The effect of carrier substrate, dose rate and time of application on biocontrol efficacy of fungal antagonists against Armillaria root rot of strawberry plants.

In a glasshouse experiment using potted strawberry plants (cv. Cambridge Favourite) as hosts, the effect of selected fungal antagonists grown on 25 or 50 g of mushroom compost containing autoclaved mycelia of Agaricus bisporus, or wheat bran was evaluated against Armillaria mellea. Another glasshouse experiment tested the effect of application time of the antagonists in relation to inoculations with the pathogen. A significant interaction was found between the antagonists, substrates and dose rates. All the plants treated with Chaetomium olivaceum isolate Co on 50 g wheat bran survived until the end of the experiment which lasted 482 days, while none of them survived when this antagonist was added to the roots of the plants on 25 g wheat bran or 25 or 50 g mushroom compost. Dactylium dendroides isolate SP had a similar effect, although with a lower host survival rate of 33.3%. Trichoderma hamatum isolate Tham 1 and T. harzianum isolate Th23 protected 33.3% of the plants when added on 50 g and none when added on 25 g of either substrate, while 66.7% of the plants treated with T. harzianum isolate Th2 on 25 g, or T viride isolate TO on 50 g wheat bran, survived. Application of the antagonists on mushroom compost initially resulted in development of more leaves and healthier plants, but this effect was not sustained. Eventually, plants treated with the antagonists on wheat bran had significantly more leaves and higher health scores. The plants treated with isolate Th2 and inoculated with Armillaria at the same time had a survival rate of 66.7% for the duration of the experiment (475 days), while none of them survived that long when the antagonist and pathogen were applied with an interval of 85 days in either sequence. C. olivaceum isolate Co showed a protective effect only, as 66.7% of the plants survived when they were treated with the antagonist 85 days before inoculation with the pathogen, while none of them survived when the antagonist and pathogen were applied together or the infection preceded protection.

Distribution of nutrients in the root zone affects yield, quality and blossom end rot of tomato fruits

Tomato plants (Lycopersicon esculentum Mill. 'DRK') were grown hydroponically in two experiments to determine the effects of nutrient concentration and distribution in the root zone on yield, quality and blossom end rot (BER). The plants were grown in rockwool with their root systems divided into two portions. Each portion was irrigated with nutrient solutions with either the same or different electrical conductivity (EC) in the range 0 to 6 dS m(-1). In both experiments, fruit yields decreased as EC increased from moderate to high when solutions of equal concentration were applied to both portions of the root system. However, higher yields were obtained when a solution with high EC was applied to one portion of the root system and a solution of low EC to the other portion. For example, the fresh weight of mature fruits in the 6/6 treatment was only 20% that of the 3/3 treatment but the 6/0 treatment had a yield that was 40% higher. The reduction in yield in the high EC treatments was due to an increase in the number of fruits with BER and smaller fruit size. BER increased from 12% to 88% of total fruits as EC increased from 6/0 to 6/6 and fruit length decreased from 67 mm to 52 mm. Fruit quality (expressed as titratable acidity and soluble solids) increased as EC increased. In summary, high yields of high quality tomatoes with minimal incidence of BER were obtained when one portion of the root system was supplied with a solution of high EC and the other portion with a solution of moderate or zero EC.

Uneven distribution of nutrients in the root zone affects the incidence of blossom end rot and concentration of calcium and potassium in fruits of tomato

Tomato plants ( Lycopersicon esculentum Mill. var. DRK) were grown hydroponically to determine the effect of an uneven distribution of nutrients in the root zone on blossomend rot (BER) and Ca and K concentrations in the fruits. The plants were grown in rockwool with their root system divided into two portions. Each portion was irrigated with nutrient solutions with either the same or the different electrical conductivity (EC) in the range 0 to 6 dS m(-1). Solutions with high EC supplied to both sides of the root system significantly increased the incidence of BER. However, when only water or a solution of low EC was supplied to one portion, BER was reduced by 80%. Fruit yields were significantly higher ( P < 0.01) for plants that received solutions of the uneven EC treatments (6/0 or 4.5/0 EC treatment). Plants supplied with solutions of uneven EC generally had higher leaf and fruit concentrations of Ca but lower concentrations of K than those supplied with solutions of high EC. There was no difference in Ca concentration at the distal end of young fruits of the uneven EC treatment but it was reduced in the high EC treatments. The concentration of K in the mature fruits of the uneven EC treatments was lower than that of the high EC treatments and higher or similar that of the 3/3 or 2.5/2.5 EC treatments ( controls). A clear relationship was found between the incidence of BER and the exudation rate. High rate of xylem exudation was observed in the uneven EC treatments. Reduction of BER in the uneven EC treatments is most likely to be the effect of high exudation rate on Ca status in the young fruits. It was concluded that high EC of solution had positive effects on Ca concentration and incidence of BER provided that nutrient solution with low EC or water is supplied to the one portion of the root system.

