A robust set of black walnut microsatellites for parentage and clonal identification

We describe the development of a robust and powerful suite of 12 microsatellite marker loci for use in genetic investigations of black walnut and related species. These 12 loci were chosen from a set of 17 candidate loci used to genotype 222 trees sampled from a 38-year-old black walnut progeny test. The 222 genotypes represent a sampling from the broad geographic distribution of the species. Analysis of the samples using the 12 loci revealed an average expected heterozygosity of 0.83, a combined probability of identity of 3×10⁻¹⁹, and a combined probability of exclusion for paternity analysis of >0.999. The 222 genotyped trees from the progeny test comprised 39 open-pollinated families, 29 of which (having at least five sampled progeny) were used to estimate the outcrossing rate for the progeny trial. The same 29 families were used to construct a Neighbor-Joining dendrogram based upon allele sharing between individuals. The multilocus estimate of the outcrossing rate was 100% (standard error of zero), higher than the 90% level found in previous studies at the embryo stage, suggesting that both artificial and natural selection against selfs may have occurred over the 38-year lifespan of the progeny trial. In the Neighbor-Joining dendrogram, the majority of the putative siblings grouped together in 21 out of the 29 families, showing that the microsatellites were able to discern most of the family structure in the dataset. Our results indicate that errors were sometimes committed during the establishment of the progeny test. This set of microsatellite loci clearly provides a powerful tool for future applications in black walnut.     

Effects of gibberellin A<Subscript>4/7</Subscript>, 6-benzylaminopurine and chlormequat chloride on the number of male and female strobili and immature cones in Chinese pine (<Emphasis Type="Italic">Pinus tabuliformis</Emphasis>) with foliar sprays

Three kinds of plant growth regulators, gibberellinA 4/7 (GA 4/7 ), 6-benzylaminopurine (BA), and chlormequat chloride (CCC), were evaluated for their ability to promote strobilus and cone production in a Chinese pine (Pinus tabuliformis Carr.) clonal seed orchard. Treatments (0, 250, 500, or 1000 mg L -1 ) were applied during three periods (June- July, July-August and August-September) in 2005. Of the three plant growth regulators, GA 4/7 was the best for promoting flower and cone production. Trees sprayed...     

BKCa-Cav channel complexes mediate rapid and localized Ca2+-activated K+ signaling

Large-conductance calcium- and voltage-activated potassium channels (BKCa) are dually activated by membrane depolarization and elevation of cytosolic calcium ions (Ca2+). Under normal cellular conditions, BKCa channel activation requires Ca2+ concentrations that typically occur in close proximity to Ca2+ sources. We show that BKCa channels affinity-purified from rat brain are assembled into macromolecular complexes with the voltage-gated calcium channels Cav1.2 (L-type), Cav2.1 (P/Q-type), and Cav2.2 (N-type). Heterologously expressed BKCa-Cav complexes reconstitute a functional "Ca2+ nanodomain" where Ca2+ influx through the Cav channel activates BKCa in the physiological voltage range with submillisecond kinetics. Complex formation with distinct Cav channels enables BKCa-mediated membrane hyperpolarization that controls neuronal firing pattern and release of hormones and transmitters in the central nervous system.     

Spatial (Im)mobility and Accessibility in Ireland: Implications for Transport Policy

