Tissue culture and the propagation and genetic improvement of conifers: problems and possibilities

The utilization of tissue culture in the propagation and genetic improvement of conifers holds promise of many benefits including faster multiplication of selected genotypes, faster development of improved genotypes and the transfer of genes between non-fertile parents. However, many of the techniques required for the realization of this potential remain to be developed. Furthermore, genetic differentiation of cells in culture creates uncertainty as to the fidelity of reproduction by micropropagation. Aspects of the problem of nuclear DNA variation during reproduction by tissue culture are reviewed with particular reference to the genus Pinus.     

Mechanical evaluation of two loop tensioning methods for crimp clamp extracapsular stabilization of the cranial cruciate ligament-deficient canine stifle

OBJECTIVES: To describe a method of tightening nylon loops secured with a crimping system for extracapsular fabello-tibial stabilization of the cranial cruciate ligament-deficient stifle and to compare this with a method using a commercially available tensioning device.STUDY DESIGN: In vitro mechanical testing.METHODS: Fourteen standardized nylon loops were tensioned using a tensioning device and secured with crimp clamps. Another 14 loops were tightened by partially securing the crimp clamp, followed by tightening of the loop by hand, before definitively securing the crimp clamp. Loops were loaded to failure in a materials testing machine.RESULTS: Mean ultimate loads for instrument-tightened and hand-tightened loops were 383.7 and 371.4 N, respectively. Mean stiffness values for instrument-tightened and hand-tightened loops were 59.7 and 59.3 N/mm, respectively. These differences were not significant.CONCLUSIONS: The hand tightening method does not affect the mechanical properties of the loop.CLINICAL RELEVANCE: The hand tightening method described is a valuable technique for unassisted surgeons without access to tensioning devices.     

Color and albedo heterogeneity of Vesta from Dawn

Multispectral images (0.44 to 0.98 μm) of asteroid (4) Vesta obtained by the Dawn Framing Cameras reveal global color variations that uncover and help understand the north-south hemispherical dichotomy. The signature of deep lithologies excavated during the formation of the Rheasilvia basin on the south pole has been preserved on the surface. Color variations (band depth, spectral slope, and eucrite-diogenite abundance) clearly correlate with distinct compositional units. Vesta displays the greatest variation of geometric albedo (0.10 to 0.67) of any asteroid yet observed. Four distinct color units are recognized that chronicle processes--including impact excavation, mass wasting, and space weathering--that shaped the asteroid's surface. Vesta's color and photometric diversity are indicative of its status as a preserved, differentiated protoplanet.     

Ultrastrong coupling of the cyclotron transition of a 2D electron gas to a THz metamaterial

Artificial cavity photon resonators with ultrastrong light-matter interactions are attracting interest both in semiconductor and superconducting systems because of the possibility of manipulating the cavity quantum electrodynamic ground state with controllable physical properties. We report here experiments showing ultrastrong light-matter coupling in a terahertz (THz) metamaterial where the cyclotron transition of a high-mobility two-dimensional electron gas (2DEG) is coupled to the photonic modes of an array of electronic split-ring resonators. We observe a normalized coupling ratio, Ω/ω(c) = 0.58, between the vacuum Rabi frequency, ?, and the cyclotron frequency, ω(c). Our system appears to be scalable in frequency and could be brought to the microwave spectral range with the potential of strongly controlling the magnetotransport properties of a high-mobility 2DEG.     

Consequences of Treating Wyoming Big Sagebrush to Enhance Wildlife Habitats

Sagebrush (Artemisia L.) taxa historically functioned as the keystone species on 1 090 000 km² of rangeland across the western United States, and Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle and Young) is or was dominant on a substantial amount of this landscape. Wyoming big sagebrush provides habitat for numerous wildlife species. Nevertheless, Wyoming big sagebrush communities are commonly manipulated to decrease shrub cover and density and increase the productivity and diversity of herbaceous plants. We examined relationships between management-directed changes in Wyoming big sagebrush and greater sage-grouse (Centrocercus urophasianus), elk (Cervus elaphus), pronghorn (Antilocapra americana), and mule deer (Odocoileus hemionus), species commonly associated with these ecosystems. We focused on herbicide applications, mechanical treatments, and prescribed burning, because they are commonly applied to large areas in big sagebrush communities, often with the goal to improve wildlife habitats. Specifically, our objective was to identify treatments that either enhance or imperil sagebrush habitats for these wildlife species. The preponderance of literature indicates that habitat management programs that emphasize treating Wyoming big sagebrush are not supported with respect to positive responses by sage-grouse habitats or populations. There is less empirical information on ungulate habitat response to Wyoming big sagebrush treatments, but the value of sagebrush as cover and food to these species is clearly documented. A few studies suggest small-scale treatments (≤ 60-m width) in mountain big sagebrush (Artemisia tridentata ssp. vaseyana [Rydb.] Beetle) may create attractive foraging conditions for brooding sage-grouse, but these may have little relevance to Wyoming big sagebrush. Recommendations or management programs that emphasize treatments to reduce Wyoming big sagebrush could lead to declines of wildlife species. More research is needed to evaluate the response of sagebrush wildlife habitats and populations to treatments, and until that time, managers should refrain from applying them in Wyoming big sagebrush communities.     

