Contradictions in host plant resistance to pests: spider mite (Tetranychus urticae Koch) behaviour undermines the potential resistance of smooth-leaved cotton (Gossypium hirsutum L.)     

Reddall AA  Sadras VO  Wilson LJ  Gregg PC 《Pest management science》2011,67(3):360-369

BACKGROUND: Two‐spotted spider mites (Tetranychus urticae Koch) oviposit near leaf veins or in leaf folds on the undersides of cotton (Gossypium hirsutum L.) leaves where the humid boundary layer offers protection from desiccation. The authors predicted that the boundary layer of glabrous cotton leaves should be shallower than that of hairy leaves, providing some resistance to mites. The dynamics of mite populations, leaf damage, leaf gas exchange and crop yield on two leaf hair isolines (smooth versus hairy) in two genetic backgrounds was assessed. RESULTS: Mite colonies developed faster on the hairy leaf isolines, but leaf damage per mite was higher in smooth leaf isolines, indicating more intense damage. A 50% reduction in photosynthesis on the hairy isolines required 1.8 times more mites than smooth leaves. The yield of cotton was reduced in + mite treatments, but the magnitude of reduction was similar for hairy and smooth isolines. CONCLUSION: Paradoxically, the relative inhospitality of glabrous leaves may have induced mites to concentrate in protected leaf sections, causing more localised and more severe damage, negating the yield benefits from fewer mites. These results highlight interactions between leaf microenvironment, pest behaviour and plant productivity that may have implications for other instances of plant resistance. Copyright © 2010 Society of Chemical Industry  相似文献   

The mineralogy and potassium supplying power of some loessial and related soils of New Zealand     

A. Surapaneni  A. S. Palmer  R. W. Tillman  J. H. Kirkman  P. E. H. Gregg 《Geoderma》2002,110(3-4):191-204

Sixteen Pallic (Aqualfs, Ustalfs, Aquepts, Ochrepts) and related soils collected from the North and South Islands of New Zealand were studied to determine if variations in nonexchangeable K supply could be explained by mineralogical composition. A strong relationship was found which indicates that mica is weathering to vermiculite. Proportions of vermiculite and kandite are generally higher in the North Island than in the South Island. Dominance of either micas or vermiculite or kandite is determined by the stage of weathering and/or the nature of parent materials. Soils that supplied more nonexchangeable K (K_nex) to ryegrass plants contained more mica in the clay fraction than soils that supplied less K_nex. The results confirmed that use of a soil test that includes a measure of K_nex (i.e. acid-extractable K) may be a vital part of identifying variations in plant available K status of the soils. It is concluded that the K supplying power of the Pallic and related soils is related directly to the amounts of mica present in clay fraction and that good K supplying soils will be transformed to K depleted soils as a result of increased weathering and leaching (pedogenic factors) and K exploitation in intensive farming systems.  相似文献   

Meiotic Response of In vitro Matured Canine Oocytes under Different Proteins and Heterologous Hormone Supplementation   总被引：2，自引：0，他引：2  

