Protection of susceptible potato cultivars against late blight in mixtures increases with decreasing disease pressure

ABSTRACT Cultivar mixtures can reduce potato late blight severity on susceptible cultivars. While alternating rows of susceptible and resistant cultivars would be more acceptable than random mixtures for commercial use, they increase the genotype unit area, which is an unfavorable factor for mixture efficiency, and have been minimally efficient when disease pressure is high. The effects of disease pressure on the performance of alternating rows of cultivars possessing various types and levels of resistance were investigated in 2000 and 2001 near Quito, Ecuador, where natural pressure of late blight is high. The experiments included the highly susceptible cvs. Cecilia in 2000 and LBr37 in 2001, as well as C114 (moderately resistant) and PAN (highly resistant), planted as pure stands and as the three possible two-way combinations. Different disease pressures were obtained with three spraying schedules of a contact fungicide: nontreated, one spray every second week, and one spray weekly. The area under the disease progress curve (AUDPC) on the susceptible cultivar was 0 to 20% less in mixed than in pure plots when no fungicide was applied, 13 to 26% less with a biweekly application of fungicide, and 32 to 53% less with a weekly application. These values are comparable to those obtained in previous experiments in smaller plots with designs maximizing the distance between susceptible plants. No significant differences in mixture performance were observed according to the resistant cultivar included. Effects on yield were minimal, because of the impact of factors other than late blight. Disease pressure therefore appears as a major factor conditioning the efficiency of potato cultivar mixtures against late blight.     

Effect of fluoxetine on blood concentrations of serotonin, cortisol and dehydroepiandrosterone in canine aggression

Canine aggression directed towards people is the most frequent reason for referral to behaviour practices. The serotonergic system and the hypothalamic-pituitary-adrenal (HPA) axis are believed to play an important role in controlling aggression. The selective serotonin reuptake inhibitor fluoxetine is the most commonly used drug in canine aggression. The aim of the present study was to assess the effect of a 30-day-long fluoxetine treatment on the peripheral serotonergic system and the HPA axis in canine aggression. To this end, the concentrations of serum serotonin (5-HT) and plasma cortisol and dehydroepiandrosterone (DHEA) were analysed in a group of aggressive (n = 22) and nonaggressive dogs (n = 9) during pre- (day 0) and posttreatment (day 30) conditions. Treatment caused a significant decrease in 5-HT concentrations (46% in the aggressive group and 32% in the control group). There was a trend towards a rise of DHEA/cortisol ratio values after treatment both in the aggressive and the control group. The determination of blood 5-HT and the DHEA/cortisol ratio could have important clinical applications in the future for deciding which animals might benefit from a given treatment as well as for monitoring the response. Further large-scale studies with this aim should be carried out to obtain sound conclusions.     

Inheritance of the resistance toGlobodera rostochiensis pathotype Ro2 in potato

Nine advanced tetraploid potato clones withS. tuberosum ssp.tuberosum, S. tuberosum ssp.andigena, andS. vernei background were found to be highly resistant toGlobodera rostochiensis pathotype Ro2. In order to characterize the inheritance of the resistance to Ro2 and determine the genotype of these Ro2-resistant clones, a series of testcrosses to susceptibleS. tuberosum cultivars, as well as crosses between the resistant clones, were made. A total of 1081 seedlings corresponding to 18 families were grown, inoculated with 3000G. rostochiensis juveniles (J2), and evaluated by the root-ball method. To determine which genetic model best fit the data, goodness-of-fit-tests were performed. The analysis assumed tetrasomic inheritance under the hypothesis that resistance is due to one locus with complete dominance. From the analysis of the data it is concluded that there is no consistent evidence against the hypothesis that a single dominant gene is associated with the resistance to Ro2 and that the Ro2-resistant clones are simplex. In general, the number of cysts observed on the root balls was low compared with the results of other studies, the results of the different inoculations were variable, and there was an excess of resistant plants. Possible explanations for these observations are discussed.     

