Genetic variation in partial resistance to leaf rust in winter wheat: disease progress,foliage senescence and yield reduction

Relations between leaf rust progress, foliage senescence and yield reduction were studied for seven winter wheat genotypes, differing in their partial resistance to leaf rust. Leaf rust accelerated leaf and ear senescence. Photosynthesis measurements showed, however, that the photosynthetic capacity of the remaining green surface was not affected. Differences between genotypes in yield reduction were largely explained by differences in leaf senescence and, therefore, in cumulative light interception (r=0.83) and crop photosynthesis. Reduction in cumulative light interception was closely related to the area under the disease-progress-curve (r=0.85), which was also closely associated with yield reduction (r=0.88). However, the time taken to reach a 50% reduction of green leaf area and the pustule density on 1 July (i.e. halfway through the epidemic) were just as good predictors of yield reduction as cumulative light interception and area under disease-progress-curve, suggesting that the former are useful criteria in the selection for partial resistance to leaf rust.Samenvatting De relatie stussen de epidemiologie van bruine roest, bladveroudering en oprengstderving werden bestudeerd bij zeven wintertarwegenotypen die verschilden in partiële resistentie tegen bruine roest. Bruine roest versnelde de veroudering van blad en aar. Fotosynthesemetingen wezen echter uit dat de fotosynthesecapaciteit van het resterende groene oppervlak niet werd beïnvloed. Verschillen tussen de genotypen in opbrengstderving werden voornamelijk veroorzaakt door verschillen in bladveroudering en daarmee in cumulatieve lichtinterceptie (r=0.83) en gewasfotosynthese. De reductie in cumulatieve lichtinterceptie was nauw gerelateerd aan de cumulatieve ziektedruk (in puistdagen) (r=0.85), welke ook nauw was geassocieerd met de opbrengstderving (r=0.88). De opbrengstreductie werd echter even goed voorspeld door de tijdsduur tot 50% reductie van het groene bladoppervlak en de puistdichtheid halverwege de epidemie als door cumulatieve lichtinterceptie en cumulatieve ziektedruk, waardoor beide eerste criteria gebruikt kunnen worden in de selectie voor partiële resistentie tegen bruine roest.     

Spreading of spray mixtures on leaf surfaces: II. cohesive interaction parameters as predictors of spreading and the effect of molar volume and roughness on spreading

Partial cohesive interaction parameters as predictors of the spreading of spray mixtures were investigated. Multiple linear regression of the inverse of the area of spread, 1/A, for leaf surfaces on the partial cohesive interaction parameters of pure liquids gave a good fit (r² > 0–90) on virtually all tested surfaces. The coefficients obtained from the regression analysis could be used to describe the spreading properties of each surface uniquely. Regression of 1/Afor an unknown liquid on the coefficients of known surfaces could, conversely, be used to obtain the cohesive interaction parameters of the unknown liquid. A linear relationship was observed between the calculated energy of adsorption and the inverse of the area of spread. An increase in molar volume caused a decrease in the slope of the regression line and an increase in roughness caused a similar, but more pronounced, decrease.     

A structure model and growth mechanism for multishell carbon nanotubes

A model that postulates a mixture of scroll-shaped and concentric, cylindrical graphene sheets is proposed to explain the microstructure of graphite multishell nanotubes grown by arc discharge. The model is consistent with the observed occurrence of a relatively small number of different chiral angles within the same tubule. The model explains clustering in a natural way and is consistent with the observation of asymmetric (0002) lattice fringe patterns and with the occurrence of singular fringe spacings larger than c/2 (c is the c parameter of graphite) in such patterns. Anisotropic thermal contraction accounts for the 2 to 3 percent increase in the c parameter of nanotubes, compared with bulk graphite, but is too small to explain the singular fringe spacings. The model also explains the formation of multishell closure domes. Nucleation is attributed to the initial formation of a fullerene "dome."     