BA Rodrigues  JL Rodrigues 《Reproduction in domestic animals》2003,38(1):58-62

The impact of TCM‐199 supplemented with different proteins and heterologous hormones on the in vitro maturation (IVM) rate of bitch oocytes was evaluated by nuclear staining under fluorescence microscopy. Oocytes were recovered by slicing of ovaries from bitches presented at various stages of oestrous cycle to ovariohysterectomy. The basic culture medium was TCM‐199 supplemented with 25 mM Hepes/l, with 10% heat‐inactivated oestrous cow serum (ECS), 50 μg/ml gentamicin, 2.2 mg/ml sodium bicarbonate and 22‐μg/ml pyruvic acid, 1.0‐μg/ml oestradiol (E 8875; Sigma), 0.5‐μg/ml follicle‐stimulating hormone (FSH) (Folltropin‐V; Vetrepharm Inc., Ontario, Canada) and 0.03 IU/ml human gonadotropin (hCG) (Profasi HP; Serono, Aubonne, Switzerland). Oocytes were distributed randomly between basic culture medium (control) and the corresponding experimental treatment. Hormone treatments were: oocytes cultured in; (1) medium without FSH, (2) control medium supplemented with 20 μg/ml oestradiol, or (3) medium supplemented with 1 μg/ml human somatotropin (hST; Humatrope, Lilly, Saint Cloud, France). The second experiment consisted of oocytes cultured in medium supplemented with 0.4% (w/v) bovine serum albumin (BSA, fraction V; Gibco Grand Island, NY, USA) instead of ECS, or oocytes cultured in medium with 10% inactivated oestrous bitch serum (EBS) instead of ECS. Oocytes were cultured in 100 μl droplets (up to 25 oocytes per drop) under mineral oil at 37°C in a 100% humidified atmosphere containing 5% CO₂ in air. After 72 h of IVM, the highest rates (p < 0.05) of meiotic resumption were achieved with the 0.4% BSA supplementation. A positive influence on the metaphase II (MII) acquisition rate was observed with hST supplement. Oocytes cultured with 10% EBS supplementation did not develop to the MII stage. The results in this study show that the protein and hormone supplements to TCM‐199 culture medium tested did not promote the final steps of IVM of bitch oocytes.  相似文献   

Experimental transmission of Pasteurella multocida from raccoons to turkeys via bite wounds     

D A Gregg  L D Olson  E L McCune 《Avian diseases》1974,18(4):559-564

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Endogenous opioid suppression of release of luteinizing hormone during suckling in postpartum anestrous beef cows   总被引：1，自引：0，他引：1  

T R Myers  D A Myers  D W Gregg  G E Moss 《Domestic animal endocrinology》1989,6(3):183-190

Beef cows were used to determine if suckling influences release of LH via endogenous opioids at 28 +/- 4 d after parturition. Cows of similar weight and body condition (6.8 +/- .1, 1 = emaciated, 9 = obese) were assigned randomly to five groups (n = 6 to 7): 1) control-suckled/saline (suckled 15 min every 6 hr for 48 hr); 2) control-suckled/naloxone; 3) calf-removal/saline (calf removal for 52 hr); 4) calf-removal/naloxone; and 5) control-suckled/GnRH (Gonadotropin-Releasing Hormone). At 0 hr, saline was administered to all cows. This treatment was continued at 6 hr intervals for 24 hr. Either naloxone (0.5 mg/kg), GnRH (40 ng/kg) or saline was administered to cows in their respective groups every 6 hr during the ensuing 24-hr period in calf-removal groups, or immediately preceding each suckling episode in the control-suckled groups. Blood samples for analysis of luteinizing hormone (LH) were collected at 15-min intervals for 1 hr prior to and 3 hr after treatment at 0, 24, 36 and 48 hr. Cows were observed for estrus twice daily. All cows in the control-suckled/GnRH group released LH (P less than .05) in response to exogenous GnRH, indicating the presence of releasable quantities of the gonadotropin. Mean concentrations of LH were not effected (P greater than .05) by the control-suckled regime. However, calf-removal alone, or in combination with naloxone, increased (P less than .05) mean concentrations of LH by 48 hr.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

Relationships among concentrations of four opioid neuropeptides and luteinizing hormone-releasing hormone in neural tissues of beef cows following early weaning     

P V Malven  J R Parfet  D W Gregg  R D Allrich  G E Moss 《Journal of animal science》1986,62(3):723-733

