Modified full-sib selection and best linear unbiased prediction of progeny performance in a European F2 maize population

Four cycles of modified recurrent full‐sib (FS) selection were conducted in an intermated F₂ population of European flint maize. The objectives of our study were to monitor trends across selection cycles in the estimates of population mean, inbreeding coefficients and variance components, and to investigate the usefulness of best linear unbiased prediction (BLUP) of progeny performance under the recurrent FS selection scheme applied. We used a selection rate of 25% for a selection index, based on grain yield and dry matter content. A pseudo‐factorial mating scheme was used for recombination. In this scheme, the selected FS families were divided into an upper‐ranking group of parents mated to the lower‐ranking group. Variance components were estimated with restricted maximum likelihood (REML). Average grain yield increased 1.2 t/ha per cycle, average grain moisture decreased 20.1 g/kg per cycle, and the selection index relative to the F₂ check entries decreased 0.3% per cycle. For a more precise calculation of selection response, the four cycles should be tested together in multi‐environmental trials. We observed a significant decrease in additive variance in the selection index, suggesting smaller future selection response. Predictions of FS family performance in Cn + 1 based on mean performance of parental FS families in Cn were of equal precision as those based on the mean additive genetic BLUP of their parents, and corresponding correlations were of moderate size for grain moisture and selection index.     

Seal lungs collapse during free diving: evidence from arterial nitrogen tensions

Arterial blood nitrogen tensions of free-diving Weddell seals (Leptonychotes weddelli) were measured by attaching a microprocessor-controlled blood pump and drawing samples at depth to determine how these marine mammals dive to great depths and ascend rapidly without developing decompression sickness. Forty-seven samples of arterial blood were obtained from four Weddell seals during free dives lasting up to 23 minutes to depths of 230 meters beneath the sea ice of McMurdo Sound, Antarctica. Peak arterial blood nitrogen tensions of between 2000 and 2500 millimeters of mercury were recorded at depths of 40 to 80 meters during descent, indicating that the seal's lung collapses by 25 to 50 meters. Then arterial blood nitrogen tensions slowly decreased to about 1500 millimeters of mercury at the surface. In a single dive, alveolar collapse and redistribution of blood nitrogen allow the seal to avoid nitrogen narcosis and decompression sickness.     

Rye introgression lines as source of alleles for pollen-fertility restoration in Pampa CMS

Restoration of pollen-fertility is required to guarantee successful seed production of hybrid varieties based on cytoplasmatic male-sterility (CMS) induced by Pampa cytoplasm. As most European restorer lines have still numerous disadvantages, using genetic resources via introgression libraries might be promising to identify and localize new and more effective restorer genes. The objectives of this study were to (1) evaluate in field trials the performance of 39 candidate introgression lines (pre-ILs) for pollen-fertility restoration and (2) to identify donor chromosome segments (DCS) underlying pollen-fertility restoration. Exotic alleles from the Iranian primitive rye accession Altevogt 14160 were introduced into the elite non-restorer inbred line L2053-N by marker-assisted backcrossing. BC₂S₃ pre-ILs were genotyped using amplified fragment length polymorphisms and simple sequence repeats. Pollen-fertility restoration was evaluated in replicated field trials across two testers at two locations in 2006 for analysing the phenotypic effects of the exotic DCS. Out of 39 pre-ILs, we determined three showing full pollen-fertility across both testers and locations carrying a DCS on chromosome 4R. Moreover, one pre-IL with partial pollen-fertility was detected showing a DCS on chromosome 1R. We conclude that our introgression library can serve as a valuable resource for mining favourable genes from exotic primitive rye, which can greatly promote hybrid rye breeding.     

