Recent advances in sensing plant diseases for precision crop protection

Near-range and remote sensing techniques have demonstrated a high potential in detecting diseases and in monitoring crop stands for sub-areas with infected plants. The occurrence of plant diseases depends on specific environmental and epidemiological factors; diseases, therefore, often have a patchy distribution in the field. This review outlines recent insights in the use of non-invasive optical sensors for the detection, identification and quantification of plant diseases on different scales. Most promising sensor types are thermography, chlorophyll fluorescence and hyperspectral sensors. For the detection and monitoring of plant disease, imaging systems are preferable to non-imaging systems. Differences and key benefits of these techniques are outlined. To utilise the full potential of these highly sophisticated, innovative technologies and high dimensional, complex data for precision crop protection, a multi-disciplinary approach—including plant pathology, engineering, and informatics—is required. Besides precision crop protection, plant phenotyping for resistance breeding or fungicide screening can be optimized by these innovative technologies.     

Microbial assemblages as ecosystem engineers of sediment stability

Purpose  

Sediment erosion and transport is a governing factor in the ecological and commercial health of aquatic ecosystems from the watershed to the sea. There is now a general consensus that biogenic mediation of submersed sediments contributes significantly to the resistance of the bed to physical forcing. This important ecosystem function has mainly been linked to microalgae (“ecosystem engineers”) and their associated extracellular polymeric substances (EPS), yet little is known about the impact of bacterial assemblages and how their varying interactions with microalgae affect the overall biostabilization potential of the combined community.     

Myowater dynamics and protein secondary structural changes as affected by heating rate in three pork qualities: a combined FT-IR microspectroscopic and 1H NMR relaxometry study

The objective of this study was to investigate the influence of heating rate on myowater dynamics and protein secondary structures in three pork qualities by proton NMR T2 relaxation and Fourier transform infrared (FT-IR) microspectroscopy measurements. Two oven temperatures at 100 degrees C and 200 degrees C corresponding to slow and fast heating rates were applied on three pork qualities (DFD, PSE, and normal) to an internal center temperature of 65 degrees C. The fast heating induced a higher cooking loss, particularly for PSE meat. The water proton T21 distribution representing water entrapped within the myofibrillar network was influenced by heating rate and meat quality. Fast heating broadened the T21 distribution and decreased the relaxation times of the T21 peak position for three meat qualities. The changes in T21 relaxation times in meat can be interpreted in terms of chemical and diffusive exchange. FT-IR showed that fast heating caused a higher gain of random structures and aggregated beta-sheets at the expense of native alpha-helixes, and these changes dominate the fast-heating-induced broadening of T21 distribution and reduction in T21 times. Furthermore, of the three meat qualities, PSE meat had the broadest T21 distribution and the lowest T21 times for both heating rates, reflecting that the protein aggregation of PSE caused by heating is more extensive than those of DFD and normal, which is consistent with the IR data. The present study demonstrated that the changes in T2 relaxation times of water protons affected by heating rate and raw meat quality are well related to the protein secondary structural changes as probed by FT-IR microspectroscopy.     

Clinical observations surrounding an increased incidence of postanesthetic myopathy in halothane-anesthetized horses

BACKGROUND: During an 8-year period of clinic improvements, an increased incidence of postanesthetic myopathy (PAM) was observed in horses undergoing anesthesia. A request was made for an independent anesthesiologist to examine possible reasons for this increase. Routine methods used for anesthesia were then compared with new methods introduced by the anesthesiologist. OBSERVATIONS: Investigative observations were conducted from October 1999 to April 2000. Following premedication with xylazine or detomidine, anesthesia was induced with diazepam or guiaifenesin followed by ketamine. Maintenance of anesthesia was with halothane/O(2) with mechanical ventilation. Information was gathered from observing routine anesthetics. Seventeen horses were designated group A (October-December 1999) for which hypotension was defined as mean arterial pressure (MAP) <60 mmHg and managed using low-volume crystalloid fluid therapy, etilefrine, or dopamine. In the next 18 horses (group B), hypotension was redefined as MAP <70 mmHg, and was managed using high-volume fluid therapy and dobutamine (January-April 2000). No other changes were made. In both groups, creatine kinase (CK) and aspartate transaminase (AST) concentrations were measured before induction, 1 and 25 hours after standing. Occurrence of PAM was defined as CK and/or AST concentrations above 1000 IU L(-1) and analyzed with Fisher's exact test between groups. Muscle enzymes increased in five horses in group A (two with clinical signs) and in one horse in group B (difference between groups: p = 0.088). CONCLUSIONS: Maintaining MAP >70 mmHg with high-volume fluid therapy and dobutamine may help to reduce the severity of myopathy.     

