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91.
Crop wild relatives are invaluable sources of novel genes for crop improvement and adaptation to changing environments. We assessed phylogenetic relationships among 29 Linum accessions representing 16 species, including cultivated flax and its progenitor pale flax, based on four non-coding regions of chloroplast DNA sequences. We obtained a cpDNA network showing that these 16 Linum species are appropriately connected based on previously defined taxonomic sections; these connections reflect the same evolutionary pathways as determined from earlier morphological and cytological data. These relationships also support an earlier hypothesis that cultivated flax is probably descended from a single domestication of pale flax plants, apparently for oil usage. The detailed species network not only is significant for understanding evolutionary relationships of Linum species, but also useful for classifying exotic gene pools of cultivated flax as a part of the ongoing exploration of new genetic diversity for flax improvement.  相似文献   
92.

Introduction   

Scots pine populations in the SE “Sistema Ibérico” range suffered a severe defoliation in the S face of the crown in isolated trees of thinned stands. This process was detected at the end of the winter 2001–2002.  相似文献   
93.
We present novel dynamic mixture models for the monitoring of bumblebee populations on an unprecedented geographical scale, motivated by the UK citizen science scheme BeeWalk. The models allow us for the first time to estimate bumblebee phenology and within-season productivity, defined as the number of individuals in each caste per colony in the population in that year, from citizen science data. All of these parameters are estimated separately for each caste, giving a means of considerable ecological detail in examining temporal changes in the complex life cycle of a social insect in the wild. Due to the dynamic nature of the models, we are able to produce population trends for a number of UK bumblebee species using the available time-series. Via an additional simulation exercise, we show the extent to which useful information will increase if the survey continues, and expands in scale, as expected. Bumblebees are extraordinarily important components of the ecosystem, providing pollination services of vast economic impact and functioning as indicator species for changes in climate or land use. Our results demonstrate the changes in both phenology and productivity between years and provide an invaluable tool for monitoring bumblebee populations, many of which are in decline, in the UK and around the world. Supplementary materials accompanying this paper appear online.  相似文献   
94.
Fundulus heteroclitus and F. grandis are resident salt marsh fishes that overlap in distribution over a narrow range in northeastern Florida. The objective of the present study was to examine whether the limits of the species’ ranges could be explained by differences in thermal tolerance. Two populations of each species were collected and then spawned in the laboratory, and 9-day-old larvae were used for critical thermal maxima trials. Mean LOE temperatures of larvae ranged from 43.04 to 43.65°C and showed little difference between species. Therefore, differences in high temperatures experienced cannot account for the differences of the distributions of the two species. Condition-specific competition may play a greater role in determining the observed range of the two species.  相似文献   
95.

