Evaluation of three tractor-guidance methods for parallel swathing at two field speeds

This study compared the accuracy (mean error and rms error) and precision (standard deviation of error) of three tractor-guidance methods (foam-marker, light-bar, and assisted-steering systems) at two field speeds (5.6 – and 11.5 km/h) for parallel swathing operations. Eighty-four replications of each combination of guidance method and field speed were conducted between 15 October and 22 December 2006 (504 total field passes). The foam-marker system was found to be significantly less accurate [larger mean error (p \u3c .0001) and had a larger rms error (p \u3c .0001)] than either the light-bar or the assisted-steering system. There was no significant difference in mean error (p = .6718) or rms error (p = .8841) by field speed. There was a significant interaction between guidance method and field speed for both mean error (p = .0009) and rms error (p = .003). Mean and rms errors for the foam-marker and the assisted-steering systems increased at higher field speed, while the mean and rms errors for the light-bar system decreased at higher speed. The assisted-steering system had a significantly lower (p = .0164) standard deviation of error (higher precision) than the foam-marker or the light-bar systems. There was no significant difference in the standard deviation of error by field speed (p = .6258) or by the interaction of guidance method and field speed (p = .2748)

Two Evolutionary Histories in the Genome of Rice: the Roles of Domestication Genes

Genealogical patterns in different genomic regions may be different due to the joint influence of gene flow and selection. The existence of two subspecies of cultivated rice provides a unique opportunity for analyzing these effects during domestication. We chose 66 accessions from the three rice taxa (about 22 each from Oryza sativa indica, O. sativa japonica, and O. rufipogon) for whole-genome sequencing. In the search for the signature of selection, we focus on low diversity regions (LDRs) shared by both cultivars. We found that the genealogical histories of these overlapping LDRs are distinct from the genomic background. While indica and japonica genomes generally appear to be of independent origin, many overlapping LDRs may have originated only once, as a result of selection and subsequent introgression. Interestingly, many such LDRs contain only one candidate gene of rice domestication, and several known domestication genes have indeed been “rediscovered” by this approach. In summary, we identified 13 additional candidate genes of domestication

The population genomics of begomoviruses: global scale population structure and gene flow

<p>Abstract</p> <p>Background</p> <p>The rapidly growing availability of diverse full genome sequences from across the world is increasing the feasibility of studying the large-scale population processes that underly observable pattern of virus diversity. In particular, characterizing the genetic structure of virus populations could potentially reveal much about how factors such as geographical distributions, host ranges and gene flow between populations combine to produce the discontinuous patterns of genetic diversity that we perceive as distinct virus species. Among the richest and most diverse full genome datasets that are available is that for the dicotyledonous plant infecting genus, <it>Begomovirus</it>, in the Family Geminiviridae. The begomoviruses all share the same whitefly vector, are highly recombinogenic and are distributed throughout tropical and subtropical regions where they seriously threaten the food security of the world's poorest people.</p> <p>Results</p> <p>We focus here on using a model-based population genetic approach to identify the genetically distinct sub-populations within the global begomovirus meta-population. We demonstrate the existence of at least seven major sub-populations that can further be sub-divided into as many as thirty four significantly differentiated and genetically cohesive minor sub-populations. Using the population structure framework revealed in the present study, we further explored the extent of gene flow and recombination between genetic populations.</p> <p>Conclusions</p> <p>Although geographical barriers are apparently the most significant underlying cause of the seven major population sub-divisions, within the framework of these sub-divisions, we explore patterns of gene flow to reveal that both host range differences and genetic barriers to recombination have probably been major contributors to the minor population sub-divisions that we have identified. We believe that the global <it>Begomovirus </it>population structure revealed here could facilitate population genetics studies into how central parameters of population genetics namely selection, recombination, mutation, gene flow, and genetic drift shape the global begomovirus diversity.</p

Mental and Physical Health Predictors After Romantic Betrayal

Participants were 123 victims of romantic betrayal (55 males/68 females, mean age = 34.8 years) who volunteered to be in the study in exchange for monetary compenation. Each completed a questionnaire that asked participants to describe their worst experience as a victim of romantic betrayal, and to complete a widely used measure of adult attachment (Hazan & Shaver, 1987) and a checklist of mental/physical health symptoms experienced within the first month after betrayal. Participants were divided into three groups based on the attachment measure, yielding groups of avoidantly attached (those who feel very uncomfortable with intimacy and lack basic trust in others), anxious-ambivalently attached (those who are nervous about intimacy but seek it anyway to quell their doubts), and securely attached individuals (those who are comfortable with intimacy and trusting of their partners). Using a multivariate analysis of variance (MANOVA) technique, the three groups were compared to determine if attachment style was related to the number of mental and physical health symptoms reported by victims. Results indicated that securely attached individuals reported significantly fewer symptoms of major depression and serious anxiety reactions after betrayal, as well as fewer physical health symptoms, than those who were avoidantly attached. Implications for identification and treatment of individuals who are at risk for mental and physical health problems after betrayal will be discussed