Managing Armillaria root rot

Controlling Armillaria infections by physical and chemical methods alone is at present inadequate, ineffective, or impractical. Effective biological control either alone or in integration with another control strategy appears necessary. Biological control agents of Armillaria function by the antagonists inhibiting or preventing its rhizomorphic and mycelial development, by limiting it to substrate already occupied, by actively pre-empting the substrate, or by eliminating the pathogen from substrate it has already occupied. Among the most thoroughly investigated antagonists of Armillaria are Trichoderma species. Depending on the particular isolate of a Trichoderma species, control may be achieved by competition, production of antibiotics, or by mycoparasitism. The level of control is also influenced by the growth and carrier substrate of the antagonist, time of application in relation to the occurrence of the disease, and several environmental conditions. Among a range of the other antagonists are several cord-forming fungi and an isolate of Dactylium dendroides. Integrating biological methods with an appropriate method of chemical could control the disease more effectively. However it is essential to determine whether the antagonist or the fungicide should be applied first, and the time interval between.

In vitro studies on colonization resistance of the human gut microbiota to Candida albicans and the effects of tetracycline and Lactobacillus plantarum LPK

An anaerobic three-vessel continuous-flow culture system, which models the three major anatomical regions of the human colon, was used to study the persistence of Candida albicans in the presence of a faecal microbiota. During steady state conditions, overgrowth of C. albicans was prevented by commensal bacteria indigenous to the system. However antibiotics, such as tetracycline have the ability to disrupt the bacterial populations within the gut. Thus, colonization resistance can be compromised and overgrowth of undesirable microorganisms like C. albicans can then occur. In this study, growth of C. albicans was not observed in the presence of an established faecal microbiota. However, following the addition of tetracycline to the growth medium, significant growth of C. albicans occurred. A probiotic Lactobacillus plantarum LPK culture was added to the system to investigate whether this organism had any effects upon the Candida populations. Although C. albicans was not completely eradicated in the presence of this bacterium, cell counts were markedly reduced, indicating a compromised physiological function. This study shows that the normal gut flora can exert 'natural' resistance to C. albicans, however this may be diminished during antibiotic intake. The use of probiotics can help fortify natural resistance.

Comparison of the antidiabetic activity of Berberis lyceum root extract and berberine in alloxan-induced diabetic rats

Berberine has been shown to have hypoglycaemic activity in several in vitro and in vivo models, although the mechanism of action is not fully known. Berberis lyceum Royle root produces high concentrations of berberine, and in traditional medicine, the whole extract of this plant is used widely to treat diabetes. The antidiabetic activity of the ethanol root extract of Berberis lyceum was compared with pure berberine in normal and alloxan-diabetic rats using similar doses of each. The concentration of berberine in the extract was determined to be 80% dry weight with only trace amounts of other alkaloids present. The purpose of the study was to investigate the effects of berberine and a whole extract of Berberis lyceum on blood glucose and other parameters associated with diabetes, to compare the effects of the crude extract with those of pure berberine and thus validate its use as a therapeutic agent, and finally to identify any contribution of the other components of the extract to these effects. Oral administration of 50 mg/kg of Berberis extract and berberine to normal and experimental diabetic rats produced a significant (p < 0.05) reduction in blood glucose levels from days 3-7 days of treatment. Significant effects were also observed on the glucose tolerance, glycosylated haemoglobin, serum lipid profiles and body weight of experimental animals. Berberis extract and berberine demonstrated similar effects on all parameters measured, and although the extract was comparable in efficacy to berberine, it did not produce any effects additional to those shown by pure berberine. The results support the use of the extract in traditional medicine, and demonstrate that apart from being a highly cost-effective means of treating with berberine, the total extract does not appear to confer any additional benefits or disadvantages compared with the pure compound. Copyright (c) 2008 John Wiley & Sons, Ltd.