Scoring system for evaluating the stress to cattle of commercial loading and unloading

The loading and unloading of cattle for road transport is stressful but the stress is difficult to evaluate in terms of the welfare of the cattle. Over one year, 40 normal commercial journeys in northern Spain were analysed in terms of time limits and behavioural events in order to design an objective method for assessing the stresses imposed on the animals, and a scoring method was developed for assessing the welfare of the animals during loading and unloading. Several definitions of time intervals were assessed to calculate a time score per animal, and easily observable behavioural events were scored and combined with the time score to obtain a total loading/unloading score. More than half of the loadings and unloadings involved turns, slips and vocalisations. Mounts and bouts of fighting were infrequent and balks and falls were significantly more frequent during loading than unloading. The plasma concentrations of cortisol, glucose and lactate, the activity of creatine kinase and the pH of the meat 24 hours after the animals were slaughtered were also measured. The results indicated that loading was more stressful than unloading and that higher scores implied significantly higher levels of stress.     

Immunohistochemical expression of estrogen receptor beta in normal and tumoral canine mammary glands

To date, two isoforms of estrogen receptors (ER) have been identified, cloned, and characterized from several species, estrogen receptor-alpha (ERalpha) and estrogen receptor-beta (ERbeta). Although the presence of ERalpha has been demonstrated in normal and tumoral canine mammary tissues, the issue of ERbeta expression has not been addressed in the dog. In this study, we have analyzed the expression of ERbeta in formalin-fixed, paraffin-embedded tissue samples of nonaltered mammary gland, 30 malignant (six complex carcinoma, 12 simple carcinoma, three carcinosarcoma, and nine carcinoma or sarcoma in benign tumor), and five benign (one fibroadenoma, one complex papilloma, one complex adenoma, and two benign mixed tumors) mammary tumors of the dog by using a polyclonal ERbeta antibody and the avidin-biotin-peroxidase complex immunohistochemical technique. Our results show that high numbers of normal ductal and acinar epithelium and approximately one third of canine mammary tumors express ERbeta. This expression was higher in benign than in malignant tumors. Furthermore, expression was higher in complex and mixed histologic subtypes of malignant tumors when compared with simple subtypes.     

Detection of streptomycin resistance in Erwinia amylovora strains isolated from apple orchards in Chihuahua, Mexico

Fire blight, one of the most severe diseases of apple and pear, is caused by the bacterium Erwinia amylovora. One control method is the use of antibiotics like streptomycin; however, streptomycin is the only antibiotic registered to control fire blight. A total of 107 E. amylovora strains were isolated from apple orchards located in Cuauhtémoc and Guerrero, Chihuahua, two major apple-producing areas in Mexico, showing 40 and 24 % streptomycin-resistant strains, respectively. The identification of E. amylovora strains was performed by polymerase chain reaction (PCR) amplification of a 900-bp region located within the non-transferable pEA29 plasmid and by amplification of a specific 1,269-bp region located on the E. amylovora chromosome. The 107 isolates tested carried the pEA29 plasmid, and 36 % of the isolates from both locations showed high resistance to streptomycin at levels that ranged from 200 to ≥1,000 μg ml^?1 streptomycin. The strA-strB and aadA genes, which encode enzymes that inactivate streptomycin, and a mutation in codon 43 of the rpsL gene that confers high resistance to the antibiotic were examined to determine the mechanism of streptomycin resistance. In total, 95 % of the resistant strains showed a single base pair mutation in codon 43 of the rpsL gene, causing an amino acid substitution in ribosomal protein S12. The presence of strA-strB and aadA genes or the rpsL mutation was not identified in the other 5 % of resistant strains, suggesting the existence of a new streptomycin resistance mechanism in E. amylovora.     