SIMBLIGHT1 – a new model to predict first occurrence of potato late blight*

Prediction of the first occurrence of potato late blight (Phytophthora infestans) given by the SIMPHYT1 model, which has been used for about 20 years, has not been found satisfactory in years with high soil moisture. Consequently, a new model, SIMBLIGHT1, has been developed. As input parameters SIMBLIGHT1 requires temperature, relative humidity and information on soil moisture, crop prevalence and cultivar susceptibility. SIMBLIGHT1 calculates a cumulative risk index for several groups of emergence dates and signals the start of the epidemic once a given threshold is overridden. Model validation and comparison of SIMBLIGHT1 with SIMPHYT1 were performed with field data from 11 years. Results were promising and SIMBLIGHT1 gave better results than SIMPHYT1 when soils of potato fields were waterlogged. Efforts are currently being made to improve SIMBLIGHT1 and in the long term this model will replace SIMPHYT1.     

Modelling of stream fishes in the Great Plains, USA

Abstract –  Predicting species distributions has important implications for the conservation and management of freshwater fishes, particularly in areas such as the Great Plains, USA where human impacts have resulted in extirpations and declines for numerous native species. There are a number of statistical approaches for constructing distributional models; the accuracy of each is likely dependent on the nature of the environmental gradients, species responses to those gradients and the spatial extent of the modelling. Thus, it is important to compare multiple approaches across species and habitats to identify the most effective modelling approach. Using geographical information system (GIS) derived characteristics of stream segments as predictors, we tested the model performance of three methodologies – linear discriminant function analysis, classification trees and artificial neural networks (ANN) – for predicting the occurrence of 38 fish species in a Great Plains river basin. Results showed that all approaches predicted species occurrences with relatively high success. ANN generally were the best models, in that they generated the most significant models (35 of 38 species) and most accurately predicted species presence for the greatest number of species (average correct classification = 81.1%). The importance of GIS variables for predicting stream fish occurrences varied among species and modelling techniques, but were generally strong predictors of species distributions, including the federally endangered Topeka shiner Notropis topeka . In summary, predictive models should be viewed as both competitive and complementary methodologies for establishing quantitative linkages between fish species and their environment. Our study demonstrates the potential utility of such an approach for guiding conservation efforts for stream fishes of the Great Plains, USA.     

Global flexibility in a sensory receptor: a site-directed cross-linking approach

The aspartate receptor of Escherichia coli and Salmonella typhimurium is a cell surface sensory transducer that binds extracellular aspartate and sends a transmembrane signal to the inside of the bacterium. The flexibility and allostery of this receptor was examined by placing sulfhydryl groups as potential cross-linking sites at targeted locations in the protein. Seven different mutant receptors were constructed, each containing a single cysteine residue at a different position in the primary structure. Intramolecular disulfide bond formation within oligomers of these mutant receptors is shown to trap structural fluctuations and to detect ligand-induced changes in structure. The results indicate that the receptor oligomer has a flexible, dynamic structure which undergoes a global change upon aspartate binding.     

Identification of genomic regions carrying QTL for agronomic and quality traits in rye (Secale cereale) introgression libraries

Introgression libraries can be used to localize genomic regions carrying quantitative trait loci (QTL). We used this approach to detect QTL regions affecting the per se performance of agronomic and quality traits with two rye (Secale cereale L.) introgression libraries. Our objectives were to detect candidate introgression lines (pre‐ILs) that have a different per se performance than the recurrent parent and to identify the underlying QTL regions. The introgression libraries containing 40 BC₂S₃ lines each were established with marker‐assisted backcrossing from crosses of the heterozygous Iranian primitive rye accession Altevogt 14160 and the elite inbred line L2053‐N. To assess the phenotypic effect of the donor chromosome segments (DCS) the pre‐ILs were evaluated for grain yield, plant height, thousand‐kernel weight, test weight, falling number and protein content in replicated field trials at five locations in Germany over 2 years. In total, 58 significant (P < 0.05) differences between pre‐ILs and L2053‐N were observed in each introgression library. The DCS in pre‐ILs differing from the recurrent parent possess most likely the responsible QTL. Genomic regions carrying favourable QTL alleles were detected for test weight, thousand‐kernel weight and protein content. We conclude that Altevogt 14160 can not only be used to enrich the genetic variation of the restricted hybrid rye gene pools but will also allow the breeder to efficiently detect favourable QTL for marker‐assisted selection.