Fireblight in Kent, England in relation to weather (1955–1976)

A system for the assessment of potential for fireblight Erwinia amylovora activity (PFA), based on standard temperature and rainfall records, has previously been outlined. Here some recent modifications are described and the system is discussed more fully and tested for its ability to explain outbreaks of fireblight in different hosts in Kent, south-east England for the years 1955–76. In most cases, there was a satisfactory match between PFA patterns and recorded field outbreaks and incidents and it is concluded that warnings based on the system could have lessened risk of disease in some hosts in past years. In the short term (depending on the accuracy of weather forecasts) the system can be used predictively. Its use in this way is discussed together with underlying principles of some of the criteria used and possible ways in which the precision of the system might be improved.     

Fireblight Erwinia amylovora and weather: a comparison of warning systems

Warning systems for fireblight Erwinia amylovora developed in New York, Illinois and California, USA, and in south-east England are compared. General principles which might be applicable in the different climates were sought. The consequences of applying threshold temperature values chosen for one area in a different climatic area were examined using Sacramento, California; Rochester, New York; Vlissingen, The Netherlands; Kent, England as examples. A graded system for assessing fireblight risks, derived from all the systems, is suggested. It takes into account both risks of infection and risks of high insect activity and it is best used in conjunction with Billing's incubation period assessment system.     

The occurrence, hosts and properties of lilac chlorotic leafspot virus, a newly recognised virus from Syringa vulgaris

Lilac chlorotic leafspot virus (LCLV), a hitherto undescribed virus, was isolated from three of 65 lilacs (Syringa vulgaris) with chlorotic leafspotting symptoms growing in S.E. England. The virus was transmitted readily by sap-inoculation to 21 of 52 species from eight of 20 families, but it was not seed-borne in four hosts or transmitted in the semi-persistent manner by any of four aphid species. The virus was moderately stable in vitro; sap from Chenopodium quinoa was infective after 10 min at 60 but not 65 ^oC, after 8–16 days at 20 ^oC or 25–30 wk at 2 ^oC, and after dilution to 10^-3 but not 10^-4. Up to 180 mg of purified virus per kg leaf tissue were obtained from C. quinoa by clarification of buffered leaf extracts with 8% (v/v) n-butanol, followed by one cycle of differential centrifugation and molecular permeation chromatography on controlled pore glass beads (700 Å, 120–200 mesh). LCLV has fragile flexuous filamentous particles which, when intact, mostly measured c. 12-5 times 1500–1600 nm; the helical substructure (pitch c. 3–7 nm) was clearly visible on some particles mounted in uranyl acetate. The particles sedimented as a single component (sedimentation coefficient 96 S; buoyant density 1–302 g cm^-3) and contained c. 5% nucleic acid and a single polypeptide of mol. wt 27 times 10³. Although these properties place LCLV in the closterovirus group, the virus showed no serological relationship to any of six closteroviruses (beet yellows, beet yellow stunt, carnation necrotic fleck, apple chlorotic leafspot, apple stem grooving and potato virus T) and differed from other recognised or possible members of this group in host range and/or symptoms induced in indicator species. The infrequent occurrence of LCLV in lilac in S.E. England indicates that the virus could probably be eradicated by selecting only virus-free plant material for propagation.     

Secondary leaf fall of Hevea brasiliensis: meteorological and other factors affecting infection by Colletotrichum gloeosporioides

The lower leaf surface of Hevea brasiliensis was more susceptible to infection by Colletotrichum gloeosporioides than the upper. Few lesions were produced if spore drops on susceptible leaves were allowed to dry. Lesion development after 72 h was quickest at 21 ^oC, slower at 26.5 ^oC and was stopped at 32 ^oC, probably because of bacteria in the inoculation drop. On leaflets aged 7 days from bud-burst, the effective spore dose for 50% of leaflets infected (ED₅₀) after 16 h incubation, was 260 spores and after 46 h, 120 spores/infection droplet; the minimum ED₅₀ for the upper leaf surface was about 4 spores/mm². Leaflets 15 days old, which are normally resistant, were rendered susceptible by abrading the surface with carborundum powder. Spores caught in a Hirst spore trap reached a daily maximum at 23 h, at rates of up to 440 spores/m³ air/h, but fell to low concentrations as the humidity dropped during the daytime, and also during rain. There was some correlation between disease severity and duration of 97–100% relative humidity, and moderate to severe defoliation of clone PB 86 occurred when this reached 13.5 h/day. Rainfall increases infection by prolonging the period of atmospheric saturation and leaf wetness.     

