A Genetic Linkage Map of Brassica rapa Based on AFLP Markers

A F2 mapping population was developed by crossing a Chinese cabbage-pe-tsai variety CC156 and an oil type Rapid cycling RC144 which were different from each other in morphology, maturity, self-compatibility, plant height, etc. Using 244 AFLP markers a map was constructed containing 10 main linkage groups covering a total distance of 857 cM,corresponding to 3.5 cM per marker. Length of linkage groups varied from 43 to 125 cM and the number of AFLP markers linkage to each group ranged from 7 to 41.     

Latitudinal variability in the seroprevalence of antibodies against Toxoplasma gondii in non-migrant and Arctic migratory geese

Toxoplasma gondii is an intracellular coccidian parasite found worldwide and is known to infect virtually all warm-blooded animals. It requires a cat (family Felidae) to complete its full life cycle. Despite the absence of wild felids on the Arctic archipelago of Svalbard, T. gondii has been found in resident predators such as the arctic fox and polar bear. It has therefore been suggested that T. gondii may enter this ecosystem via migratory birds. The objective of this study was to identify locations where goose populations may become infected with T. gondii, and to investigate the dynamics of T. gondii specific antibodies. Single blood samples of both adults and juveniles were collected from selected goose species (Anser anser, A. brachyrhynchus, Branta canadensis, B. leucopsis) at Arctic brood-rearing areas in Russia and on Svalbard, and temperate wintering grounds in the Netherlands and Denmark (migratory populations) as well as temperate brood-rearing grounds (the Netherlands, non-migratory populations). A modified agglutination test was used on serum, for detection of antibodies against T. gondii. Occasional repeated annual sampling of individual adults was performed to determine the antibody dynamics. Adults were found seropositive at all locations (Arctic and temperate, brood-rearing and wintering grounds) with low seroprevalence in brood-rearing birds on temperate grounds. As no juvenile geese were found seropositive at any brood-rearing location, but nine month old geese were found seropositive during spring migration we conclude that geese, irrespective of species and migration, encounter T. gondii infection in wintering areas. In re-sampled birds on Svalbard significant seroreversion was observed, with 42% of seropositive adults showing no detectable antibodies after 12 months, while the proportion of seroconversion was only 3%. Modelled variation of seroprevalence with field data on antibody longevity and parasite transmission suggests seroprevalence of a population within a range of 5.2–19.9%, in line with measured values. The high occurrence of seroreversion compared to the low occurrence of seroconversion hampers analysis of species- or site-specific patterns, but explains the absence of an increase in seroprevalence with age and the observed variation in antibody titre. These findings imply that even though infection rate is low, adults introduce T. gondii to the high Arctic ecosystem following infection in temperate regions.     

Vitamin C,B5, and B6 contents of segregating potato populations detected by GC‐MS: a method facilitating breeding potatoes with improved vitamin content

Vitamin C, B5, and B6 contents of potato tubers were measured by gas chromatography‐mass spectrometry (GC‐MS). Two diploid potato populations derived from two different crosses were analyzed. Plants were grown at two locations under different environmental conditions. Measurements of vitamin content of tubers showed high variation in both populations. A weak correlation was found between the vitamin concentrations of tubers harvested at the two locations. Correlations between the mean values of vitamins in field‐grown tubers and in different tissues derived from in vitro or greenhouse‐grown potato plants were also determined. A very high correlation between the vitamin content of field‐ and greenhouse‐grown tubers, and between field‐grown tubers and sink leaves of greenhouse‐grown plants was detected. This finding can facilitate breeding by preselection of individuals with improved vitamin content under greenhouse conditions at their early developmental stage.     

Climate change impact predictions on Pinus patula and Pinus tecunumanii populations in Mexico and Central America

Climate change is likely to have a negative impact on natural populations of Pinus patula and Pinus tecunumanii, two globally important tree species in plantation forestry. The objective of this work was to evaluate the impact of climate change on the persistence of the natural populations of these species at their actual locations in order to take appropriate conservation measurements. A common approach to assess the impact of climate change on species natural distributions is climate envelope modeling (CEM). CEMs suggest significant impacts of climate change on the natural distribution of the two pine species, but their predictions contain considerable uncertainty related to the adaptive ability of tree populations to withstand future climate conditions. We assessed the adaptive ability of the two pine species based on the evaluations of provenance trials and used the results of these field trials to validate CEM impact assessment studies on provenance collection sites in the wild. The two pine species performed well in a wide range of climates, including conditions that were recorded by CEM as unsuitable for natural pine occurrence. The climate conditions where the two pine species naturally occur are predicted to become in the future more similar to the present climate of some areas where they are successfully established in field trials. These findings suggest that these pine species are in their natural habitat better adapted to climate change than CEM predicts. For the most vulnerable species, P. tecunumanii, human disturbances such as fragmentation from urbanization and conversion to agriculture that are occurring today are more urgent threats requiring action compared to the threat from climate change.     

A mixed model QTL analysis for a complex cross population consisting of a half diallel of two-way hybrids in Arabidopsis thaliana: analysis of simulated data

To improve QTL detection power for QTL main effects and interactions and QTL mapping resolution, new types of multi-founder crossing populations are created in plants and animals. Some recent examples are complex intercrossed populations in mice and Arabidopsis thaliana. For the latter, a set of eight accessions was intercrossed to produce four two-way hybrids that were subsequently intercrossed again in a half diallel fashion leading to six subpopulations of four-way hybrids, each subpopulation containing 100 individuals. Within each subpopulation, individuals were inbred for four generations via single seed descent. QTL mapping in the complex crosses requires new statistical tools. We present a first sketch of a QTL mapping methodology for the complex cross in Arabidopsis based on mixed model analyses. As experimental data were not yet available, we illustrate our methodology on simulated but realistic data.     