Congenital bilateral aplasia of the metacarpophalangeal joints in a foal

A 2‐day‐old Warmblood filly was presented for examination of an angular limb deformity of the left front limb and an upright conformation of both metacarpophalangeal joints. Radiological examination revealed bilateral absence of the metacarpophalangeal joint space with fusion of the third metacarpal bone and first phalanx (synostosis). No treatment was undertaken. The filly was readmitted to the clinic 10 weeks later for bilateral front limb lameness. On radiological examination, the synostosis of the front metacarpophalangeal joints was still present. Physitis of the distal growth plate of the right third metacarpal bone and proximal growth plate of the right proximal phalanx, and an avulsion fracture of the palmaromedial and proximal aspect of the left middle phalanx, with a cystic like lesion on the medial aspect of distal first phalanx and proximal middle phalanx were diagnosed. Given the poor prognosis, the foal was subjected to euthanasia. Post mortem examination confirmed the absence of the metacarpophalangeal joint space with a trabecular bony union between the third metacarpal bone and the first phalanx. A rudimentary joint capsule was present at the level of the absent joints as well as a small zone of articular cartilage, which invaginated over a short distance into the dorsal trabecular bone on the right front limb. On the medial aspect of the left proximal interphalangeal joint, a focal defect of articular cartilage with exposure of subchondral bone was observed. This is the first case report of a foal born with congenital aplasia of both metacarpophalangeal joints. Congenital malformations should be considered as differential diagnosis in lame foals or foals born with angular or flexural limb deformities.     

Quantifying spatiotemporal drivers of environmental heterogeneity in Kruger National Park,South Africa

Context

Environmental heterogeneity is considered an important mechanism of biodiversity. How environmental heterogeneity is characterised by the compositional, structural and functional variation of biotic and abiotic components is a central research theme in conservation.

Objectives

We explore how environmental heterogeneity relates to the underlying physical landscape template and how that relationship changes over space and time. We examine how, in some areas, environmental heterogeneity may also be driven by dynamic ecological processes, and how this relates to patterns of plant species richness.

Method

We use local geographically weighted regression to spatially partition environmental heterogeneity, measured as Landsat spectral variance, into the portion explained by stable physical landscape properties (R²) and the portion unexplained (1?R²) which we term landscape complexity. We explore how this relationship varies spatially and temporally as a function of dynamic ecological processes such as rainfall and season in Kruger National Park, as well as plant species richness at landscape scales.

Results

The significance and direction of relationships varied over space and time and as a function of rainfall and season. R² values generally decreased in higher rainfall summer months and revealed patterns describing the importance of known stable factors relative to unknown dynamic factors. Landscape complexity (1?R²) explained over 70 % of variation in species richness.

Conclusions

Rainfall and seasonality are important drivers of environmental heterogeneity. The spatial arrangement and magnitude of model agreement helped disentangle the relative influence of the physical landscape template on environmental heterogeneity. Given the high correlation with species richness, landscape complexity provides complementary guidance to biodiversity research and monitoring prioritization.

     

Network analysis of wildlife translocations in New Zealand

AIMS: To identify network measures with relevance to disease spread in a network of movements derived from the Department of Conservation (DOC) translocation records from 1970 to mid-2014, and to identify conservation sites that should be prioritised for surveillance activities and improvements to data collection to make the best use of network analysis techniques in the future.

METHODS: Data included the source and destination of translocated specimens, the species and the dates the translocations were expected to occur. The data were used to construct a directed, non-weighted network in which a translocation event represented a tie in the network. Network density, in-degree (movements entering a node of interest) and out-degree (movements leaving a node of interest) and reciprocity were calculated.

RESULTS: The data analysed consisted of 692 unique translocations between 307 sites, with the majority (518; 73%) being for birds. The constructed network for bird, reptile and frog translocations comprised 260 nodes, with 34/260 (13%) having two-way movements and 47/260 (18%) non-reciprocal movements. The median degree score (sum of in- and out-degree) was two (min 0, max 36) with a mean of 3.5 in a right skewed distribution. Most sites acted as receivers or senders of consignments with only a few having both high in- and high out-degree, and thus had characteristics that made them sites of interest for surveillance activities. These included the National Wildlife Centre at Mount Bruce, Tiritiri Matangi Island and Te Kakahu (Chalky Island).

CONCLUSIONS: The presence of linking sites that join larger clusters within the network creates the potential for rapid disease spread if a pathogen were to be introduced. The important sites that supply or receive specimens for translocations are already well recognised by those performing translocations in New Zealand, and this paper provides further information by quantifying their role within the network.