Microbial community development in the rhizosphere of apple trees at a replant disease site

Apple replant disease (ARD) is a complex syndrome that affects young trees in replanted orchard sites causing necrotic lesions on feeder roots, stunted tree growth and reduced cumulative yields. Use of ARD-tolerant rootstocks is an emerging control strategy. We studied the bacterial, fungal, and oomycetes populations in the rhizosphere of five rootstock cultivars (M.7, M.26, G.16, G.30 and CG.6210) planted into the old tree row or grass lanes of a previous orchard in Ithaca, NY, to better understand the role of rhizosphere microbial communities in the prevalence and control of ARD. The possible involvement of antagonistic Pseudomonas species, Pythium spp., Phytophthora spp. and rhizosphere cyanide concentrations in ARD were also examined. The rootstocks M.7, M.26 and G.16 were susceptible to ARD, while G.30 and CG.6210 were more tolerant. Tree growth on the rootstocks M.7, M.26 and G.16 was reduced by 10% when planted in the old tree rows, but this did not significantly reduce yields in the first fruiting year. The susceptible rootstocks, M.7 and M.26, supported higher densities of culturable rhizosphere fungi and bacteria than G.16, G.30 and CG.6210. Over 2 years, microbial densities were highest in July, lower in May and lowest in September. The composition of bacterial and fungal communities in the rhizosphere was highly variable and changed over seasons and years, as assessed by terminal restriction fragment length polymorphism (T-RFLP) analyses. Initial differences in fungal rhizosphere communities between the two planting positions converged 2 years after the trees were replanted. In contrast, the bacterial rhizosphere community composition still differed significantly between the two planting positions 3 years after the orchard was replanted. The bacterial and fungal rhizosphere community compositions of susceptible rootstocks, M.7 and M.26, differed from those of the tolerant rootstocks, G.30 and CG.6210; G.16, differed from all the other rootstocks. The observed effects of rootstocks, planting positions and time on microbial community composition were small relative to the high variability observed overall. Pythium spp. and Phytophthora spp. infestations were high and similar for all rootstocks and planting positions. Neither potentially antagonistic Pseudomonas nor rhizosphere cyanide concentrations appeared to be involved in the ARD-complex at the studied site. Avoiding replanting into the old tree rows coupled with use of tolerant rootstocks appear to be the best strategies for reducing ARD in replanted orchards. Changes in rhizosphere microbial communities are among the many factors that contribute to improved tree growth when these management strategies are used.     

Ertragssimulation mit “Ceres Wheat” an Grundwasserböden gemäßigter Klimazonen. Teil 1: Anwendungsgrenzen des Originalmodelles und Modelländerungen

Calibration of the simulation model “Ceres Wheat” under conditions of soils with shallow watertable and temperate climate. Part 1: Limitations in the applicability of the original model and necessary modifications To apply the yield simulation model “Ceres Wheat” under the specific climate conditions of Schleswig Holstein, the following modifications were necessary:

• Wheat development is strongly influenced by climatic conditions. Therefore the model has been adjusted to the temperate climate of Schleswig Holstein.
• The soil water balance routine of the model was originally designed for soils without oxygen deficiencies due to water logging. Routines for shallow water tables and artificial drainage were formulated.
• Due to modifications of the soil water balance routine, the associated nitrogen routine, especially the leaching of nitrate, has been changed.
• The simulation of yield depressions due to excessive water required the introduction of a trafficability delay function and an additional reduction factor for crop development.

All routines concerning the water and nitrogen balances and the quality of simulations have been tested under conditions of coastal marsh soils in Schleswig Holstein.     

Lectin‐Binding Pattern in Ovarian Structures of Rats with Experimental Polycystic Ovaries

Numerous experimental models in different species have been developed for the study of polycystic ovarian syndrome. In this study, we used a model of induction of polycystic ovaries (PO) in rats by exposure to constant light to study the distribution and variations of glycosylated residues present in the different ovarian structures. Seven biotinylated lectins were used (Con‐A, WGA, DBA, SBA, PNA, RCA and UEA‐I) on tissue sections, and detection was performed using the streptavidin/peroxidase method. In tissue sections was observed an increase in affinity for Con‐A in the granulosa and theca interna of growing follicles and cysts in animals with PO in relation to the control group. Follicular cysts showed higher affinity for WGA and RCA‐I which growing follicles in the same group, and there was a decrease in affinity for PNA in the cysts in relation to the growth of follicles in both groups. Atretic follicles in both groups showed greater labelling with lectins PNA, SBA and RCA‐I in relation to healthy follicles. It could also be noted that the zona pellucida of cystic follicles lost the affinity for the lectin Con‐A. There was no staining on follicles in any category with the lectins DBA and UEA‐I, although it was staining in the corpus luteum (control group) and in the mesothelium and interstitial glands of both groups with DBA. These observations probably reflect changes in the glycosaminoglycans present in the different ovarian compartments or in the glycosylation of cellular components essential for proper follicular dynamics.     