Evaluation of the use of low-density LiDAR data to estimate structural attributes and biomass yield in a short-rotation willow coppice: an example in a field trial

Key message

LiDAR data (low-density data, 0.5 pulses m ^?2 ) represent an excellent management resource as they can be used to estimate forest stand characteristics in short-rotation willow coppice (SRWC) with reasonable accuracy. The technology is also a useful, practical tool for carrying out inventories in these types of stands.

Context

This study evaluated the use of very low-density airborne LiDAR (light detection and ranging) data (0.5 pulses m^?2), which can be accessed free of charge, in an SRWC established in degraded mining land.

Aims

This work aimed to determine the utility of low-density LiDAR data for estimating main forest structural attributes and biomass productivity and for comparing the estimates with field measurements carried out in an SRWC planted in marginal land.

Methods

The SRWC was established following a randomized complete block design with three clones, planted at two densities and with three fertilization levels. Use of parametric (multiple regression) and non-parametric (classification and regression trees, CART) fitting techniques yielded models with good predictive power and reliability. Both fitting methods were used for comprehensive analysis of the data and provide complementary information.

Results

The results of multiple regression analysis indicated close relationships (R_fit ² = 0.63–0.97) between LiDAR-derived metrics and the field measured data for the variables studied (H, D₂₀, D₁₃₀, FW, and DW). High R ² values were obtained for models fitted using the CART technique (R ² = 0.73–0.94).

Conclusion

Low-density LiDAR data can be used to model structural attributes and biomass yield in SRWC with reasonable accuracy. The models developed can be used to improve and optimize follow-up decisions about the management of these crops.

     

Evaluation of tree and stand-level growth models using national forest inventory data

Two models, Carbware (CW) and Growfor (GF), of different resolution and based on different frameworks were evaluated in relation to stand-level forecasts of volume and basal area using Ireland’s National Forest Inventory (NFI) data. CW is a distance-independent single-tree model that is based on diameter increment. GF is a stand-level dynamic empirical model that uses the von Bertalanffy–Richards growth equation in a state-space framework. NFI data were used as input to the models, and each model’s projections were compared to NFI data at the next measurement cycle. The NFI is a permanent sampling system with the objective to assess the composition and extent of the forest estate. A subset of the NFI was used in the study, single-species even-aged plots comprising Sitka spruce and lodgepole pine. The accuracy and performance of the CW and GF models were analysed using residual analysis and standard statistical techniques. Results show that both models require improvement, though the study has raised concerns regarding the suitability of the NFI data for this type of investigation.     

原生质体融合技术改良植病生防木霉菌株

以产孢量大，对苯菌灵有抗性，对潮霉素B敏感的哈茨木霉菌株T9和产孢量少，对潮霉素B有抗性，对苯菌灵敏感的康宁木霉菌株Tk7a为亲本，进行原生质体融合，筛选获得抗最高浓度杀菌剂的融合子。所有融合子的产孢量均比亲本菌株Tk7a大。融合子按照菌落形态的不同分成4组，大部分融合子的几丁质酶、葡聚糖酶和内切葡聚糖酶的活性比亲本菌株高。融合子对棉花猝倒病菌和小麦全蚀病菌的寄生能力基本等同于亲本菌株；融合子对小麦全蚀病的防效比亲本菌株稍好，其刺激麦苗根部生长的能力与亲本菌株相差不大。两个融合子根际竞争能力比亲本菌株T9强，和亲本菌株Tk7a相当。     

Simulation of alternatives for the Dutch Johne's disease certification-and-monitoring program

To identify optimal method(s) for certification and subsequent monitoring of Mycobacterium avium subsp. paratuberculosis (Map)-unsuspected herds, certification-and-monitoring schemes were studied using a stochastic simulation model ("JohneSSim"). JohneSSim simulated the within-herd transmission and economic aspects of Map in closed Dutch dairy herds. The model was validated with field observations on Map-unsuspected herds. The current Dutch certification-and-monitoring schemes were compared with 11 alternative schemes in which individual and pooled fecal culture, ELISA, Johnin-intradermal test and gamma-IFN ELISA were used, varying the test frequency, tested age group and number of tested animals. On reaching the 'Map-free' status with the standard certification scheme, 11% of the simulated herds were not truly Map-free. Therefore, the designation 'Map-free' should be changed into, for instance, 'low-risk Map'. In the most-attractive alternative certification scheme, the 'Map-free' status was reached after four herd examinations (at 2-year intervals) consisting of serial testing of all cattle > or = 2 years of age with a pooled fecal culture and individual fecal culture of positive pools. This scheme resulted in lower total and annual discounted costs and a lower animal-level prevalence at reaching the 'Map-free' status compared to the standard scheme, assuming that there was no new introduction of the infection. Schemes to monitor the 'Map-free' status were compared, assuming that this status was reached with the standard certification scheme. In comparison to the standard monitoring scheme, none of the alternative monitoring schemes resulted in both a lower animal-level prevalence of undetected pre-existing Map infections in closed herds, and lower median annual discounted costs. Results of the model were very sensitive to the assumed sensitivity of the fecal culture test and to management measures that prevent within-herd transmission of Map. If these preventive measures were taken, the probability of undetected Map infections in closed 'Map-free' herds was decreased substantially.