Acute changes associated with removal of the inhibition of estrus caused by suckling were examined in beef cows. Calves were weaned during the fifth week after parturition and cows were slaughtered at 0 (n = 8), 36 (n = 8) or 72 h (n = 8) after calf removal. Tissues of preoptic area (POA), hypothalamus (HYP), pituitary stalk-median eminence (SME) and pituitary neurointermediate lobe (NIL) were obtained for analyses of luteinizing hormone-releasing hormone (LHRH) and four opioid neuropeptides. In addition, one-half of each SME was superfused in vitro for measurement of basal and potassium-induced release of LHRH. The following opioid neuropeptides were quantified: methionine-enkephalin (Met-Enk), beta-endorphin (beta-EP), dynorphin-A, 1-17 (DYN-17) and dynorphin-A, 1-8 (DYN-8). All four opioid neuropeptides were most concentrated in the pituitary NIL. Luteinizing hormone-releasing hormone was most concentrated in the SME tissue, which also contained substantial concentrations of Met-Enk and beta-EP, but very little DYN-17 or DYN-8. In addition, weaning increased the weight of NIL between 0 and 36 h (P less than .05), and the concentrations of LHRH, Met-Enk, and DYN-17 in the combined POA + HYP (P less than .05) tissue between 36 and 72 h. No differences occurred among groups in SME content of LHRH or in vitro release of LHRH from the superfused SME. Although they were not affected by weaning, within-cow correlations among parameters revealed that: 1) concentrations of DYN-17 and DYN-8 were always positively correlated (P less than .05); 2) concentrations of LHRH were positively correlated with Met-Enk (P less than .01), beta-EP (P less than .05) and DYN-17 (P less than .05) in the combined POA + HYP tissue; 3) LHRH concentrations in SME tissue were negatively related to POA + HYP concentrations of Met-Enk (P less than .01) and beta-EP (P less than .05), but not of LHRH or DYN-17 and 4) in vitro release of LHRH from the pituitary SME was correlated with concentrations of DYN-8 in various tissues including the SME (P less than .01). In summary, bovine neural tissues differ widely in concentrations of the four opioid neuropeptides with NIL tissue having the greatest concentrations. Weaning calves at 36 and 72 h before slaughter caused parallel changes in LHRH, Met-Enk and DYN-17 in preoptic and hypothalamic tissues.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   

In-vitro activity of ceftiofur against Australian isolates of the family Pasteurellaceae associated with respiratory disease in cattle and pigs     

PJ BLACKALL  JL PAHOFF  CP STEPHENS  FM DARVILL 《Australian veterinary journal》1996,74(1):71-71

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The occurrence and distribution of Salmonella enteritidis and other serovars on California egg laying premises: a comparison of two sampling methods and two culturing techniques     

Kinde H  Castellan DM  Kass PH  Ardans A  Cutler G  Breitmeyer RE  Bell DD  Ernst RA  Kerr DC  Little HE  Willoughby D  Riemann HP  Snowdon JA  Kuney DR 《Avian diseases》2004,48(3):590-594

Between the summer of 1998 and the winter of 2000, Salmonella analysis was performed on 2128 single and 532 pooled manure drag swabs obtained from 133 California commercial egg laying farms. The isolation of Salmonella from all rows and from all flocks using single or pooled swabs was 80% and 92%, respectively. Hence, there was no statistical difference between single vs. pooled swabs in terms of identifying Salmonella on a row or flock basis. A total of 14 serogroups comprising 44 serotypes were isolated from 123 of 133 farms. When the top 10 serotypes were considered, there was no significant difference in the range of serotypes isolated by the two culturing methods. The overall S. enteritidis prevalence for California flocks was 10.5% (14/133). The overall row prevalence for S. enteritidis for all the farms was 1.1% (24/2128), and the overall pool prevalence was 2.4% (13/532). Sixty percent (12/20) of the S. enteritidis isolates from the positive farms were phage type 4, and 40% (8/20) represented five other phage types (1, 6B, 7, 8, and 28).  相似文献   

Bioequivalence of a new liquid formulation of benazepril compared with the reference tablet product     

K Kelers  JL Devi  GA Anderson  P Zahra  JH Vine  T Whittem 《Australian veterinary journal》2013,91(8):312-319

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Epistaxis in racehorses: risk factors and effects on career     

JL Langford  PC Thomson  PK Knight 《Australian veterinary journal》2013,91(5):198-203

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