Recent social research that links people's position in society to their ability to access employment has shown the centrality of spatial mobility in the (re)production of patterns of inequality. This is particularly evident in regions where economic activity is unevenly distributed and concentrated in an urban centre and where daily travel patterns reflect a spatial segregation between places of work and residential areas. This paper presents a spatial analysis of accessibility to employment for Galway City and its environs, a predominantly rural region in the West of Ireland dominated by its urban centre. Travel‐to‐work data from the 2006 Census of Population of Ireland were used to present a comparison of district‐specific accessibility levels across three socio‐economic groups. Network analysis and Geographic Information System visualisation tools are used to map existing socio‐spatial topographies of (in)accessibility. This is done to test two contrasting sets of theoretical proposals in the social science literature regarding the relationship between spatial mobility and social status. Advocates of the first position conceptualise spatial mobility as a form of capital that helps to maintain many existing social hierarchies. This contrasts with the views of those who anticipate the dissolution of established social boundaries (“fluidification”) as a result of increased spatial mobility of people, goods, and ideas. It is argued that these contrasting positions are highly relevant to current transport policy debates, including discussions around the impacts of recession‐related cuts in transport infrastructure investment on patterns of accessibility. In addition, they encourage reflection on the impacts of sustainable transport initiatives on different social groups that are more or less mobility disadvantaged, a fact that has hitherto received little attention in policy research and practice.     

Effectiveness of a detached‐leaf assay as a proxy for stem inoculations in backcrossed chestnut (Castanea) blight resistance breeding populations

A recently developed detached‐leaf blight resistance assay has generated interest because it could reduce the amount of time needed to evaluate backcrossed hybrid trees in the American chestnut blight resistance breeding programme. We evaluated the leaf inoculation technique on a sample of advanced progeny from the Indiana state chapter American Chestnut Foundation breeding programme, along with susceptible American chestnut (Castanea dentata), the recurrent parent, and resistant Chinese chestnut (Castanea mollissima), the donor parent for blight resistance. In experiments over 2 years using two pathogen isolates, we found no biologically meaningful relationship between leaf lesion size and the size (length and width) or severity (1–5 canker severity rating) of stem cankers on 5‐year‐old trees. Chinese chestnuts did develop significantly smaller leaf lesions than American or backcrossed chestnuts. We conclude that while the detached‐leaf assay may have utility in some chestnut breeding applications, it is not a suitable proxy for the established practice of stem inoculations.     

Morphological and molecular methods to identify butternut (Juglans cinerea) and butternut hybrids: relevance to butternut conservation

Butternut (Juglans cinerea L.) is a native, cold-tolerant, hard-mast species formerly valued for its nuts and wood, which is now endangered. The most immediate threat to butternut restoration is the spread of butternut canker disease, caused by the exotic fungus Sirococcus clavigignenti-juglandacearum Nair, Kostichka & Kuntz. Other threats include the hybridization of butternut with the exotic Japanese walnut (Juglans ailantifolia Carr.) and poor regeneration. The hybrids, known as buartnuts, are vegetatively vigorous, highly fecund, more resistant than butternut to butternut canker disease and difficult to identify. We review the vegetative and reproductive morphological traits that distinguish butternut from hybrids and identify those that can be used by field biologists to separate the taxa. No single trait was sufficient to separate butternut from hybrids, but pith color, lenticel size, shape and abundance, and the presence or absence of a notch in the upper margin of leaf scars, can be used in combination with other traits to identify butternuts and exclude most hybrids. In at least one butternut population, reduced symptoms of butternut canker disease were significantly associated with a dark barked phenotype. We also describe two randomly amplified polymorphic DNA (RAPD) markers that differentiate butternuts from hybrids based on DNA polymorphism. Together, these results should assist in the identification and testing of non-hybrid butternut for breeding and reintroduction of the species to its former habitats.     

Genotypic data changes family rank for growth and quality traits in a black walnut (Juglans nigra L.) progeny test

