Occurrence in Italy and characteristics of lettuce downy mildew (Bremia lactucae) resistant to phenylamide fungicides

Control of lettuce downy mildew (Bremia lactucae) with phenylamide fungicides has failed in some intensive lettuce-producing areas in Northern Italy since Spring 1993. Before then, these chemicals and particularly metalaxyl, provided the best disease control. The sensitivity of Bremia lactucae isolates collected in such areas to metalaxyl was evaluated in the laboratory. These strains grew and sporulated profusely on lettuce seedlings treated with 100 and 200 ppm of metalaxyl, whereas sensitive control strains were completely inhibited when treated with fungicide concentrations ranging from 0.5–1 ppm. Thus in Italy occurrence of resistance to phenylamide fungicides in Bremia lactucae has also been demonstrated, as in almost all the countries where these chemicals were previously authorised. Subsequently, a demonstration of occurrence of resistance was made and the virulence pattern of several strains (resistant and sensitive to metalaxyl) was characterised using differential NL series containing the 13 DM resistant genes or R factors. The results suggest the occurrence of a new pathotype in Italy different from all the 16 NL Bremia lactucae races studied.     

Density estimates of rural dog populations and an assessment of marking methods during a rabies vaccination campaign in the Philippines

We estimated the population density of dogs by distance sampling and assessed the potential utility of two marking methods for capture-mark-recapture applications following a mass canine rabies-vaccination campaign in Sorsogon Province, the Republic of the Philippines. Thirty villages selected to assess vaccine coverage and for dog surveys were visited 1 to 11 days after the vaccinating team. Measurements of the distance of dogs or groups of dogs from transect lines were obtained in 1088 instances (N = 1278 dogs; mean group SIZE = 1.2). Various functions modelling the probability of detection were fitted to a truncated distribution of distances of dogs from transect lines. A hazard rate model provided the best fit and an overall estimate of dog-population density of 468/km² (95% confidence interval, 359 to 611). At vaccination, most dogs were marked with either a paint stick or a black plastic collar. Overall, 34.8% of 2167 and 28.5% of 2115 dogs could be accurately identified as wearing a collar or showing a paint mark; 49.1% of the dogs had either mark. Increasing time interval between vaccination-team visit and dog survey and increasing distance from transect line were inversely associated with the probability of observing a paint mark. Probability of observing a collar was positively associated with increasing estimated density of the dog population in a given village and with animals not associated with a house. The data indicate that distance sampling is a relatively simple and adaptable method for estimating dog-population density and is not prone to problems associated with meeting some model assumptions inherent to mark-recapture estimators.     

Evaluation of Feed Attractants in Juvenile Senegalese Sole,Solea senegalensis

The Senegalese sole, Solea senegalensis, is a flatfish with increasing interest in the European aquaculture. However, one of the main limitations found in this species is related to the scarce attraction to commercial aquafeeds, thus determining low feed intake in fish farms. The aim of this study was to evaluate four ingredients of marine origin (fish meal hydrolysate [FMH], polychaete meal [POM], mussel meal [MUM], and squid meal [SQM]) as potential attractants for juvenile Senegalese sole. Four experimental feeds containing 10% of the potential attractants, plus a control diet without these ingredients, were evaluated. A total of 150 fish were distributed into ten 40‐L tanks (duplicate tanks per feed). A Latin square design was carried out, and hence all the experimental diets were offered to each tank in successive periods of 7 d. Fish were fed twice a day (morning and afternoon), and the feeding behavior of the animals was assessed by direct observations. Behavioral pattern assessed was classified as distant orientation, near orientation, or continuation of intake. The acceptability index for each behavioral phase and experimental feeds used was established for each observation. No behavioral differences could be noticed between the morning and the afternoon feedings. FMH showed the greatest attractant potential than among the ingredients assessed, and consequently this ingredient yielded the higher feed intake rates. On the other hand, POM was not the best attractant for juvenile Senegalese sole.     

Pulmonary recruitment of neutrophils and bacterial clearance in mice inoculated with aerosols of Pasteurella haemolytica or Staphylococcus aureus.

Pulmonary alveolar macrophages are considered to be the main phagocytic cell of the pulmonary defense mechanism. However recent studies indicate that neutrophils may also participate in the defense against inhaled bacteria. The aim of this investigation was to study in mice the correlation between numbers of phagocytic cells in the bronchoalveolar space and the pulmonary clearance of bacteria. White mice were exposed to aerosols of Pasteurella haemolytica (n = 129) or Staphylococcus aureus (n = 129) in three different experimental replicates. Another group of mice (n = 22) was sham exposed to an aerosol of sterile phosphate buffered solution in a single replicate. Animals were sacrificed at various times postaerosolization. The numbers of neutrophils and alveolar macrophages in lung lavages and the pulmonary bacterial clearance rates were determined and statistically analysed. No significant differences (p greater than 0.05) were observed in the rates of pulmonary clearance between the two genera of bacteria, but P. haemolytica had a significant (p less than 0.05) replicate effect. The number of alveolar macrophages was not significantly affected by either bacteria or phosphate buffered solution. Exposure to P. haemolytica resulted in dramatic, significant (p less than 0.01) but transient increases in neutrophils in the bronchoalveolar space as well as a significant (p less than 0.01) increase in the weights of lung. The correlation between neutrophils and clearance was positive for P. haemolytica but negative for S. aureus. These results indicate that both species of bacteria are rapidly eliminated from the lung despite a rather different cellular response.     

