跑道式循环水臭氧处理实验

在230升的跑道式循环海水中,用于养殖温水性海水鱼——红拟石首鱼(Sciaenopsocellatus)鱼苗和方氏对虾(Penaeus vannamei)稚虾,辅助臭氧处理作用,分别在3小时、6小时和24小时观测鱼、虾对水中残留臭氧的忍耐力。实验证明,虾能够忍受残留臭氧浓度超过2.5mg/L达3小时,浓度为1.0mg/L时。达24小时;鱼种可以忍受臭氧浓度高于0.1mg/L达24小时而不损伤其鳃细胞膜     

Occurrence, Distribution, and Polymerase Chain Reaction-Based Detection of Resistance to Sterol Demethylation Inhibitor Fungicides in Populations of Blumeriella jaapii in Michigan

ABSTRACT The intensive use of site-specific fungicides in agricultural production provides a potent selective mechanism for increasing the frequency of fungicide-resistant isolates in pathogen populations. Practical resistance occurs when the frequency and levels of resistance are great enough to limit the effectiveness of disease control in the field. Cherry leaf spot (CLS), caused by the fungus Blumeriella jaapii, is a major disease of cherry trees in the Great Lakes region. The site-specific sterol demethylation inhibitor fungicides (DMIs) have been used extensively in the region. In 2002, CLS control failed in a Michigan orchard that had used the DMI fenbuconazole exclusively for 8 years. That control failure and our observations from around the state suggested that practical resistance had developed in B. jaapii. Field trial data covering 1989 to 2005 for the DMIs fenbuconazole and tebuconazole supported observations of reduced efficacy of DMIs for controlling CLS. To verify the occurrence of fungicide-resistant B. jaapii, monoconidial isolates were collected in two surveys and tested using a fungicide-amended medium. In one survey, 137 isolates from sites with different DMI histories (no known history, mixed or alternated with other fungicides, and exclusive use) were tested against 12 concentrations of fenbuconazole, tebuconazole, myclobutanil, and fenarimol. Isolates from sites with no prior DMI use were DMI sensitive (DMI(S) = no colony growth at 0.2 mug/ml a.i.) whereas the isolates from the site with prior exclusive use showed growth at DMI concentrations 3 to >100 times higher, and were rated as DMI resistant (DMI(R)). A second survey examined 1,530 monoconidial isolates, including 1,143 from 62 orchard sites in Michigan, where DMIs had been used to control CLS. Resistance to fenbuconazole was detected in 99.7% of the orchard isolates. All isolates from wild cherry trees were sensitive and isolates from feral and dooryard trees showed a range of sensitivities. A polymerase chain reaction (PCR)-based detection method for identifying B. jaapii and DMI(R) was developed and tested. The species-specific primer pair (Bj-F and Bj-R) based on introns in the CYP51 gene of B. jaapii, and the DMI(R)-specific primer pair (DMI-R-Bj-F and DMI-R-Bj-R) based on an insert found upstream of CYP51 in all DMI(R) isolates, provided an accurate and rapid method for detecting DMI(R) B. jaapii. The PCR-based identification method will facilitate timely decision making and continued monitoring of DMI(R) subpopulations in response to management programs.     

Individual-based approach to modeling hyphal growth of a biocontrol fungus in soil

ABSTRACT Fungi in soil perform beneficial roles that include biological control of soilborne plant pathogens. However, relatively little predictive information is available about the growth and activity of fungal hyphae in soil habitats. A stochastic computer simulation model ("Fungmod") was developed to predict hyphal growth of the biocontrol fungus Trichoderma harzianum ThzID1 in soil. The model simulates a fungal colony as a population of spatially referenced hyphal segments, and is individual-based, in that records of spatial location and branching hierarchy are maintained for individual hyphal nodes. In this way, the entire spatial structure of the fungal colony (hyphal network) can be explicitly reconstructed at any point in time. Also, the soil habitat is modeled as a population of spatially referenced 1-mm(3) soil cells, allowing for the simulation of a spatially heterogeneous environment. Initial hyphal growth parameters were derived from previously published results, and the model was tested against new data derived from image analysis of hyphal biomass accumulation in soil. The ability to predict fungal growth in natural habitats will help to improve the predictability of successful myco-parasitic events in biological control systems.     