A clinical study of the effects of rocuronium in isoflurane-anaesthetized cats

OBJECTIVE: To evaluate the neuromuscular blocking and chronotropic effects of rocuronium bromide in cats anaesthetized for surgery. STUDY DESIGN: Prospective clinical trial. ANIMALS: Twenty-two healthy cats of mixed breed presented for ovariectomy (n = 13) or castration (n = 9). Mean body mass (+/-SD) was 3.6 +/- 0.65 kg and mean age was 10.25 +/- 2.63 months. METHODS: Anaesthesia was induced with intravenous (IV) midazolam (0.3 mg kg(-1)), ketamine (3 mg kg(-1)) and butorphanol (0.4 mg kg(-1)). Tracheal intubation was performed and anaesthesia was maintained with isoflurane delivered in 100% oxygen. Neuromuscular function was monitored using acceleromyography applied at the ulnar nerve. This was stimulated by using the train-of-four (TOF) stimulus pattern (2 Hz) delivered every 15 seconds. The first train was made to establish baseline values for the first twitch (T1) and the TOF-ratio (T4:T1). Rocuronium (0.6 mg kg(-1) IV) was given and the following periods were recorded beginning at the end of injection: (1) lag time (LT) - to the first signs of T1 depression; (2) onset time (OT) - to the total ablation of T1; (3) duration of action (T1(25)) - to 25% recovery of the baseline value for T1; (4) T1(50)- to 50% baseline T1 restoration; (5) to TOF-ratios of 0.7 and 0.9. The time taken for T1 to recover from 75% to 25% depression (T1(25-75)) was also recorded. Heart rate (HR) was taken every minute for 15 minutes, beginning 5 minutes before rocuronium was injected. RESULTS: Rocuronium (0.6 mg kg(-1)) had a mean LT of 15.0 +/- 0 seconds, OT of 46 +/- 11 seconds and T1(25) of 13.2 +/- 2.7 minutes. The mean time for TOF 0.7 and 0.9 was 17.3 +/- 5.4 and 20.7 +/- 5.4 minutes respectively. The mean T1(25-75) was 4.8 +/- 2.4 minutes. No significant changes in HR were observed at any of the time intervals recorded. CONCLUSION: Rocuronium is an effective nondepolarizing muscle relaxant in the cat under the clinical conditions of this study. It has a rapid onset, a short duration of action and did not cause significant changes in HR.     

Stability of creatine monohydrate and guanidinoacetic acid during manufacture (retorting and extrusion) and storage of dog foods

The stability of creatine monohydrate (CrMH), crystallised guanidinoacetic acid (GAA‐C) and granulated GAA (GAA‐G) in a moist retorted and a dry extruded dog food formulation during production and storage was investigated. Commercial food mixtures were supplemented with CrMH, GAA‐C or GAA‐G. Uniformity after mixing and retorting or extrusion was determined based on replicate samples (moist n = 8, dry n = 10). Storage stability was evaluated at 25°C/60% relative humidity for 15 months and 40°C/75% for 6 months. Foods with CrMH were analysed for creatine (Cr) and creatinine (Crn), whereas GAA‐C and GAA‐G foods were analysed for GAA concentrations. Coefficients of variation (CV) for uniformity of the additives after mixing of moist and dry pet food formulations were below 15%, and the CV was lower in processed mixtures. Recoveries after retorting and extrusion were higher for GAA‐G (79 and 99%) and GAA‐C (89 and 86%) compared to CrMH (36 and 85%) foods. In moist CrMH food, Cr concentrations re‐increased by 54% whilst Crn concentrations decreased by 39% after storage at 25°C for 15 months. With total molar Cr + Crn remaining stable throughout storage, Crn and Cr appeared to effectively interconvert. Storage of the extruded CrMH food at 25°C for 15 months resulted in a 63% decrease in Cr and a 39% increase in Crn concentration. The decrease in Cr concentration was larger at 6 months storage at 40°C compared to 15 months storage at 25°C. Both GAA‐C and GAA‐G moist and dry foods were stable during storage (<10% decrease). This study showed that GAA is highly stable during production and storage of moist and dry canine foods whilst CrMH is relatively unstable, particularly during storage. The latter makes it difficult to establish a guaranteed Cr content in finished moist retorted and dry extruded foods with CrMH.     