Bioaccumulation of mineral elements in grapevine varieties cultivated in “La Mancha”

The capacity of a plant to take up chemical elements is measured as the ratio of the element concentration in the plant and its concentration in the soil. This ratio is called the bioaccumulation index (BAC). The choice of rootstock and variety can differentially affect nutrient uptake of grapevine (Vitis vinifera L.). Generally, only slight differences can be observed in the accumulation of N, P, and Zn. In contrast, wide variations are found in the absorption of K, Ca, Mg, and Cl. While studies on plant nutrients and major elements have been carried out in vineyards, very few references concern the trace‐element concentrations in leaves. In the study described here, five varieties (Airén, Cencibel, Garnacha, Cabernet Sauvignon, and Chardonnay) grown on a Calcisol Petric or Typic Calcixerept (typical of La Mancha) were compared in terms of leaf trace‐element concentrations. A total of three samples (20 healthy and completely developed leaves from the middle part of the shoot) were collected from three different plants of the same variety. Leaves were dried, milled, and x‐ray fluorescence analysis was performed. It was found that the variety of grapevine influences the uptake of four of the major elements: Al (low in Garnacha, [0.4 ± 0.2] g kg^–1), Ca (high in Cencibel, [32.6 ± 8.1] g kg^–1), P (low in Airén, [0.9 ± 0.4] g kg^–1) and K, which showed significant differences in almost all of the varieties (from [4.7 ± 1.8] g kg^–1 in Cencibel to [8.0 ± 10.1] g kg^–1 in Chardonnay). No statistically significant varietal differences were found for trace elements. The only exception was La, which was present at higher levels in the variety Cencibel ([7.5 ± 0.3] mg kg^–1). This finding allows to assess the geochemical fingerprinting of calcareous soils regardless of the grapevine variety studied.     

Effect of urbanization on the avifauna in a tropical metropolitan area

The rapid and unplanned expansion of urban areas is a common pattern in neotropical developing countries. Urbanization has eliminated or drastically altered large areas of natural habitats used by the rich neotropical avifauna. In our study area, in Costa Rica’s Central Valley, urbanization increased 72% in 33 years with the consequent destruction, fragmentation, and isolation of forest tracts, shade plantations, and other semi-natural habitats used by a rich avifauna. We show that over the last 16 years 32 resident species of birds have disappeared from this area. Species with specialized habitat requirements or particular life history traits (e.g., altitudinal migrants) are disproportionately represented among those birds that have disappeared from the region. Another 34 latitudinal migrants have gone undetected as nearly all habitats these species used as a stopover site during the autumn migration have disappeared; many of these migrants were very abundant 16 years earlier. Relative abundance has also decreased for most resident and migratory species that remained or visited the area. If uncontrolled urban expansion continues, we predict that the rate of extinction of the avifauna that originally inhabited this region would continue possibly increasing.     

Phytophthora andina sp. nov., a newly identified heterothallic pathogen of solanaceous hosts in the Andean highlands

A blight disease on fruits and foliage of wild and cultivated Solanum spp. was found to be associated with a new species of Phytophthora. The proposed novel species is named Phytophthora andina Adler & Flier, sp. nov. based on morphological characteristics, pathogenicity assays, mitochondrial DNA haplotyping, AFLP fingerprinting and nuclear and mitochondrial DNA sequence analyses. Isolates of P. andina (n = 48) from the Andean highland tropics of Ecuador were collected from 1995 to 2006. Phytophothora andina is closely related to P. infestans and has semipapillate, ellipsoidal sporangia borne on sympodially branched sporangiophores. It is heterothallic and produces amphigynous antheridia. The species consists of several clonal lineages, including the EC‐2 and EC‐3 RFLP lineages, which were described previously as P. infestans. Approximately 75% of isolates react as compatibility type A2 when paired with an A1 compatibility type isolate of P. infestans. However, when A2 isolates from the Anarrhichomenum section of Solanum were paired in all combinations, viable oospores were obtained in several crosses, suggesting that there is a unique compatibility interaction in P. andina that is complementary to that described in P. infestans. Nuclear and mitochondrial sequence analysis supported the species designation of P. andina. This newly identified heterothallic pathogen shares a common ancestor with P. infestans and may have arisen from hybridization events with sister taxa in the Andes.