Screening techniques and sources of resistance to root diseases in cool season food legumes

Summary Soil-borne fungal diseases are among the most important factors, limiting the yield of grain legumes in many countries worldwide. Root rot, caused by Aphanomyces euteiches, Rhizoctonia solani, Fusarium solani and wilt, caused by several formae speciales of Fusarium oxysporum are the most destructive soil-borne diseases of pea, chickpea, lentil, fababean and lupin. The most effective control of these diseases is achieved through the use of resistant varieties. In this paper, recent advances in conventional and innovative screening methods for disease resistance are presented. Many grain legume accessions, which are maintained in national and international germplasm collections, have been evaluated for disease resistance and numerous resistant varieties have been released following incorporation of identified resistance genes from these sources. Recent identification of molecular markers tightly linked to resistance genes has greatly enhanced breeding programs by making marker assisted selection (MAS) possible and allowing the development of varieties with multiple disease resistance. Progress in the understanding of the biology of soil-borne fungal pathogens of grain legumes is also reviewed with particular reference to the genetic structure of their populations, diagnosis and host–pathogen interaction.     

A new yam bean (Pachyrhizus spp.) interspecific hybrid

The yam bean (Pachyrhizus spp.) is a legume tuber / root crop locally grown in Central America, South America and Asia. The tuber is usually consumed raw for its refreshing taste and high moisture content. A recently found P. tuberosus type from a small ecogeographic region in the tropical lowlands of Peru has a high tuber dry matter content and this so-called Chuin-Type is consumed like manioc. This study was conducted to determine the possibility to use the Chuin-Type as a source to incorporate high dry matter into the remaining yam bean gene pool. Three P. tuberosus (Chuin) accessions were crossed with 15 P. ahipa accessions from the Andean highlands resulting in six successful interspecific hybridisations. Successful crosses were confirmed by morphological and agronomical traits as well as multivariate statistics. All hybrid plants were fertile and vigorous. Owing to the fertility and vigour of interspecific hybrids it is assumed that a hybrid between P. tuberosus and P. ahipa might already evolved in the area of origin and that interspecific hybridisation is appropriate to improve the tuber dry matter content in the yam bean which might give the crop new forms of food and processing use.     

Zytologische und embryologische Untersuchungen am Nucellus apomiktischer Sippen der Wiesenrispe (Poa pratensis L.)

Zusammenfassung Bei apomiktischen Sippen vonPoa pratensis wurden 165 Samenanlagen auf die Anzahl der in ihren Nucelli ausgebildeten Embryosäcke untersucht. Dabei wurden in 87 Nucelli ein, in 60 zwei und in 18 drei Embryosäcke gefunden. Im Einzelfall sind in diesem Stadium apomiktische von sexuellen Embryosäcken nicht zu unterscheiden; es kann aber aus der bekannten hohen Apomixierate bei Zuchtmaterial geschlossen werden, daß es sich dabei fast ausnahmslos um solche aposporen Ursprungs handelt.Die zahlenmäßige Erfassung keimfähiger mono-, bi- und polyembryonaler Karyopsen erfolgt im Keimapparat auf Filterpapier. Die auf diese Weise ermittelte Differenz zu den mittels embryologischer Methoden erfaßten Embryosäcken ist beträchtlich. Von der Anzahl aposporer Initialen je Nucellus über die Anzahl entwickelter Embryosäcke je Nucellus bis zur Ausbildung keimfähiger Embryonen je Karyopse, ist zahlenmäßig eine starke Verminderung festzustellen.In dem befruchtungsfähigen Embryosack bilden, wie zu erwarten, drei Kerne den Eiapparat, zwei die Polkerne und drei die Antipoden. Durch somatische Polyploidisierung erfahren die Antipoden stets eine auffällige Volumenzunahme, und es kann sich durch zusätzliche Teilungen auch ihre Anzahl erhöhen.

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Cytological and embryological studies in nucelli of apomictic specimens ofPoa pratensis L.

Summary In a total of 165 analysed nucelli of apomictic specimens ofPoa pratensis 87 contain only one embryo-sac, 60 two embryo-sacs and 18 three ones. In no case aposporous embryo-sacs could be distinguished from meiotic ones. However, from the high apomeiotic rate in breeding material the conclusion can be drawn that the majority of them are of aposporous origin.The numerical evaluation of the germinating capacity of mono-, bi- and polyembryonic caryopses was performed in a germinating apparatus. There are considerable differences between the values determined in this way and those ascertained by embryological methods. It was found that during the developmental pathway from the aposporous initial to the mature, full-grown embryo sequentially the number of embryo-sacs per nucellus and the number of embryos capable to germinate per caryopsis are diminished.As expected, in the mature, fertile embryo-sac three nuclei form the egg-apparatus, two ones the pole nuclei and three ones the antipodals. By somatic polyploidization the antipodals always undergo a considerable increase in volume, and in few cases by additional divisions the number of antipodals may be increased also.

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(Poa pratensis L.)

