A field study of reproductive performance and productivity of Pelibuey ewes in Southeastern Mexico

The objective was to evaluate the reproductive performance and productivity of Pelibuey ewes in two flocks in Southeastern Mexico. Animals grazed on irrigated star grass (Cynodon plectostachyus). In flock 1, lambs grazed with their mothers from 7 to 70 days of age (weaning age), whereas in flock 2, they were confined and offered chopped grass, a commercial concentrated and managed under restricted suckling until weaning at 60 days of age.. The statistical model included the fixed effects of flock, year and season of lambing, parity number, litter size at weaning, first order interactions and the random effects of ewe and the error term. The means ± SD for age at first lambing, prolificacy, lambing interval (LI), weaning weight, and productivity were 477?±?85.5 days, 1.41?±?0.51 lambs, 255.9?±?51.8 days, 16.5?±?4 kg, and 18.1?±?4.42 kg of lamb weaned, respectively. Repeatability estimates for the latter four traits were 0.09, 0.07, 0.11, and 0.13, respectively. All main effects in the models were significant (P?<?0.001), except for year on LI. Prolificacy and productivity increased with parity number. The shortest LI was in the rainy season. Ewes with two or three lambs produced 8 and 14 kg of lamb more at weaning than single lamb ewes. In conclusion, reproductive performance and productivity could be improved, and the low repeatability estimates suggest that management should be used in a short term rather than genetic approaches.     

Effect of treatment on the dynamics of circulating hypodermin C in cattle naturally infested with Hypoderma lineatum (Diptera: Oestridae)

An antigen capture ELISA, using a murine monoclonal antibody recognising recombinant hypodermin C (rHyC), was used to evaluate the influence of early treatment with eprinomectin (Eprinex) or fenthion (Spotton) on the kinetics of circulating hypodermin C in calves naturally infested with Hypoderma lineatum. No viable larvae were collected from treated animals, whereas a variable number of warbles were found in control animals. Treatment provoked a decrease in circulating HyC levels that was significant 9 days post-treatment (p.t.). Circulating antigen levels in the treated cattle remained detectable for approximately 99 days p.t. In contrast, control animals had no detectable antigen at 64 days p.t., 42 days earlier than in the treated animals. These results suggest that larvae were either gradually killed, resulting in slow release of antigen or they were encapsulated, leading to the slow liberation of antigen. Kinetics of circulating HyC did not differ among the two insecticide treatments. Antibodies persisted, in all groups, throughout the 120-day study. These results suggest that the antigen capture ELISA will be useful as a technique for detecting successful treatment of cattle grub infestations and for the detection of new infestations in previously infested cattle.     

Marker‐trait association analysis for postharvest needle retention/abscission in balsam fir (Abies balsamea)

Balsam fir the principal tree species of the Christmas tree industry, is a major export commodity of Atlantic Canada region. However, postharvest needle abscission poses a main concern leading to low consumer satisfaction and a shift in preference towards artificial trees. The search for diverse balsam fir lines with high needle retention is very crucial for quality improvement programmes. In this regard, a panel of 75 balsam fir genotypes exhibiting diversity for needle retention traits were randomly selected from a set of 220 genotypes evaluated for needle retention characteristics for two consecutive years (2012 and 2013) and genotyped with 41 bi‐allelic single nucleotide polymorphism (SNP)/insertion/deletion markers. The cluster analysis and population structure identified four and seven subpopulations. We observed an SNP marker with significant association (p < 0.05) with the needle retention/abscission trait by using general linear model and mixed linear model approaches. The present study lays the foundation for analysing the genetic mechanisms underlying needle retention/abscission, as well as the use of molecular markers to target specific traits in balsam fir.     

Changes in phenolic composition induced by Pseudomonas savastanoi pv. Savastanoi infection in olive tree: presence of large amounts of verbascoside in nodules of tuberculosis disease

A study was carried out to determine the changes in phenolic composition induced by tuberculosis infection in olive trees. Four ethanolic extracts were compared: olive leaf from shoots affected by Pseudomonas savastanoi pv. Savastanoi, nodules induced by this bacteria, leaf from healthy (asymptomatic) shoots, and shoots. Among the differences found, the presence of a phenolic compound in nodules was significant in much larger quantities than in leaf or shoots. Mass spectrometric analysis showed this compound to be verbascoside. The enhancement of its biosynthesis could be related to the defense mechanisms of the tree in the nodules induced by P. savastanoi and suggests the possibility of exploration of natural and biotechnological sources of this compound.     

Direct link between mhc polymorphism,T cell avidity,and diversity in immune defense

Major histocompatibility complex (mhc)-encoded molecules govern immune responses by presenting antigenic peptides to T cells. The extensive polymorphism of genes encoding these molecules is believed to enhance immune defense by broadening the array of antigenic peptides available for T cell recognition, but direct evidence supporting the importance of this mechanism in combating pathogens is limited. Here we link mhc polymorphism-driven diversification of the cytotoxic T lymphocyte (CTL) repertoire to the generation of high-avidity, protective antiviral T cells and to superior antiviral defense. Thus, much of the beneficial effect of the mhc polymorphism in immune defense may be due to its critical influence on the properties of the selected CTL repertoire.     

Dynamical response of the tropical Pacific Ocean to solar forcing during the early Holocene

We present a high-resolution magnesium/calcium proxy record of Holocene sea surface temperature (SST) from off the west coast of Baja California Sur, Mexico, a region where interannual SST variability is dominated today by the influence of the El Ni?o-Southern Oscillation (ENSO). Temperatures were lowest during the early to middle Holocene, consistent with documented eastern equatorial Pacific cooling and numerical model simulations of orbital forcing into a La Ni?a-like state at that time. The early Holocene SSTs were also characterized by millennial-scale fluctuations that correlate with cosmogenic nuclide proxies of solar variability, with inferred solar minima corresponding to El Ni?o-like (warm) conditions, in apparent agreement with the theoretical "ocean dynamical thermostat" response of ENSO to exogenous radiative forcing.     