Do Introduced Grasses Improve Forage Production on the Northern Mixed Prairie

Relative benefit of introducing forage species to the Northern Great Plains have been examined with contradictory conclusions. In most cases, studies were either confounded by time of establishment or treatments were not randomized and lacked independence. We examined aboveground net primary production (ANPP) in northern mixed prairie using a randomized complete block design with four treatments: crested wheatgrass (Agropyron cristatum [L.] Gaertn.), Russian wildrye (Psathyrostachys juncea [Fisch.] Nevski), a native control that was not harvested, and a harvested native. The experiment was conducted in a Stipa–Agropyron–Bouteloua site and a Stipa–Bouteloua site over 13 yr and 12 yr, respectively. The data were analyzed by sampling period (Stipa–Agropyron–Bouteloua: 1, 1994 to 1997; 2, 1998 to 2001; 3, 2002 to 2006; and Stipa–Bouteloua: 1, 1995 to 1998; 2, 1999 to 2002; 3, 2003 to 2006). ANPP among treatments was influenced (P < 0.05) by site and its interaction with treatment and sampling period (1 to 3). ANPP from the native-control, harvested-native, crested wheatgrass, and Russian wildrye treatments was 220.9, 183.9, 300.8, and 189.6 g · m^–2 (SEM = 11.2), respectively, in the Stipa–Agropyron–Bouteloua site and 122.9, 98.2, 216.3, and 115.9 g · m^–2 (SEM = 12.0), respectively, in the Stipa–Bouteloua site. Mean ANPP (SEM) within each sampling period (1 to 3) was 186.4 (9.1), 135.4 (5.8), and 263.9 (8.8) g · m^–2 in the Stipa–Agropyron–Bouteloua site, respectively, and 124.5 (6.4), 138.6 (6.1), and 151.3 (10.5) g · m^–2 in the Stipa–Bouteloua site, respectively. Russian wildrye in the Stipa–Bouteloua site and crested wheatgrass in both sites was relatively more productive in the first period after establishment than in subsequent years. The study confirms the relative ANPP advantage of crested wheatgrass over native on the Stipa–Bouteloua site but not on the Stipa–Agropyron–Bouteloua site, whereas Russian wildrye exhibited no ANPP advantage over the native on either site.     

Effect of the spray application technique on the deposition of entomopathogenic nematodes in vegetables

BACKGROUND: The present study compared entomopathogenic nematode delivery at the base of savoy cabbage and cauliflower, at the lower side of savoy cabbage and cauliflower leaves and in leek stems and the ground deposition using a five‐nozzle spray boom equipped with an ISO 08 flat fan, an air induction flat fan and Twinjet spray nozzles. Additionally, an air support system and a row application system were evaluated. RESULTS: Approximately 40% of the applied nematodes did not reach the foot of the cabbage plants. The use of an air support system or a row application system improved nematode deposition at the savoy cabbage base. Relative nematode deposition on the lower side of savoy cabbage leaves was 27.20%, while only 2.64% of the applied nematodes reached the lower side of cauliflower leaves. After spraying leek with a standard boom, a low relative nematode deposition (26.64%) was measured in the leek stem. Nozzle type affected the distribution of nematodes in droplet spots. CONCLUSION: Nozzle type has a minor effect on the number of entomopathogenic nematodes delivered on difficult‐to‐reach targets. The use of modified spray application techniques directing the spray to the target site are necessary to increase the chances of contact of entomopathogenic nematodes with their target. Copyright © 2011 Society of Chemical Industry     

Effects of stocking and nitrogen fertilization rates on steers grazing dallisgrass-dominated pasture

To compare the performance of steer calves managed under different stocking rates (SR; 3.7, 6.2, 8.6, and 11.1 steers/ha for 140 d; chi(I1)) and N fertilization rates (112, 224, and 336 kg of N/ha; chi(I2)) in May 1996, 1997, and 1998, 72 steer calves (BW = 231 +/- 2.5 kg) were assigned randomly to one of 12 0.81-ha dallisgrass (51%)/common bermudagrass (32%) pastures. One-third of the fertilizer was applied in the form of ammonium nitrate in May, June, and August to achieve the prescribed totals. Treatments were separated using a polynomial regression equation: gammai = beta0 + beta1chi(I1) + beta2chi(I2) + beta(11)chi2(I1) + beta(12)chi2(I2) + beta(12)chi(i1)chi(i2) + epsilonI, with years as replicates. Within the range of the data, ADG and BW gain per steer were greatest at a stocking rate of 3.7 steers/ha and 336 kg/ha of N. Body weight gain per hectare peaked at 701 kg when cattle were stocked at 8.9 steers/ha and the pasture was fertilized with 336 kg/ha of N. The least cost of production was at a stocking rate of 3.7 steers/ha, with 112 kg/ha of fertilizer N applied, and the greatest cost of production was at a stocking rate of 11.1 steers/ha with 336 kg/ha of fertilizer N applied. Fertilization at 336 kg/ha of N produced the most profitable stocking rate at 7.3 steers/ha and returned 355.64 dollars. The optimal stocking rate for net return was 79, 81, and 82% of that for maximum BW gain per hectare for 112, 224, and 336 kg/ha of N, respectively. Under the assumptions made in the financial analysis, these data show that the economically optimal carrying capacity of similar pastures can be increased with N fertilizer up to at least 336 kg/ha annually.     

Evaluation of ELISA for detection of Trichinella antibodies in muscle juice samples of naturally infected pigs

The performance characteristics of an ELISA test for trichinellosis in pigs applied to muscle juice was assessed using 314 samples collected from pigs located in endemic areas of Croatia. Peptic digestion was used as the reference method. The diagnostic accuracy of the two compared dilutions (1:10 and 1:100) was considered to be high because the area under the curve (AUC) index was 0.922 and 0.920 for each dilution, respectively. In this study the two graph-receiver operating characteristic (TG-ROC) analysis was used as a tool for selecting cut-off points. Sensitivity, specificity, likelihood ratios, efficiency and Youden's index were used as indices of test accuracy. The cut-off values that minimize overall misclassification cost under an assumption of 3% prevalence were calculated. Our results indicate that the ELISA applied to muscle juice is a highly accurate test and can be adapted to process a large number of samples.