Context   

Rotation length is known to affect timber quality in many plantation species, but its effect on the properties of Sitka spruce (Picea sitchensis) structural timber has not been quantified.  相似文献   
96.
Here Fusarium oxysporum was killed in exudates obtained from soil biologically disinfested with ethanol, indicating that physical interaction with soil microorganisms was not essential. Because acetic acid was confirmed to accumulated during the treatment, we evaluated the effect of acetic acid amendment against the pathogen in plastic containers. A drop in the soil redox potential seemed to be correlated with the fungicidal efficacy of acetic acid. Under reductive soil conditions, metal ions such as Mn2+ and Fe2+ formed, and the pathogen was effectively suppressed in Mn2+ and Fe2+ solution. Therefore, Fe2+ and Mn2+ may be the agents that induce suppression of the pathogen during biological soil disinfestation.  相似文献   
97.
As an alternative to ground-cover data collection by conventional and expensive sampling techniques, we compared measurements obtained from very large scale aerial (VLSA) imagery for calibrating moderate resolution Landsat data. Using a grid-based sampling scheme, 162 VLSA images were acquired at 100 m above ground level. The percent vegetation cover in each photo was derived using SamplePoint (a manual inventory method) and VegMeasure (a reflectance based, automated method). Approximately two-thirds of the VLSA images were used for calibrating Landsat data while the remainder was used for validation. Regression models with Landsat bands accounted for 55% of the VegMeasure-based measurements of vegetation, whereas models that included both Landsat bands and elevation data accounted for 67%. The relationship between the Landsat bands and the percent vegetation cover measured by SamplePoint was lower (R 2 = 20%), highlighting the differences between the inventory and reflectance based protocols. Results from the model validation indicated that the model’s predictive power was lower when the vegetation cover was either <20% or >55%. Additional work is needed in these ecosystems to improve the calibration techniques for sites with low and high vegetation cover; however, these results demonstrate the VLSA imagery could be used for calibrating Landsat data and deriving rangeland vegetation cover. By adopting such methodologies the US Federal land management agencies can increase the efficiency of the monitoring programs in Wyoming and in other western states of the US. Mention of trade names is for information only and does not imply endorsement by USDA over comparable products or services.  相似文献   
98.
The objective of this study was to identify molecular markers linked to fruit-related traits in the tomato subjected to high temperatures. In total, 160 F2 plants derived from a cross between a heat-tolerant breeding line, CL5915-93D4-1-0-3 (Solanum esculentum), and a heat-sensitive wild accession, L4422 (S. pimpinellifolium), were grown in a greenhouse. Six traits including fruit number, fruit weight, brix, seed number, fruit setting, and flower number were scored. The distributions of fruit number, fruit set, flower number, and seed number were skewed towards heat susceptibility which is known to be characteristic of L4422. Polymorphic bands were generated by PCR-derived methods of RAPD, ISSR and AFLP Polymorphism, the segregation ratio, and distribution over the genome of the above 3 markers were compared. Ten linkage groups, ranging 20.6–151.6 cM in size, were constructed with 62 informative markers spanning a total of 776.3 cM. Fruit-related quantitative trait loci (QTLs) were non-randomly distributed in the tomato genome. For the 6 traits investigated, 21 QTLs were dispersed on linkage groups 2–5. The genetic effects of the various QTLs were differently exhibited, in our study we have respectively found from 10.5% to 30.2% of the variation explained by the QTL for flower number (FRN4) and brix (BX2). Thirteen QTL-mapped markers were unique to 1 trait, and 4 markers were linked to more than 1 trait. Among them, QTLs linked to the I868-470 marker had effects on fruit weight and brix, and a significant positive correlation between these 2 traits was noted (r = 0.35, P < 0.05). Thus, the I868-470 marker may have the potential for simultaneous selection of high fruit weight and brix. These markers also allowed us to align genome linkage maps across distantly related species and to reveal the co-localization between these QTLs and major genes.  相似文献   
99.
In the initial phase of a national project to map clay, sand and soil organic matter (SOM) content in arable topsoil in Sweden, a study area in south-west Sweden comprising about 100 000 ha of arable land was assessed. Models were created for texture, SOM and two estimated variables for lime requirement determination (target pH and buffering capacity), using a data mining method (multivariate adaptive regression splines). Two existing reference soil datasets were used: a grid dataset and a dataset created for individual farms. The predictor data were of three types: airborne gamma-ray spectrometry data, digital elevation from airborne laser scanning, and legacy data on Quaternary geology. Validations were designed to suit applicability assessments of prediction maps for precision agriculture. The predictor data proved applicable for regional mapping of topsoil texture at 50 × 50 m2 spatial resolution (root mean square error: clay = 6.5 %; sand = 13.2 %). A novel modelling strategy, ‘Farm Interactive’, in which soil analysis data for individual farms were added to the regional data, and given extra weight, improved the map locally. SOM models were less satisfactory. Variable-rate application files for liming created from derived digital soil maps and locally interpolated soil data were compared with ‘ground truth’ maps created by proximal sensors on one test farm. The Farm Interactive methodology generated the best predictions and was deemed suitable for adaptation of regional digital soil maps for precision agricultural purposes.  相似文献   
100.
This paper examines the occurrence and impact of gender discrimination in access to production resources on the income, productivity, and technical efficiency of farmers. Through an empirical investigation of farmers from Koussin-Lélé, a semi-collective irrigated rice scheme in central Benin, we find that female rice farmers are particularly discriminated against with regard to scheme membership and access to land and equipment, resulting in significant negative impacts on their productivity and income. Although women have lower productivity, they are as technically efficient as men. The findings suggest that there is considerable scope for improving the productivity of women through increasing their access to production resources.  相似文献   
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