Saturable K+ pathway across the outer border of frog skin (Rana temporaria): Kinetics and inhibition by Cs+ and other cations

Summary The reaction of abdominal skins of the frog speciesRana temporaria on mucosal K⁺-containing solutions was studied in an Ussing-type chamber by recording transepithelial potential difference (PD), short-circuit current (SCC) and conductance (G). With Na-Ringer's as serosal medium, a linear correlation between PD and the logarithm of the mucosal K⁺-concentration ([K] _o ) was obtained. The K⁺-dependent SCC saturated with increasing [K] _o , and could quickly and reversibly be depressed by addition of Rb⁺, Cs⁺, and H⁺, Li⁺, Na⁺, and NH ₄ ⁺ did not influence K⁺ current. A large scatter was obtained for kinetic parameters like the slope of the PD-log [K] _o -line (18–36.5 mV/decade), the apparent Michaelis constant (13–200mm), and the maximal current of the saturable SCC (6–50 A·cm^–2), as well as for the degree of inhibition by Cs⁺ ions. This seemed to be caused by a time-dependent change during long time exposure to high [K] _o (more than 30 sec), thereby inducing a selectivity loss of K⁺-transporting structures, together with an increase in SCC andG and a decrease in PD. Short time exposure to K⁺-containing solutions showed a competitive inhibition of K⁺ current by Cs⁺ ions, and a Michaelis constant of 6.6mm for the inhibitory action of Cs⁺. Proton titration resulted in a decrease of K⁺ current at pH<3. An acidic membrane component (apparent dissociation constant 2.5×10^–3 m) is virtually controlling K⁺ transfer. Reducing the transepithelial K⁺-concentration gradient by raising the serosal potassium concentration was accompanied by the disappearance of SCC and PD.     

Factors affecting bacterial black spot of mangoes caused by Xanthomonas campestris pv. mangiferaeindicae

Bacterial black spot of mango caused by Xanthomonas campestris by. mangiferaeindicae was found to be essentially a wound pathogen of leaves under glasshouse conditions, with maximum infection occurring at a temperature regime of 22/26 ^oC (night/day). There were significant differences in leaf susceptibility among cultivars, cv. Sensation being less, and cv. Haden more susceptible than cvs Zill and Kent, which agrees with field observations of fruit infection. The organism is a phylloplane resident year round in the field and inoculum levels in the tree canopy affect ultimate fruit infection. The major weather factor affecting fruit infection was rainfall which showed a significant correlation (r = 0–77) with levels of infection after allowing for an approximate 2 wk latent period. Other significant correlations were with a wind/rain index (r = 0–73) and a storm index (r = 0–66). The correlation of disease with the duration of free water was non-significant (r = 0–22).     

Thermal inactivation of cherry leaf roll virus in tissue cultures of Nicotiana rustica raised from seeds and meristem-tips

Nicotiana rustica tissue cultures derived from seeds or embryos infected with cherry leaf roll virus (CLRV), remained infected after culture at 22 ^oC. No infectivity was found in cultures held at 32 ^oC for 5 days but it was readily detected after such cultures were transferred to 25 ^oC for 8 days. Virus was permanently eradicated from most plants after 20 days incubation at 32 ^oC and from all plants after 7 days incubation at 40 ^oC. Partially purified preparations of CLRV lost infectivity after 9–12 days at 22^oC, 5 days at 32^oC and 3 days at 40^oC.     