Genome expansion and gene loss in powdery mildew fungi reveal tradeoffs in extreme parasitism

Powdery mildews are phytopathogens whose growth and reproduction are entirely dependent on living plant cells. The molecular basis of this life-style, obligate biotrophy, remains unknown. We present the genome analysis of barley powdery mildew, Blumeria graminis f.sp. hordei (Blumeria), as well as a comparison with the analysis of two powdery mildews pathogenic on dicotyledonous plants. These genomes display massive retrotransposon proliferation, genome-size expansion, and gene losses. The missing genes encode enzymes of primary and secondary metabolism, carbohydrate-active enzymes, and transporters, probably reflecting their redundancy in an exclusively biotrophic life-style. Among the 248 candidate effectors of pathogenesis identified in the Blumeria genome, very few (less than 10) define a core set conserved in all three mildews, suggesting that most effectors represent species-specific adaptations.     

Vivax-type malaria parasite of macaques transmissible to man

Transmission of Plasmodium cynomolgi bastianellii from rhesus monkeys to two human subjects by Anopheles freeborni and the occurrence of attacks of malaria in two other laboratory workers not exposed to human malaria suggests the existence of an animal reservoir of infection complicating malaria control and eradication.     

Duration of lactation,endocrine and metabolic state,and fertility of primiparous sows

The objectives of this study were to determine factors affecting the reproductive performance of primiparous sows early weaned (EW; n = 35) at d 14 or conventionally weaned (CW; n = 35) at d 24 of lactation. Sow BW and backfat were recorded at farrowing, weekly until weaning, and at standing heat. Feed intake was controlled throughout lactation to standardize nutritional effects on subsequent reproductive performance. Litter size was standardized across treatments within 48 h after farrowing, and litter weight was recorded until weaning. In subsets of sows, blood samples were collected from 10 h before to 10 h after weaning, and then every 6 h until ovulation. Sows were heat checked twice daily and bred at 24-h intervals during standing heat using pooled semen. Ultrasonography every 6 h determined time of ovulation. Sows were either slaughtered within 24 h after ovulation to assess ovulation rate, fertilization rate, and embryonic development in vitro, or at d 28 of gestation to determine ovulation rate and embryonic survival. Compared with CW sows, EW sows had more backfat at weaning (15.9 +/- 0.5 vs. 14.7 +/- 0.5 mm; P < 0.001). Also, CW sows tended to lose more BW and to have lower IGF-I concentrations, indicating poorer body condition. Duration of lactation did not affect ovulation rate (EW = 17.6 +/- 0.7; CW = 18.7 +/- 0.6), fertilization rate (EW = 96.0 +/- 2.2; CW = 88.2 +/- 4.7%), or embryo survival to d 28 (EW = 62.5 +/- 4.5; CW = 63.1 +/- 5.0%). There was a marginal effect of duration of lactation on weaning-to-estrus interval (EW = 120 +/- 3; CW = 112 +/- 3 h; P < 0.06) and duration of estrus (EW = 52.4 +/- 2.3; CW = 46.3 +/- 2.2 h; P < 0.08). Overall, embryonic survival, not ovulation rate, seems to be the limiting factor for potential litter size in the second parity. Although fertility in both EW and CW sows studied was compromised, endocrine and metabolic data indicate that the mechanisms affecting reproductive performance may differ between the two weaning systems. The LH, FSH, and estradiol data from the EW sows are characteristic of animals with limited follicular development and incomplete recovery of the hypothalamic-pituitary-ovarian axis; consequently, the integrity of the uterine environment may be adversely affected and limit embryonic survival. In CW sows, variability in metabolic state seemed to be the key factor limiting the fertility, again adversely affecting embryonic survival.