respect to the relative frequencies of EIVs and strategy type weights. We identified deviations from random differences by testing against permuted indicator values. To account for bias in EIV between community types, NNP preferences were differentiated for 34 phytosociological classes. We tested significance of preferences for the group of NNP as a whole, as well as for single NNP species within the entire dataset, as well as differentiated by phytosociological classes and formations. NNP as a group prefer communities with high EIVs for temperature and nutrients and low EIVs for moisture. They avoid communities with low EIV for reaction and high EIV for salt. NNP prefer communities with high proportions of ruderal and low proportion of stress strategists. The differentiation by phytosociological classes reinforces the general trends for temperature, nutrients, moisture, R and S strategy types. Nevertheless, preferences of single species reveal that NNP are not a congruent group but show individualistic ecological preferences.     

Random and fixed effects in plant genetics

Summary A general model for any type of genetic entry is developed which takes into account both the factorial model of gene effects and the ancestral sources, whether inbred lines or outbred varieties, of the genes.Utilizing the model, various genetic designs of fixed entries are explored for the estimation of genetic effects and the testing of genetic hypotheses. These designs consisted of generation means — parents, crosses, various types of backcrosses, and so on — stemming from one or more pairs of parents, and of hybrid combinations from factorial mating designs. Limitations, from the standpoint of genetic effects that can be estimated and genetic hypotheses that can be tested, are developed in considerable detail.When entries from the factorial mating designs are considered to be random, attention is focused on the estimation of genetic variances, rather than effects, and on the concomitant changes in the tests of genetic hypotheses. While there is considerable improvement over fixed entries in the number of types of genetic variances that can be estimated, and of genetic hypotheses that can be tested, they are still very limited in contrast to what would be most desirable.Paper No. 6018 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina. This investigation was supported in part by NIH Research Grant No. GM 11546 from the National Institute of General Medical Sciences.Preliminary: This paper was presented at the 7th International Biometric Conference. Since then it has come to various people's attention and I have been encouraged to give it a wider distribution. Except for editing, the paper is essentially as originally written.     

Cytogenetic identification of Aegilops squarrosa chromosome additions in durum wheat

Summary A set of four normal chromosomes (1D, 2D, 3D, and 6D), and three translocation chromosomes (4DS·5DS, 5DL·7DS, and 7DL·4DL) involving all 14 chromosome arms of the D-genome were obtained as monosomic additions from Aegilops squarrosa (genome D, n=7) in Triticum durum Desf. cv PBW114 (genome AB, n=14). The cyclical translocation occurred during the synthesis of the amphiploid probably as a result of misdivision and reunion of the univalents during meiosis of the F₁ hybrid T. durum x A. Squarrosa. The amphiploid was backcrossed twice with the durum parent to obtain monosomic addition lines. The monosomic addition chromosomes were identified by C-banding and associated phenotypic traits. All monosomic addition lines were fertile. The development of disomic and ditelosomic addition lines is underway, which will be useful for cytogenetic analysis of individual D-genome chromosomes in the background of T. Durum.Contribution No. 90-117-J from the Wheat Genetics Resource Center and Kansas Agricultural Experiment Station, Kansas State University, Manhattan     

Evolutionary genetics of plant adaptation

Plants provide unique opportunities to study the mechanistic basis and evolutionary processes of adaptation to diverse environmental conditions. Complementary laboratory and field experiments are important for testing hypotheses reflecting long-term ecological and evolutionary history. For example, these approaches can infer whether local adaptation results from genetic tradeoffs (antagonistic pleiotropy), where native alleles are best adapted to local conditions, or if local adaptation is caused by conditional neutrality at many loci, where alleles show fitness differences in one environment, but not in a contrasting environment. Ecological genetics in natural populations of perennial or outcrossing plants can also differ substantially from model systems. In this review of the evolutionary genetics of plant adaptation, we emphasize the importance of field studies for understanding the evolutionary dynamics of model and nonmodel systems, highlight a key life history trait (flowering time) and discuss emerging conservation issues.     

Altitudinal distribution of alien plant species in the Swiss Alps

In summer 2003 we recorded the presence and abundance of alien plant species at 232 sites (107 railway stations and 125 road sites) along mountain passes in the Swiss Alps. The altitudinal distribution of species was related to the current abundance of the species in Switzerland and time since introduction. A total of 155 alien taxa were recorded. Numbers of species per site declined exponentially with altitude, and only a few species were found in the alpine zone (>2000 m). In contrast, species richness among comparable native taxa appeared to be nearly independent of altitude over the range investigated. Maximum altitude reached by alien species was related positively to both total area occupied in Switzerland and to time since introduction. A comparison of the results with earlier records suggests that many species, particularly those previously restricted to low or intermediate altitudes, have advanced their altitudinal limits over the past few decades. Various hypotheses are presented to explain the declining abundance of alien species with altitude: low-altitude filter effects, low propagule pressure, and genetic swamping of peripheral populations at higher altitudes. However, at present we do not have sufficient evidence to determine the relative importance of these effects. We conclude that invasion into mountain areas such as the Swiss Alps tends to proceed rather slowly, though the process may be accelerated by climatic warming. For this reason, further research to investigate the processes determining how plants invade mountain areas is urgently needed. And more generally, investigations into the distribution of alien species along strong altitudinal gradients may provide valuable insights into the mechanisms driving the spread of alien organisms.     

植物病原物的群体遗传学

品种单一化、生产密集型和一年多茬的现代农业特点导致病原物呈现出进化速度加快、致病力增强及流行风险增大趋势。深入研究病原物群体遗传学对认识病害的流行、有效选育和使用抗性品种乃至控制病害具有重要意义。文章阐述了植物病原物群体遗传学的研究目标和内容、突变、基因迁移、基因重组、随机遗传漂变和自然选择5大遗传机制在植物病原物进化过程中的作用,以及目前植物病原物群体遗传学研究的现状。