The in vitro response of field strains of sheep blowflies Lucilia sericata and L. cuprina (Calliphoridae) in New Zealand to dicyclanil and triflumuron

AIM: To evaluate the in vitro efficacy of triflumuron and dicyclanil against field strains of Lucilia sericata and L. cuprina in New Zealand to establish whether anecdotal reports of declining protection periods afforded by dips containing these active ingredients had validity.

METHODS: Strains of field-derived blowflies (Lucilia cuprina and L. sericata) were obtained from adult flies from flytraps or larvae from sheep with flystrike submitted from seven regions of the North and two regions of the South Islands of New Zealand. A total of 27 strains of L. sericata and 19 of L. cuprina were established in culture and first instar larvae obtained were exposed in vitro to dilution series of technical-grade dicyclanil (a pyrimidine carbonitrile) and triflumuron (a benzoyl urea). Concentrations lethal to 50% (LC₅₀) and 95% (LC₉₅) of each strain were calculated and tested by probit analysis, with the ratio of LC₅₀ of each strain divided by LC₅₀ of the most susceptible strain (resistance factor) derived in order to facilitate between-strain comparisons of susceptibility.

RESULTS: There was considerable variation between strains of L. sericata larvae in their susceptibility to triflumuron, with those least susceptible originating from the Waikato region. Strains from both Tararua and Manawatu regions were most susceptible and East Coast strains intermediate. All strains of the species tested showed a narrow band of susceptibility to dicyclanil with no regional trends apparent.

CONCLUSIONS: Representative field-strains of sheep blowflies exhibited a range of susceptibilities to both triflumuron and dicyclanil, suggestive of both genetic heterogeneity among fly populations and the spectrum of dip use in their source areas. This means there should be concerns for the long-term benefits of benzoyl urea insecticides for sheep farmers in New Zealand, but not yet for dicyclanil-based formulations.

CLINICAL RELEVANCE: Flystrike is a debilitating and occasionally lethal disease in sheep such that efficacious sheep dips have prophylactic value in reducing the prevalence of the condition.     

伪狂犬病病毒吉林分离株感染BHK-21细胞的超微结构变化

以猪伪狂犬病病毒(PRV)吉林分离株PRV-JL感染体外培养的BHK-21细胞为模型,通过透射电镜对PRV的形态发生学和宿主细胞超微结构的动态变化规律进行研究。结果显示,PRV能导致BHK-21细胞圆缩,并发生细胞融合,形成合胞体;电镜观察到的病毒粒子呈球形或椭圆形,成熟的病毒粒子直径大小为140~210 nm,未成熟病毒粒子直径为90~150 nm,多呈中空状,部分呈致密核芯。病毒吸附于细胞后以膜融合的方式进入细胞,在胞核内复制,装配好的病毒粒子以出芽的方式离开细胞核,获得最初的囊膜,进入胞浆;在胞浆内的病毒粒子又利用高尔基体的膜结构合成第2层囊膜,形成完整的病毒粒子;最后包裹有完整病毒粒子的高尔基囊泡与细胞膜发生融合,将病毒粒子释放到细胞外。感染细胞超微结构变化主要表现为:细胞胞浆空泡增多,内质网扩张,线粒体增生、嵴肿胀、脱落,最后空泡化,整个细胞裂解、破碎。     

Revising Nitrogen Recommendations for Wheat in Response to the Need for Support of Variable-Rate Nitrogen Application

Sampling studies in North Dakota conducted from 1994 to 2003 showed that variable-rate N application could be practically directed with zone soil sampling. Results from variable-rate N studies using zone soil sampling were often less than rewarding due in part to the use of a whole-field predicted yield-based formula for developing the N recommendation in each zone. Nitrogen rate studies on spring wheat and durum were established in 2005 through 2009 with the objective to reexamine N recommendations and construct a new system if necessary. The results of the study and archived wheat N response data showed that the state should be divided into three separate N response regions. Within each region historic yields from low to high productivity were defined. The gross N rate was determined using the return-to-N concept developed in the US corn-belt states but with additional consideration for wheat protein value The gross N rate is then modified by credits for previous crop, soil test N from zone soil sampling, tillage systems, excessive straw from the previous year, relative susceptibility to nitrate leaching or denitrification. Finally, the user is encouraged to use common sense and consider whether particular fields have characteristics that require more or less N fertilizer than suggested by the recommendation formulas.     

A novel hardness-related and starch granule-associated protein marker in wheat: LMW-GS-‘S’

Starch granule (SG)-associated proteins are involved in starch synthesis and the interaction between SGs and the endosperm protein matrix. In this study, SG proteins were sequentially extracted with the chaotropic reagent, urea from 1 M to 4 M, and then profiled using an integrated proteomic approach including one- and two-dimensional electrophoresis, mass spectrometry and antibody-based enzyme-linked immunosorbent assay (ELISA). The results demonstrated that the SG-associated proteins were dominated by granule-bound starch synthase (GBSS), gliadin, low molecular weight glutenin subunits (LMW-GS), serine protease inhibitors, α-amylase inhibitors and puroindolines. A protein with an apparent molecular mass of 50 kDa, expressed in cultivar hard wheat Kukri but not in soft wheat Triller was identified as a novel member of the ‘S’ group of LMW-GS, designated as LMW-GS-‘S’. Further characterization using a broad wheat population revealed that LMW-GS-‘S’ was selectively expressed in hard wheat cultivars while deleted in all soft wheats tested. Its relationship with hardness was confirmed by its expression in tetraploid durum wheats, which are among the hardest wheats around the world. Monoclonal antibody (MAb) F8-14E6 against LMW-GS-‘S’ was developed and used in an ELISA to screen 90 Glu allele-defined doubled haploid Janz/Kukri wheat lines. The allele that encodes LMW-GS-‘S’ was mapped to GluB3h (p < 0.001).     

FIELD TESTING OF A KILLED HAEMOPHILUS PARAHAEMOLYTICUS VACCINE IN PIGS

SUMMARY Piglets immunised with a formalin inactivated alum precipitated vaccine prepared from Haemophilus parahaemolyticus serotype 1 and born to sows treated before farrowing with an alum hydroxide adjuvant vaccine had a lower mortality rate and death rate from pleuropneumonia than control piglets.