人工育苗条件下大黄鱼仔、稚、幼鱼的摄食与生长

在人工育苗条件下,对0到40日龄大黄鱼(Pseudosciaenacrocea,Richardson)仔、稚鱼及早期幼鱼的摄食习性与生长特性进行研究。水温(24±1)℃时,孵化后0～5d属于仔鱼期,6～20d为稚鱼期,第21天起转为幼鱼期。大黄鱼仔鱼孵化3d后开口摄食;开口时平均口径为240μm,40日龄达2480μm;口径的大小变化与日龄的关系是:y=0.2327e0.0682x,R2=0.9492。试验用的生物饵料与实际生产一致,包括轮虫、丰年虫无节幼体、活桡足类和冷藏桡足类。不同生长期的大黄鱼鱼苗的摄食活动具有明显的昼夜节律:在1昼夜(24h)中,仔鱼仅在18:00左右出现1个摄食高峰,而稚鱼和幼鱼除了在18:00左右出现1个显著的摄食高峰外,在10:00左右还有1个相对小的摄食高峰。仔、稚、幼鱼夜间基本不摄食。大黄鱼鱼苗具有较高的摄食率和饱食率,随着生长而迅速升高。仔、稚、幼鱼的生长速度具有明显的阶段性,1～2日龄仔鱼生长较快,5～9日龄生长减慢,21～30日龄生长加快,31～40日龄生长减慢。这与鱼苗的食物转换和饵料生物的营养变化有关:5～9日龄生长减慢是由于鱼苗由混合营养转变为外源性营养所致;31～40日龄生长减慢是因为冷藏桡足类的营养价值较低。鱼体全长与日龄的关系式为y=3.2552e0.0472x,R2=0.9710;体长与日龄的关系式为y=3.3205e0.0374x,R2=0.9777;     

Effects of tillage and nitrogen management on soil chemical and physical properties after 23 years of continuous sorghum

Long-term tillage and nitrogen (N) management practices can have a profound impact on soil properties and nutrient availability. A great deal of research evaluating tillage and N applications on soil chemical properties has been conducted with continuous corn (Zea Mays L.) throughout the Midwest, but not on continuous grain sorghum (Sorghum bicolor (L.) Moench). The objective of this experiment was to examine the long-term effects of tillage and nitrogen applications on soil physical and chemical properties at different depths after 23 years of continuous sorghum under no-till (NT) and conventional till (CT) (fall chisel-field cultivation prior to planting) systems. Ammonium nitrate (AN), urea, and a slow release form of urea were surface broadcast at rates of 34, 67, and 135 kg N ha⁻¹. Soil samples were taken to a depth of 15 cm and separated into 2.5 cm increments. As a result of lime applied to the soil surface, soil pH in the NT and CT plots decreased with depth, ranging from 6.9 to 5.7 in the NT plots and from 6.5 to 5.9 in the CT plots. Bray-1 extractable P and NH₄OAc extractable K was 20 and 49 mg kg⁻¹ higher, respectively, in the surface 2.5 cm of NT compared to CT. Extractable Ca was not greatly influenced by tillage but extractable Mg was higher for CT compared to NT below 2.5 cm. Organic carbon (OC) under NT was significantly higher in the surface 7.5 cm of soil compared to CT. Averaged across N rates, NT had 2.7 Mg ha⁻¹ more C than CT in the surface 7.5 cm of soil. Bulk density (Δ_b) of the CT was lower at 1.07 g cm⁻³ while Δ_b of NT plots was 1.13 g cm⁻³. This study demonstrated the effect tillage has on the distribution and concentration of certain chemical soil properties.     

O-glycosylated cell wall proteins are essential in root hair growth

Root hairs are single cells that develop by tip growth and are specialized in the absorption of nutrients. Their cell walls are composed of polysaccharides and hydroxyproline-rich glycoproteins (HRGPs) that include extensins (EXTs) and arabinogalactan-proteins (AGPs). Proline hydroxylation, an early posttranslational modification of HRGPs that is catalyzed by prolyl 4-hydroxylases (P4Hs), defines the subsequent O-glycosylation sites in EXTs (which are mainly arabinosylated) and AGPs (which are mainly arabinogalactosylated). We explored the biological function of P4Hs, arabinosyltransferases, and EXTs in root hair cell growth. Biochemical inhibition or genetic disruption resulted in the blockage of polarized growth in root hairs and reduced arabinosylation of EXTs. Our results demonstrate that correct O-glycosylation on EXTs is essential for cell-wall self-assembly and, hence, root hair elongation in Arabidopsis thaliana.     

烟草苗床上的甲基溴替代技术研究

采用田间试验方法,研究了在烟草苗床上的甲基溴替代技术。结果表明,与甲基溴相比,浮盘育苗法可生产整齐、高质量的烟苗;浮盘育苗法无须抗旱、除草、假植,可直接移栽到大田,节省大量劳力;浮盘法不施用杀虫剂、除草剂,减少了农药的污染和对环境的破坏,有利于提高烟草的品质和对生态环境的保护;浮盘法单位面积能生产更多的烟苗。因此,浮盘育苗法具有显著的经济效益和环境生态效益,在烟草苗床上是一项可持续发展的甲基溴替代技术。