Effect of high soil temperatures on nodulation of cowpea, Vigna unguiculata

Cowpeas, inoculated with one of five effective strains of Rhizobium isolated from African soils, were grown at root temperatures of 30 ^oC continuously or at 36, 38, 40, 42 and 44 ^oC for 5 h/day and returned to glasshouse ambient for the intermediate period. Growth was best at 30 and 36 ^oC; above 40 ^oC growth was poor and no nodules formed. At 40 ^oC two strains failed to nodulate. Symbiotic performance was not dependent only on nodule production as nodule efficiency varied inversely with temperature. The number of nodules formed by strain R5000 after exposure of inoculated seed or seedlings to 40,42 or 44 ^oC for 5 h/day on each of 3 or 6 days depended on the age of plant and the duration of exposure to stress. When exposed to 42 or 44 ^oC during the first 3 days after sowing nodulation was reduced from 18 to 1–3 nodules/plant even after a further 40 days growth at ambient (30 day, 20 ^oC night). Nodulation was unaffected when 10–15-day-old seedlings were exposed to the same conditions. Numbers of strain R5000 on seed declined rapidly following three daily exposures of 5 h at 39 and 42 ^oC; at 45 ^oC less than three bacteria survived on each seed. Other rhizobia of the cowpea group varied greatly in their toleration of high temperatures, some survived well at 45 ^oC whereas others behaved like R5000.     

LRRK2 mutation in familial Parkinson’s disease in a Taiwanese population: clinical, PET, and functional studies

Pathogenic mutations in leucine-rich repeat kinase 2 (LRRK2) cause autosomal-dominant familial Parkinson’s disease (PD). We performed clinical, imaging, and molecular functional studies in one family with the R1441H and six families with the G2385R variants of Lrrk2. To determine the contribution of these variants to familial PD in Taiwanese, we screened 32 Taiwanese or ethnic Chinese patients with familial PD for four pathogenic substitutions (R1441H, I2012T, I2020T, and G2019S) and one susceptibility polymorphism (G2385R). The frequencies of R1441H and G2385R were 3.7% and 22.2%, respectively. G2019S, I2012T, and I2020T were not detected. The clinical phenotypes and [¹⁸F]-dopa PET findings for subjects with R1441H or G2385R resembled those of patients with idiopathic PD; however, their lymphoblastoid cell lines showed increased apoptosis following exposure to a proteosome inhibitor. Thus, LRRK2 mutations are rare in Taiwanese with familial PD. Further study is needed to identify causative genes or unique biomarkers for familial PD.     

Relationship between Late Soybean Diseases Complex and Rain in Determining Grain Yield Responses to Fungicide Applications

Wide distribution of soybean monoculture associated with no tillage has contributed to enhance damages caused by late diseases complex (LDC) in Argentina. LDC is a complex of diseases where Septoria glycines and Cercospora kikuchii are regarded as the major problem. Even though the use of foliar fungicides has increased, there is no rational and economic guide for their use. This is the main reason why the response to foliar fungicide applications is unpredictable. One of the main factors that contribute to the development of LDC is rainfall. The objective of this study was to evaluate the impact of rainfall during several growing seasons and different soybean growth stages on LDC severity and yield. We carried out 18 field experiments during three growing seasons (2004–2006) at several locations in the Argentine Pampas Region, to examine the relationship between rain and yield response to single fungicide applications (quinone outside inhibitors and demethylation inhibitors) at growing stages R3 and R5. The strongest associations (R² = 0.81–0.84; P < 0.001) were observed between accumulated rainfall from R3 to R5 and yield response to fungicides applied in R3 or R5. Our results suggest that a minimum of 65–90 mm rainfall during R3–R5 is required to justify fungicide application, with high probability that the use of fungicide will increase soybean yield as a consequence of disease control. These findings could lead to a simple model, useful as decision support system for use in planning and scheduling spray applications for LDC management in soybean crops.     

Principal Component Analysis of Multimodal Neuromelanin MRI and Dopamine Transporter PET Data Provides a Specific Metric for the Nigral Dopaminergic Neuronal Density