Growth and Body Composition of Juvenile Hybrid Bluegill Lepomis cyanellus × L. macrochirus Fed Practical Diets Containing Various Percentages of Protein

Growth, survival, and body composition were evaluated in two feeding trials using juvenile hybrid bluegill Lepomis cyanellus × L. macrochirus . In Experiment 1, hybrid bluegill (20 g) were stocked into 1.25-m³ cages at a rate of 300 fish/cage and fed diets containing 35, 40, 44, or 48% protein for 12 wk. Fish meal comprised 32% of the dietary protein in all diets. Fish were fed all they could consume in 40 min. No significant differences ( P > 0.05) in individual length, individual weight, specific growth rate (SGR), condition factor (K), and feed conversion ratio (FCR) were found among treatments and averaged 13.4 cm, 47.4 g, 1.02%/d, 1.96, and 4.06, respectively. Whole-body composition of hybrid bluegill indicated that fish fed a diet containing 35% protein had a significantly lower ( P < 0.05) percentage protein (56.3%) and a higher ( P < 0.05) percentage lipid (29.3%) compared to fish fed diets containing 40, 44, and 48% protein. In Experiment 2, 15 hybrid bluegill (15 g) were stocked into 110-L aquaria and fed one of four diets containing 28, 32, 36, or 38% protein for 10 wk. Fish were fed twice daily all they would consume in 20 min. Fish fed a diet containing 38% protein had higher ( P < 0.05) percentage weight gain (265%) than fish fed diets containing 28% (203%) and 32% (219%) protein, but were not significantly different ( P > 0.05) compared to fish fed a diet containing 36% protein (251%). Feed conversion ratio (FCR) of hybrid bluegill fed diets containing 36% and 38% protein (average 1.39) were significantly lower ( P < 0.05) than fish fed a diet with 28% protein (1.73). Results from these studies indicate that hybrid bluegill can be fed a practical diet containing 35–36% protein (with fish meal comprising 32% of the protein). Further refinement of the diet formulation may allow producers to reduce diet and production costs.     

Changes in hydrophilic and lipophilic antioxidant activity and related bioactive compounds during postharvest storage of yellow and purple plum cultivars

Eight plum cultivars (four dark-purple and four yellow) were harvested at the commercial ripening stage, and changes of fruit quality properties were evaluated during cold storage and subsequent shelf-life, with special emphasis on bioactive compounds (phenolics, anthocyanins and carotenoids) and antioxidant activity (TAA). From the eight plum cultivars, four showed the typical climacteric ripening pattern (‘Blackamber’, ‘Larry Ann’, ‘Golden Globe’ and ‘Songold’) while four behaved as suppressed-climacteric types (‘Golden Japan’ ‘Angeleno’, Black Diamond’ and ‘TC Sun’), the latter being described for the first time. At harvest, large variations in phytochemicals and antioxidant activity were found among cultivars in peel and pulp tissues, although phytochemical concentration and antioxidant activity were higher in the peel than in the flesh (2–40-fold depending on the bioactive compound). During storage, increases in total phenolics for all cultivars (peel and pulp), in total anthocyanin content in the peel of the dark-purple plums, and total carotenoids in the peel and pulp of the yellow cultivars were observed. This behaviour of the bioactive compounds was reflected in TAA changes, since hydrophilic-TAA (H-TAA) was correlated with both phenolics and anthocyanins, while lipophilic-TAA (L-TAA) was correlated with carotenoids. L-TAA comprised about 30–50% of the TAA in plum tissues. Carotenoids and phenolics (and among them the anthocyanins) could be the main lipophilic and hydrophilic compounds contributing to L-TAA and H-TAA, respectively. No significant loss of bioactive compounds and TAA occurred during prolonged plum storage. Moreover, for a better evaluation of the antioxidant potential of plums, the contribution to carotenoids should not be overlooked.     

Afforestation trials with Prosopis chilensis (Mol.) Stuntz and Prosopis flexuosa D.C. in the Dry Chaco, Argentina

In implantation trials carried out with Prosopis chilensis and Prosopis flexuosa, the following variables were considered: implantation time (December and March), implantation technique (direct seeding and seedling transplantation) and age of the seedlings at the time of transplantation (60, 105 and 150 days). Survival was evaluated for more than 9 months after implantation and trials were repeated in 3 consecutive years.