Liquorice and canine Addison's disease

Abstract

Extract

Hypoadrenocorticism, or Addison's disease, is an uncommon en-docrinopathy of dogs (Feldman and Nelson 2004 Feldman, EC and Nelson, RW. 2004. “Hypoadrenocorticism (Addison's disease)”. In Canine and Feline Endocrinology and Reproduction, 3rd, 394–439. Philadelphia, , USA: WB Saunders.  [Google Scholar]). Long-term management of affected dogs in New Zealand involves treatment with oral fludrocortisone acetate (Florinef tablets; Bristol-Myers Squibb (NZ) Ltd, Auckland, NZ), which is a relatively expensive synthetic adrenocortical steroid. Table salt may be added to the food, in an attempt to reduce the amount of fludrocortisone required. Despite fludrocortisone therapy, many Addisonian dogs remain hyponatraemic and hyperkalaemic and the required dose of fludrocortisone may need to be increased during the first year of treatment. Increasing the dose of fludrocortisone is not only expensive, but may also have undesirable effects through its potent glucocorticoid action.     

Mycobacterium avium subsp. paratuberculosis infection in wildlife on three deer farms with a history of Johne's disease

Abstract

AIM: To determine the prevalence of Mycobacterium avium subsp. paratuberculosis (Map) infection in wildlife, in pastoral landscapes with a recent history of clinical Johne's disease in livestock.

METHODS: A total of 449 wild mammals and birds from three farms in the South Island of New Zealand with recent histories of clinical Johne's disease in their deer herds were trapped and examined for gross pathological changes in the gastrointestinal tract. Additionally, individual mesenteric lymph nodes from 380 mammals, and segments of gastrointestinal tract from 32 birds were excised, homogenised and cultured for viable Map bacilli. The prevalence of Map infection was then calculated for the various species. Faecal samples from those mammals which had culture-positive tissues were further cultured for the presence of Map.

RESULTS: Gross pathological changes were identified in the gastrointestinal tract of four brushtail possums, one cat, six ferrets, 12 hares, six hedgehogs, three rabbits, one stoat, and one paradise shelduck. Infection with Map in the gastrointestinal tract was confirmed in only three of these cases, one each of brushtail possums, hares and hedgehogs. In contrast, Map infection in the absence of gross pathological changes was frequently recorded in enteric tract tissues of mammals and birds. Among mammals, Map infection was recorded in 18/73 (25%) brushtail possums, 4/23 (17%) cats, 15/42 (36%) hedgehogs and 29/113 (26%) rabbits. Among birds, intestinal tract tissue Map infection was recorded in 3/17 (18%) paradise shelducks. Among 64 of the 74 mammals which had Map culture-positive tissues, 38% (n=5) of hedgehogs and 11% (n=3) of rabbits also had culture-positive faecal samples.

CONCLUSIONS: This study is the first to identify that Map infection can be prevalent in wildlife in New Zealand. There was a high prevalence of Map infection among both scavenging and grazing wild animals. Both mammals and birds are capable of harbouring viable Map organisms in their gastrointestinal tract; further, viable Map was excreted into the environment via faeces by hedgehogs and rabbits.

CLINICAL RELEVANCE: Previous studies overseas have postulated a role of wildlife as reservoirs of Map infection and possible vectors of Johne's disease to livestock. Here, brushtail possums, hedgehogs and rabbits and in particular were identified as potential wildlife hosts for Map infection in NewZealand. This suggests that several wildlife species could contribute to the persistence of Map infection within a wildlife/livestock complex, and potentially, perhaps more importantly, to the spread of infection between farms.     

Early detection of sugar beet pathogen Ramularia beticola in leaf and air samples using qPCR

A quantitative PCR method (qPCR) was developed for the detection and quantification of Ramularia beticola causing Ramularia leaf spot in sugar beet. R. beticola specific primers were designed based on the internal transcribed spacer region 2 (ITS2). The assay was applied on DNA extracted from spores trapped on tape from Burkard spore traps placed in an artificially inoculated sugar beet field trial and in two sugar beet fields with natural infections. R. beticola DNA was detected at variable amounts in the air samples 14 to 16 days prior to first visible symptoms. R. beticola DNA was detected in air samples from fields with natural infection at significant and increasing levels from development of the first symptoms, indicating that spore production within the crop plays a major role in the epidemic development of the disease. Sugar beet leaves sampled from the inoculated field trial were also tested with the qPCR assay. It was possible to detect the presence of R. beticola in the leaves pre-symptomatic at least 10 days before the occurrence of the visible symptoms of Ramularia leaf spot. This is the first report of a molecular assay, which allows screening for the presence of R. beticola in plant material and in air samples prior to the appearance of visible symptoms. An early detection has potential as a tool, which can be part of a warning system predicting the onset of the disease in the sugar beet crop and helping to optimise fungicide application.