We evaluated eight-year-old seedlings in a black walnut (Juglans nigra L.) progeny test for two quantitative and two qualitative traits. We also used 12 microsatellite markers to genotype the 328 progeny and their maternal parents. Seedling family growth and quality was evaluated based on the progeny test map. These values were compared to family growth and quality after seedlings were genotyped and reassigned to families by parentage assignment software. After genotyping and parentage analysis, about 80 % of the offspring were assigned to the same half-sib family indicated on the planting map. Considerable differences were observed between the ranks of half-sib families based on the planting-map versus the ranks of the families based on the exclusion/assignment of progeny to their family based on genotypes. Analysis of the data without genotypic assignment of progeny to their correct family revealed that the family effect for height was significant, as was family effect for diameter. After seedlings were reassigned to half-sib families based on genotypic information, neither the family effect for height nor the family effect for diameter was significant. The efficiency of the mixed model ANOVA, as measured by Akaike Information Criterion improved by about 30 % after genotyping and exclusion/reassignment of progeny. These results show that genotyping progeny can have a significant effect on the rank of families and potential selection of individuals from a progeny trial, the quality of data analysis, and the efficiency and efficacy of breeding operations.     

Herd specific risk factors for Mycoplasma hyopneumoniae infections in suckling pigs at the age of weaning

Background

Mycoplasma hyopneumoniae is the etiologic agent of enzootic pneumonia mainly occurring in fattening pigs. It is assumed that horizontal transmission of the pathogen during nursery and growing phase starts with few suckling pigs vertically infected by the sow. The aim of the present study was the exploration of the herd prevalence of M. hyopneumoniae infections in suckling pigs followed by an investigation of various herd specific factors for their potential of influencing the occurrence of this pathogen at the age of weaning.

Results

In this cross-sectional study, 125 breeding herds were examined by taking nasal swabs from 20 suckling pigs in each herd. In total, 3.9% (98/2500) of all nasal swabs were tested positive for M. hyopneumoniae by real-time PCR. Piglets tested positive originated from 46 different herds resulting in an overall herd prevalence of 36.8% (46/125) for M. hyopneumoniae infection in pigs at the age of weaning. While the herds were epidemiologically characterized, the risk for demonstration of M. hyopneumoniae was significantly increased, when the number of purchased gilts per year was more than 120 (OR: 5.8), and when the number of farrowing pens per compartment was higher than 16 (OR: 3.3). In herds with a planned and segregated production, where groups of sows entered previously emptied farrowing units, the risk for demonstration of M. hyopneumoniae in piglets was higher in herds with two or four weeks between batches than in herds with one or three weeks between batches (OR: 2.7).

Conclusions

In this cross-sectional study, several risk factors could be identified enhancing the probability of breeding herds to raise suckling pigs already infected with M. hyopneumoniae at the time of weaning. Interestingly, some factors (farrowing rhythm, gilt acclimatisation issues) were overlapping with those also influencing the seroprevalences among sows or the transmission of the pathogen between older age groups. Taking the multifactorial character of enzootic pneumonia into account, the results of this study substantiate that a comprehensive herd specific prevention programme is a prerequisite to reduce transmission of and disease caused by M. hyopneumoniae.     

Genetic diversity and differentiation of yellowwood [<Emphasis Type="Italic">Cladrastis kentukea</Emphasis> (Dum.Cours.) Rudd] growing in the wild and in planted populations outside the natural range

Yellowwood (Cladrastis kentukea) grows in small, widely scattered populations in the wild, but is also a popular ornamental tree that thrives when planted in urban areas outside its natural range. Since the small native populations of yellowwood in several states are considered at risk of extirpation, the cultivated population could serve as an ex situ repository of yellowwood genetic diversity that could be used to restore lost local populations of the species. The potential value of cultivated yellowwood for conservation depends on the genetic diversity among cultivated trees compared to natural populations. Using nuclear microsatellite markers, we genotyped 180 yellowwoods from natural populations in Indiana, Missouri, Arkansas, and Kentucky, along with 61 trees from urban parks and landscapes in Indiana, Ohio, and Missouri. We found that, even when statistics were adjusted based on population size, the urban “population” had higher genetic diversity than any of the wild populations sampled, indicating that commercially-grown yellowwood is most likely a mixture of genotypes from isolated wild populations. We observed strong genetic differentiation among wild populations, and evidence for inbreeding in at least one of the wild populations.