Increasing detection rate of user-to-root attacks using genetic algorithms

An extensive set of machine learning and pattern classification techniques trained and tested on KDD dataset failed in detecting most of the user-to-root attacks. This paper aims to provide an approach for mitigating negative aspects of the mentioned dataset, which led to low detection rates. Genetic algorithm is employed to implement rules for detecting various types of attacks. Rules are formed of the features of the dataset identified as the most important ones for each attack type. In this way we introduce high level of generality and thus achieve high detection rates, but also gain high reduction of the system training time. Thenceforth we re-check the decision of the user-to- root rules with the rules that detect other types of attacks. In this way we decrease the false-positive rate. The model was verified on KDD 99, demonstrating higher detection rates than those reported by the state- of-the-art while maintaining low false-positive rate.

Characterization of Actinomyces isolates from infected root canals of teeth: description of Actinomyces radicidentis sp. nov.

Two strains of a previously undescribed Actinomyces-like bacterium were recovered in pure culture from infected root canals of teeth. Analysis by biochemical testing and polyacrylamide gel electrophoresis of whole-cell proteins indicated that the strains closely resembled each other phenotypically but were distinct from previously described Actinomyces and Arcanobacterium species. Comparative 16S rRNA gene-sequencing studies showed the bacterium to be a hitherto unknown subline within a group of Actinomyces species which includes Actinomyces bovis, the type species of the genus. Based on phylogenetic and phenotypic evidence, we propose that the unknown bacterium isolated from human clinical specimens be classified as Actinomyces radicidentis sp. nov. The type strain of Actinomyces radicidentis is CCUG 36733.

The restoration of phytophagous beetles in species-rich chalk grasslands

This study focuses on the restoration of chalk grasslands over a 6-year period and tests the efficacy of two management practices, hay spreading and soil disturbance, in promoting this process for phytophagous beetles. Restoration success for the beetles, measured as similarity to target species-rich chalk grassland, was not found to be influenced by either management practice. In contrast, restoration success for the plants did increase in response to hay spreading management. Although the presence of suitable host plants was considered to dictate the earliest point at which phytophagous beetles could successfully colonized, few beetle species colonized as soon as their host plants became established. Morphological characteristics and feeding habits of 27 phytophagous beetle species were therefore tested to identify factors that limited their colonization and persistence. The lag time between host plant establishment and colonization was greatest for flightless beetles. Beetles with foliage-feeding larvae both colonized at slower rates than seed-, stem-, or root-feeding species and persisted within the swards for shorter periods. Although the use of hay spreading may benefit plant communities during chalk grassland restoration, it did not directly benefit phytophagous beetles. Without techniques for overcoming colonization limitation for invertebrate taxa, short-term success of restoration may be limited to the plants only.

Fine root biomass and turnover in southern taiga estimated by root inclusion nets

Fine roots play an important part in forest carbon, nutrient and water cycles. The turnover of fine roots constitutes a major carbon input to soils. Estimation of fine root turnover is difficult, labour intensive and is often compounded by artefacts created by soil disturbance. In this work, an alternative approach of using inclusion nets installed in an undisturbed soil profile was used to measure fine root production and was compared to the in-growth core method. There was no difference between fine root production estimated by the two methods in three southern taiga sites with contrasting soil conditions and tree species composition in the Central Forest State Biosphere Reserve, Russia. Expressed as annual production over standing biomass, Norway spruce fine root turnover was in the region of 0.10 to 0.24 y-1. The inclusion net technique is suitable for field based assessment of fine root production. There are several advantages over the in-growth core method, due to non-disturbance of the soil profile and its potential for very high rate of replication.

Fine root condition relates to visible crown damage in Norway spruce on acidified soils

Allochthonous Norway spruce stands in the Kysucké Beskydy Mts. (north-western Slovakia) have been exposed to substantial acid deposition in the recent past and grow in acidified soil conditions with mean pH of about 4.0 in the topsoil. We selected 90 spruce trees representing 30 triples of different crown status: healthy, stressed and declining to assess the relationship between crown and fine root status. Sequential coring and in-growth bags were applied to each triplet to investigate fine root biomass and growth in the soil depths of 0-10 and 10-20 cm. Fine root quantity (biomass and necromass), turnover (production over standing stock), morphological features (specific root length, root tip density) and chemical properties (Ca:Al molar ratio) were compared among the abovementioned health status categories. Living fine root biomass decreased with increasing stress, while the ratio of living to dead biomass increased. Annual fine root production decreased and specific root length increased in stressed trees when compared to healthy or declining trees, a situation which may be related to the position of trees in the canopy (healthy and declining – dominant, stressed – co-dominant). The Ca:Al ratio decreased with increasing crown damage, indicating a decreased ability to filter out aluminium. In conclusion, fine root status appears to be linked to visible crown damage and can be used as a tree health indicator.