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Paleo-Eskimo mtDNA genome reveals matrilineal discontinuity in Greenland

The Paleo-Eskimo Saqqaq and Independence I cultures, documented from archaeological remains in Northern Canada and Greenland, represent the earliest human expansion into the New World's northern extremes. However, their origin and genetic relationship to later cultures are unknown. We sequenced a mitochondrial genome from a Paleo-Eskimo human by using 3400-to 4500-year-old frozen hair excavated from an early Greenlandic Saqqaq settlement. The sample is distinct from modern Native Americans and Neo-Eskimos, falling within haplogroup D2a1, a group previously observed among modern Aleuts and Siberian Sireniki Yuit. This result suggests that the earliest migrants into the New World's northern extremes derived from populations in the Bering Sea area and were not directly related to Native Americans or the later Neo-Eskimos that replaced them.     

Consequences of adult and juvenile movement for marine protected areas

Adult and juvenile mobility has a considerable influence on the functioning of marine protected areas. It is recognized that adult and juvenile movement reduces the core benefits of protected areas, namely protecting the full age–structure of marine populations, while at the same time perhaps improving fisheries yield over the no-reserve situation through export of individuals from protected areas. Nevertheless, the study of the consequences of movement on protected area functioning is unbalanced. Significant attention has been paid to the influence of certain movement patterns, such as diffusive movement and home ranges, while the impacts of others, such as density-dependent movements and ontogenetic migrations, have been relatively ignored. Here we review the diversity of density-independent and density-dependent movement patterns, as well as what is currently known about their consequences for the conservation and fisheries effects of marine protected areas. We highlight a number of ‘partially addressed’ issues in marine protected area research, such as the effects of reserves targeting specific life phases, and a number of essentially unstudied issues, such as density-dependent movements, nomadism, ontogenetic migrations, behavioral polymorphism and ‘dynamic’ reserves that adjust location as a realtime response to habitat changes. Assessing these issues will be essential to creating effective marine protected area networks for mobile species and accurately assessing reserve impacts on these species.     

Larval performances and life cycle completion of the Siberian moth, <Emphasis Type="Italic">Dendrolimus sibiricus</Emphasis> (Lepidoptera: Lasiocampidae), on potential host plants in Europe: a laboratory study on potted trees

The Siberian moth, Dendrolimus sibiricus, Tschtv. is the most harmful defoliator of coniferous forests in North Asia. The pest has already spread over the Urals and continues moving westwards. Recently, it has been recommended for quarantine in member countries by European and Mediterranean Plant Protection Organization (EPPO). The performances of the pest on coniferous species planted in Europe were assessed on a range of potted trees corresponding to the spectrum of economically important conifers in the EU: European larch Larix decidua, Norway spruce Picea abies, Scots pine Pinus sylvestris, European black pine Pinus nigra, and the North American species: Douglas fir Pseudotsuga menziesii and grand fir Abies grandis. Larvae showed a potential to survive and complete the development on all these host tree species. Favorable hosts were grand fir, European larch, and Douglas fir that allowed higher survival, better larval development, and as a result, yielded heavier pupae and adult moths with higher longevity. Black pine was a poor host but, however, could still support larval and pupal development. Norway spruce and Scots pine had an intermediate behavior. If accidentally introduced to Europe, the Siberian moth may become especially damaging in forest stands predominated by European larch and by the North American firs. Norway spruce and especially the two-needle pines will be less prone to intensive defoliation by this species. The fact that the pest may damage the range of economically important coniferous species should be taken into account in the pest risk assessment for Europe and also for North America where the Siberian moth occurrence is considered likely.     

Cryptic speciation in Hymenoscyphus albidus

Ash dieback caused by the mitosporic ascomycete Chalara fraxinea is a novel disease of major concern affecting Fraxinus excelsior and Fraxinus angustifolia in large parts of Europe. Recently, its teleomorph was detected and assigned to Hymenoscyphus albidus, which has been known from Europe since 1851. In this study, we present molecular evidence for the existence of two morphologically very similar taxa, H. albidus, which is lectotypified and Hymenoscyphus pseudoalbidus sp. nov. Differences were found between the species in the loci calmodulin, translation elongation factor 1‐α and the internal transcribed spacers of the rDNA genes, and strong differentiation was obtained with ISSR markers. It is likely that H. albidus is a non‐pathogenic species, whereas H. pseudoalbidus is a virulent species causing ash dieback. Genotyping herbarium specimens showed that H. pseudoalbidus has been present in Switzerland for at least 30 years prior to the outbreak of the epidemic.     

Genetic diversity, inbreeding and breeding practices in dogs: results from pedigree analyses

Pedigree analysis constitutes a classical approach for the study of the evolution of genetic diversity, genetic structure, history and breeding practices within a given breed. As a consequence of selection pressure, management in closed populations and historical bottlenecks, many dog breeds have experienced considerable inbreeding and show (on the basis of a pedigree approach) comparable diversity loss compared to other domestic species. This evolution is linked to breeding practices such as the overuse of popular sires or mating between related animals. The popular sire phenomenon is the most problematic breeding practice, since it has also led to the dissemination of a large number of inherited defects. The practice should be limited by taking measures such as restricting the number of litters (or offspring) per breeding animal.