The loss of dopaminergic (DA) neurons in the substantia nigra (SN) is a major pathophysiological feature of patients with Parkinson''s disease (PD). As nigral DA neurons contain both neuromelanin (NM) and dopamine transporter (DAT), decreased intensities in both NM-sensitive MRI and DAT PET reflect decreased DA neuronal density. This study demonstrates that a more specific metric for the nigral DA neuronal density can be derived with multimodal MRI and PET. Participants were 11 clinically diagnosed PD patients and 10 age and gender matched healthy controls (HCs). Two quantities, the NM-related index (R_NM) and the binding potential of the radiotracer [¹⁸F]FE-PE2I to DAT (BP_ND) in SN, were measured for each subject using MRI and PET, respectively. Principal component analysis (PCA) was applied to the multimodal data set to estimate principal components. One of the components, PC_P, corresponds to a basis vector oriented in a direction where both BP_ND and R_NM increase. The ability of BP_ND, R_NM and PC_P to discriminate between HC and PD groups was compared. Correlation analyses between the motor score of the unified Parkinson''s disease rating scale and each metric were also performed. PC_P, BP_ND and R_NM for PD patients were significantly lower than those for HCs (F = 16.26, P<0.001; F = 6.05, P = 0.008; F = 7.31, P = 0.034, respectively). The differential diagnostic performance between the HC and PD groups as assessed by the area under the receiver-operating characteristic curve was best for PC_P (0.94, 95% CI: 0.66–1.00). A significant negative correlation was found between the motor severity score and PC_p (R = -0.70, P<0.001) and R_NM (R = -0.52, P = 0.015), but not for BP_ND (R = -0.36, P = 0.110). PCA of multimodal NM-sensitive MRI and DAT PET data provides a metric for nigral DA neuronal density that will help illuminate the pathophysiology of PD in SN. Further studies are required to explore whether PCA is useful for other parkinsonian syndromes.     

A comparative study of different temperature accumulation methods for predicting the start of the Quercus pollen season in Cordoba (South West Spain)

The aim of the present paper is to study the influence of air temperature on the start of Quercus pollination in Córdoba (Andalusia, Spain). Sixteen years of pollen counts were used. The start date of the pollen season in this period varied between 26^th February and 7^th April. Chilling requirements and heat accumulation were taken into account although no significant correlation between chilling hours and the start date was observed. Five different predictive methods based on heat accumulation were compared in this paper: 1) Number of days over a threshold; 2) Heat Units (accumulated daily mean temperature after deducting a base temperature); 3) Growing Degrees Days (Snyder 1988), as a measure of physiological growing time; 4) Accumulated maximum temperatures; and 5) Mean maximum temperature. Results indicated that the optimum base temperature for heat accumulation was 11 C^o. This threshold was used in the first three methods mentioned above. Good statistical results were obtained with the five methods, yielding high levels of explanation (p～99%). Nevertheless, the most accurate method appeared to be the Growing Degree Days (GDD^o) method, which indicated that a mean of 127.3 GDD^o must be accumulated from the end of the chilling period up to the beginning of the Quercus pollen season in Córdoba (South West Spain). Results were tested for predicting start dates in 1999 and 2000. The predicted dates were only one day after the actual dates.     

Transport Systems of Ventricaria ventricosa: I/V Analysis of Both Membranes in Series as a Function of [K+] o

The current-voltage (I/V) profiles of Ventricaria (formerly Valonia) membranes were measured at a range of external potassium concentrations, [K⁺] _o , from 0.1 to 100 mm. The conductance-voltage (G/V) characteristics were computed to facilitate better resolution of the profile change with time after exposure to different [K⁺] _o . The resistance-voltage (R/V) characteristics were computed to attempt resolution of plasmalemma and tonoplast. Four basic electrophysiological stages emerged: (1) Uniform low resistance between −60 and +60 mV after the cell impalement. (2) High resistance between +50 and +150 for [K⁺] _o from 0.1 to 1.0 mm and hypotonic media. (3) High resistance between −150 and −20 mV for [K⁺] _o of 10 mm (close to natural seawater) and hypertonic media. (4) High resistance between −150 and +170 mV at [K⁺] _o of 100 mm. The changes between these states were slow, requiring minutes to hours and sometimes exhibiting spontaneous oscillations of the membrane p.d. (potential difference). Our analysis of the I/V data supports a previous hypothesis, that Ventricaria tonoplast is the more resistive membrane containing a pump, which transports K⁺ into the vacuole to regulate turgor. We associate state (1) with the plasmalemma conductance being dominant and the K⁺ pump at the tonoplast short-circuited probably by a K⁺ channel, state (2) with the K⁺ pump ``off' or short-circuited at p.d.s more negative than +50 mV, state (3) with the K<sup>+</sup> pump ``on,' and state (4) with the pump dominant, but affected by high K⁺. A model for the Ventricaria membrane system is proposed. Received: 5 November 1998/Revised: 11 May 1999     

3D-QSAR,molecular docking and molecular dynamics studies of a series of RORγt inhibitors