Results from both species were similar and they show that survival after transplantation was higher (60–80%) than from direct seeding (35–45%). Survival from transplantation was independent of the size and age of the seedlings and it was less affected by climatic conditions than direct field sowing. Survival from direct seeding was higher in March than in December. The best time for either implantation alternative would be the end of the summer or beginning of fall, when climatic conditions increase the probability of seedling survival.     

Changes in understory species diversity during theNothofagus pumilio forest management cycle

Human commercial activities must be compatible with sustainable management to achieve species conservation in the natural environment. After harvesting, diversity and abundance of understory species differ substantially from the pre-harvest situation. Have knowledge of the changes that logging produces in all components of the system allows us to develop management alternatives with reduced impacts. The objective of this work was to evaluate changes in density, biomass and diversity of understory species along a forest shelterwood cut system management cycle in aNothofagus pumilio forest. Six forest management situations (postharvesting stands and different phases of forest development) were sampled in a pureN. pumilio forest of Tierra del Fuego (Argentina) of middle-high site class (fromclass I toIII). Species number, density and biomass were modified substantially after a shelterwood cut. These were being greatest after cutting and falling substantially when the forest canopy closes during theinitial growth phase, returning to values similar to this virgin forest when themature phase was reached. The impact of the forest management on understory species diversity is analyzed and discussed. The silvicultural practices applied toN. pumilio forest in Tierra del Fuego permit the introduction of alien flora to the system, and produce great changes during the forest management cycle. To Celina Matteri, Itatí Ferraro, and Rosa Kofalt for their aid in taxonomical identification. To Juan Manuel Cellini, Ricardo Vukasovic and Gregorio Martínez Pastur for their participation in the field work; and to the sawmillLos Castores, Universidad Nacional de la Patagonia Austral, Centro Austral de Investigaciones Científicas and Instituto Nacional de Tecnología Agropecuaria for the institutional and financial support.     

Winter photoinhibition in the field involves different processes in four co-occurring Mediterranean tree species

Photoinhibition was examined in four co-occurring Mediterranean evergreen tree species during two consecutive winters. In response to low temperatures and saturating light, Juniperus phoenicea L., Pinus halepensis Mill., Quercus coccifera L. and Q. ilex ssp. ballota (Desf.) Samp. exhibited marked chronic photoinhibition, indicated by low predawn maximal photochemical efficiency of photosystem II (PSII) (Fv/Fm). Low Fv/Fm values were correlated with high concentrations of xanthophyll cycle components (VAZ) and with the maintenance of high concentrations of zeaxanthin overnight (DPSpd). In all species, however, chronic photoinhibition was enhanced as the winter progressed in the absence of changes in DPSpd, suggesting cumulative damage toward the end of winter. Photoinhibition differed among species: P. halepensis always displayed significantly higher Fv/Fm values; and Q. coccifera had the lowest Fv/Fm values, showing a high sensitivity to the combination of high light and low temperatures. Differences among species were not fully explained by differences in the xanthophyll pool or its de-epoxidation state. Chronic photoinhibition overlapped with a dynamic photoinhibition as shown by the low values of photochemical efficiency of the open reaction centers of PSII at midday. Winter photoprotective strategies differed among species and may involve photoprotective mechanisms in addition to those associated with xanthophylls. The observed species-specific differences matched results obtained for the same species in summer; however, comparison of the two seasons suggests that the higher VAZ concentration observed in winter has an additional structural photoprotective role.     

Citrus response to salinity: growth and nutrient uptake

To determine the effects of salinity on relative growth rate (RGR), net assimilation rate on a leaf weight basis (NAR(w)), leaf weight ratio (LWR), and nutrient uptake and utilization of citrus, we grew four citrus rootstocks (sour orange, Cleopatra mandarin, Carrizo citrange and Citrus macrophylla) in nutrient solutions containing 0, 10, 20, 40 or 80 mM NaCl for 20, 40 or 60 days. For each element analyzed, specific absorption rate (SAR) and specific utilization rate on a leaf basis (SUR(L)) were calculated for the period between Days 40 and 60. Relative growth rate decreased with time for all treatments and rootstocks. Salt treatment significantly reduced both RGR and NAR(w), whereas LWR showed no definite trend. In all rootstocks, NAR(w), but not LWR, was significantly correlated with RGR, indicating that NAR(w) was an important factor underlying the salinity-induced differences in RGR among the citrus rootstocks. At Day 60, salinity had a significant effect on leaf concentrations of Cl, Na, K, Ca, Mg, P, Fe, Mn and Zn and on the SAR and SUR(L) of most elements. In general, RGR was correlated with SAR and SUR(L). Therefore, in addition to osmotic effects and the inhibitory effects of high concentrations of Cl(-) and Na(+), an imbalance of essential nutrients may also contribute to the reduction in plant growth under saline conditions.