Semen parameters and testicular dimensions in small breed dogs below ten‐kilogram bodyweight

Because of few available data on semen parameters in small breed dogs, the study aimed to analyse semen and measure testes of dogs ≤10.0 kg bodyweight. Semen was collected from 41 fertile stud dogs, which were divided based on bodyweight: group 1 ≤ 5.0 kg and group 2 between 5.1 and 10.0 kg. Median values for ejaculate volume (group 1: 1.2 ml; group 2: 2.2 ml), total sperm output (group 1: 110.7 × 10⁶; group 2: 215.1 × 10⁶) and testicular volume (group 1: left testicle 2.8 ml, right testicle 2.7 ml; group 2: left testicle 5.5 ml, right testicle 5.0 ml) were lower in group 1 compared to dogs of group 2 (p = .001; p = .001; both testes: p < .001). There was no difference in sperm concentration (p = .985). Based on these results, introduction of an additional weight group to the commonly used reference values is recommended, since values for ejaculate volume, total sperm output and testicular dimensions for dogs ≤5.0 kg bodyweight differed significantly from values of dogs with a bodyweight from 5.1 to 10.0 kg.     

A sterile hydroponic system for characterising root exudates from specific root types and whole-root systems of large crop plants

Background

Plant roots release a variety of organic compounds into the soil which alter the physical, chemical and biological properties of the rhizosphere. Root exudates are technically challenging to measure in soil because roots are difficult to access and exudates can be bound by minerals or consumed by microorganisms. Exudates are easier to measure with hydroponically-grown plants but, even here, simple compounds such as sugars and organic acids can be rapidly assimilated by microorganisms. Sterile hydroponic systems avoid this shortcoming but it is very difficult to maintain sterility for long periods especially for larger crop species. As a consequence, studies often use small model species such as Arabidopsis to measure exudates or use seedlings of crop plants which only have immature roots systems.

Results

We developed a simple hydroponic system for cultivating large crop plants in sterile conditions for more than 30 days. Using this system wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) plants were grown in sterile conditions for 30 days by which time they had reached the six-leaf stage and developed mature root systems with seminal, nodal and lateral roots. To demonstrate the utility of this system we characterized the aluminium-activated exudation of malate from the major types of wheat roots for the first time. We found that all root types measured released malate but the amounts were two-fold greater from the seminal and nodal axile roots compared with the lateral roots. Additionally, we showed that this sterile growth system could be used to collect exudates from intact whole root systems of barley.

Conclusions

We developed a simple hydroponic system that enables cereal plants to be grown in sterile conditions for longer periods than previously recorded. Using this system we measured, for the first time, the aluminium-activated efflux of malate from the major types of wheat roots. We showed the system can also be used for collecting exudates from intact root systems of 30-day-old barley plants. This hydroponic system can be modified for various purposes. Importantly it enables the study of exudates from crop species with mature root systems.

     

Long-term Lysimeter Experiments - Findings from Brandis Lysimeter Station 2nd Communication

The goal of these studies was to evaluate lysimeter experiments performed over a number of years on the nitrogen cycle of different soil types to estimate the potential hazard of various types of farming usage resulting from N-leaching losses into the groundwater. The studies were carried out in monolithic lysimeters measuring 1m2 with a depth of 3m located in Brandis (near Leipzig, Saxony, Germany). The soils were four pedohydrotopes (Top a-d) characterised by increasing depth, usable field capacity (nFK) and sorption capacity. The average values calculated for the experiments lasting 21 years were as follows for the extreme pedohydrotopes a and d respectively: annual nitrogen losses - 85 and 185kg/ha; annual nitrogen leaching -51 and 5kg/ha; and leachate nitrate levels - 100 and 39mg/l. Viewed on a year-by-year basis, effects due to weathering and soil type outweighed the usage-related leaching risk. Organic farming usually reduces N leaching and the leachate N level below the recommended limits. However, ploughing in clover (usually carried out in autumn to improve the supply of nutrients in biologically dynamic organic agriculture) and also spreading stable manure combined with winter black fallow raised the level of nitrate in leachate above the maxima. Hence N fertilisation as prescribed by the computer program BEFU within environmentally sustainable land use does not appear to be sufficient to significantly reduce N leaching.