The discovery of clinically relevant inhibitors of retinoic acid receptor-related orphan receptor-gamma-t (RORγt) for autoimmune diseases therapy has proven to be a challenging task. In the present work, to find out the structural features required for the inhibitory activity, we show for the first time a three-dimensional quantitative structure–activity relationship (3D-QSAR), molecular docking and molecular dynamics (MD) simulations for a series of novel thiazole/thiophene ketone amides with inhibitory activity at the RORγt receptor. The optimum CoMFA and CoMSIA models, derived from ligand-based superimposition I, exhibit leave-one-out cross-validated correlation coefficient (R²_cv) of .859 and .805, respectively. Furthermore, the external predictive abilities of the models were evaluated by a test set, producing the predicted correlation coefficient (R²_pred) of .7317 and .7097, respectively. In addition, molecular docking analysis was applied to explore the binding modes between the inhibitors and the receptor. MD simulation and MM/PBSA method were also employed to study the stability and rationality of the derived conformations, and the binding free energies in detail. The QSAR models and the results of molecular docking, MD simulation, binding free energies corroborate well with each other and further provide insights regarding the development of novel RORγt inhibitors with better activity.     

Pepper veinal mottle virus-a new member of the potato virus Y group from peppers (Capsicum annuum L. and C. frutescens L.) in Ghana

Pepper veinal mottle virus (PVMV), a previously undescribed virus widespread in Capsicum annuum and C. frutescens in the Eastern Region of Ghana, is acquired and inoculated in 2 min feeding periods by aphids (Myzus persicae and Aphis gossypii); it is transmissible by inoculation of sap to eleven of fifteen Solanaceae and to five of forty-six other species within three of seventeen other families. The virus was propagated in Nicotiana clevelandii and Petunia hybrida, and assayed in Chenopodium quinoa, C. amaranticolor and C. murale. Sap from Capsicum annuum was infective after dilution to 10^-3 but not 10^-4, after 10 min at 55 but not 60^oC, and after 7 but not 8 days at 25^oC. Lyophilized sap from P. hybrida was infective after 6 years in vacuo. Yields of 10–25 mg of virus per kg of leaf tissue were consistently obtained from P. hybrida or N. clevelandii by extracting systemically infected leaves in 0.5 M borate (pH 7.8) containing 0.2% mercaptoethanol and chloroform, followed by repeated precipitation with 50 g polyethylene glycol (M.W. 6000) per l, several cycles of differential centrifugation and centrifugation in sucrose density-gradient columns. Virus preparations had ultraviolet absorption spectra typical of a nucleoprotein containing c. 6% nuclei acid (A 260/280 = 1.25; A 260/246 = 1.27) and contained numerous unaggregated and unbroken filamentous particles c. 770 times 12 nm which sedimented as a single component with a sedimentation coefficient (s^o_20,w) of 155 S. PVMV contained RNA (moles %: G = 24, A = 23, C = 27, U = 26), and a single protein species with a molecular weight of 32000–33000 daltons. PVMV was not serologically related to potato virus Y (three strains), or to twelve other morphologically similar viruses, and seems to be a distinct member of the potato virus Y group. The cryptogram of PVMV is R/(I):*/(6):E/E:S/Ap.     

The infection of apples by Phytophthora syringae

Contamination with infected soil has led to high wastage of apples in storage due to rotting by Phytophthora syringae. At 3-3 ^oC lesions formed 3–4 wk after inoculation with zoospores; the percentage infection fell if the suspensions dried after 48 h at this temperature and after 22 h at 15 ^oC. Infected soil rotted fruit only if kept moist; at 3-3 ^oC a 3-day period of wetness resulted in 37-5% rotting after 8 wk. Fruit dipped in soil slurry remained wet in some parts of a 4361(12 bushel) bin for at least 3 wk. There was a 10-fold increase in rotting by contact between sound and rotting fruit after 11 wk at 3-3 ^oC. Captan gave effective protection against rotting derived from zoospores or infected soil; it had no eradicant action.     

Hatching from cysts and egg sacs of Heterodera cruciferae and effects of temperature on hatching and development on oilseed rape

Juveniles hatched readily from field cysts and very readily from eggs in egg sacs of Heterodera cruciferae, when exposed to oilseed rape root diffusate. They hatched very poorly, however, from white or brown females from which the above egg sacs had been removed. Some hatching occurred at 8 ^oC but much more occurred at 12 , 16, 20 and 24 ^oC, with most at 16 ^oC. Development of juveniles in roots of oilseed rape occurred throughout the range 8–24 ^oC, and proceeded faster the higher the temperature. The basal development temperature was taken as 5 ^oC and the number of day degrees above this temperature required to reach each stage of development was calculated. From invasion of roots to the hatching of F₁ juveniles required an average of 680 day degrees, but only 210 day degrees were required for the first appearance of egg sacs on adult females. On this basis, two consecutive generations of H, cruciferae would be possible on autumn-sown oilseed rape in southern England, but the second would mature fully only after the crop was harvested. In Scotland, two consecutive generations could also occur but the second would be much less mature by harvest: only about 850 day degrees are available compared to almost 1100 in southern England. In practice, however, overlapping generations probably occur due to flushes of hatching of juveniles (i) at sowing, (ii) when soils warm up after winter and (iii) when the first generation completes its development. The proportion of eggs found in egg sacs was never more than 37% and some field cysts contained about 220 eggs; their egg sacs may, therefore, have contained as many as 150 eggs. Any study of population dynamics or damage assessment will require a quantification of the contribution of eggs in egg sacs to population density. Oilseed rape is direct drilled and may, therefore, be more sensitive to a given population density of the nematode than host crops which are transplanted.     

Age and growth of Atlantic bluefin tuna, Thunnus thynnus (Osteichthyes: Thunnidae), in the Mediterranean Sea

The objective of the study was to describe the biometry of Mediterranean bluefin tuna, Thunnus thynnus, the biology of which is not yet well understood. A total of 504 specimens was collected from 1998 to 2005 in the central part of the Mediterranean basin. They were sexed and measured; fork lengths (FL) ranged from 51.0 to 255.0 cm while body weights (W) ranged from 2.6 to 247.0 kg. The first spiniform ray (spine) of the first dorsal fin was removed and cross‐sectioned near the condyle base in order to count annuli for age estimation. The regression coefficient (b) of the female FL–W relationship was significantly higher than that of the male, and both sexes displayed a negatively allometric growth (b < 3); male regression equation: ln W = ?2.942 + 2.730 ln FL; female regression equation: ln W = ?3.660 + 2.878 ln FL. Based on counts of the translucent zones in the sections of the first ray of the first dorsal fin, estimated ages ranged from 1 to 15 years for males and 1 to 14 years for females. The correlation between the spine ray (R) and FL fit the allometric model best; the R–FL regression equations of the two sexes did not differ significantly and the overall equation was: ln FL = 3.721 + 0.851 ln R. Due to the R–FL allometric correlation, estimates of fork lengths at previous ages, FL_i, were back‐calculated with a body proportional hypothesis. Von Bertalanffy growth equations were derived from both observed and back‐calculated FLs‐at‐age, which did not differ significantly. Moreover, no significant difference was found between the growth equations of the two sexes; the overall equation was FL_t = 373.08 [1?e^{?0.07(t + 1.76)}]. Weight‐at‐age values were derived from the von Bertalanffy predicted FLs‐at‐age by the FL–W correlation equations for males and females. The paper represents the first comprehensive study on the biometry, including age and growth, of bluefin tuna captured in the Mediterranean Sea.     

The Association Between Male Offspring Aggression and Paternal and Maternal Behavior of Peromyscus Mice

Parents influence offspring aggression through genetic and non‐genetic mechanisms, although the latter are less well understood. To examine potential non‐genetic effects of parents on offspring, we cross‐fostered the highly aggressive and biparental California mouse (Peromyscus californicus) and the less aggressive, less parental white‐footed mouse (Peromyscus leucopus). In‐fostered animals within each species were used as controls. We examined associations between the foster parents’ behavior and aggression of the fostered male offspring in resident–intruder (R–I) and neutral arena aggression tests. When both species and fostering groups were combined, R–I aggression of offspring was positively associated with paternal time spent retrieving pups. In contrast, aggression in a neutral arena was negatively associated with a composite score of maternal behavior. We discuss how our findings regarding paternal retrievals may explain previously reported effects of cross‐fostering on male aggression.