Nitrogen balance and losses through drainage waters in an agricultural watershed of the Po Valley (Italy)

Sustainable agriculture requires assessments of nitrogen fluxes and monitoring of potential nitrate losses. Watershed studies are particularly valuable to calculate nitrogen balances and quantify the relative importance of different sources of inputs and outputs. A nitrogen balance was calculated from September 2004 to October 2006 in an agricultural watershed named Valle Volta (Northern Italy) located in a Nitrate Vulnerable Zone. The area, consisting of 17.4 km² of arable land, with limited presence of urban areas and roads, is entirely below the sea level (3 m b.s.l. in average). Soils are typically Vertic Cambisols and Thionic Fulvisols with fine texture (silty clay or silty clay loam). About 45% of the agricultural soil is pipe-drained. The ground water level is maintained at 4.6 m b.s.l. by the activity of pumps that raise excess waters into a river. Water fluxes in and out from the basin were daily registered, and dissolved inorganic nitrogen concentration (N–NO₃ + N–NH₄) analyzed periodically. Data about fertilizers applications, seeds and crop yield were obtained from farmers’ interviews. Biological nitrogen fixation (BNF) was estimated on the base of dry matter yield. Major N inputs derived from fertilizers (174–188 Mg watershed⁻¹ year⁻¹), followed by BNF (126–131 Mg watershed⁻¹ year⁻¹). Maize was the crop receiving the highest fertilization rates, accounting for more than 40% of total fertilizer inputs. Saleable products were the main form of N leaving the watershed (317–338 Mg watershed⁻¹ year⁻¹). Nitrate was the main N form in irrigation and efflux water; its concentration was higher from autumn to spring, with peaks of 10–20 mg N L⁻¹ in efflux water, while it was low in summer. Nitrogen losses with efflux water were higher in spring and in autumn. Overall, losses of nitrate by efflux water were limited if compared with literature data. Water balance in the area remained near zero at the beginning and the end of the first year, confirming the suitability of the area for this kind of study. The potential net contribution of each hectare of agricultural soil of Valle Volta basin to the N load toward the Adriatic sea is about 5.5 kg N. Our study demonstrated that in the Valle Volta watershed, total N outputs and inputs are of similar magnitude, indicating that crop management and especially N fertilization techniques has reached good levels of ecological sustainability.     

Effects of leaf scales of different pineapple cultivars on the epiphytic stage of Fusarium guttiforme

The fungus Fusarium guttiforme (Syn. F. subglutinans f. sp. ananas) is responsible for fusariosis, one of the main phytosanitary threats to pineapple (Ananas comosus var. comosus). A structural study comparing epidermal differences in pineapple cultivars resistant and susceptible to fusariosis was performed, relating properties of the epidermis to known susceptibility to the disease. The basal, non-chlorophylled, portions of mature leaves of pineapple plants were analyzed by light and electron microscopy. All cultivars showed common morpho-anatomic aspects characteristic of Bromeliaceae, such as scutiform scales and unstratified epidermis. However, cultivar Vitoria (resistant) had less scales than cultivars Smooth Cayenne (susceptible, intermediate severity) and Perola (susceptible, with extreme severity of fusariosis symptoms). Inoculation of conidia suspension (10⁵ conidia ml⁻¹) of the fungus F. guttiforme to leaves and harvesting 24 h later yielded numbers of viable colonies related to the density of leaf scales. This suggests that scales can act as havens for fungal conidia and favour the epiphytic stage of the fungus on pineapple plants, and are involved in the interaction of plant and pathogen. A reduction in scale numbers was related to lower infection levels and is relevant to the future breeding programme for development of new pineapple cultivars resistant to fusariosis and their involvement in integrated control strategies.     

Skeletal anomaly assessment in diploid and triploid juvenile Atlantic salmon (Salmo salar L.) and the effect of temperature in freshwater

Triploid Atlantic salmon tend to develop a higher prevalence of skeletal anomalies. This tendency may be exacerbated by an inadequate rearing temperature. Early juvenile all‐female diploid and triploid Atlantic salmon were screened for skeletal anomalies in consecutive experiments to include two size ranges: the first tested the effect of ploidy (0.2–8 g) and the second the effect of ploidy, temperature (14 °C and 18 °C) and their interaction (8–60 g). The first experiment showed that ploidy had no effect on skeletal anomaly prevalence. A high prevalence of opercular shortening was observed (average prevalence in both ploidies 85.8%) and short lower jaws were common (highest prevalence observed 11.3%). In the second experiment, ploidy, but not temperature, affected the prevalence of short lower jaw (diploids > triploids) and lower jaw deformity (triploids > diploids, highest prevalence observed 11.1% triploids and 2.7% diploids) with a trend indicating a possible developmental link between the two jaw anomalies in triploids. A radiological assessment (n = 240 individuals) showed that at both temperatures triploids had a significantly (P < 0.05) lower number of vertebrae and higher prevalence of deformed individuals. These findings (second experiment) suggest ploidy was more influential than temperature in this study.     

Arrangement of the Branches of the Aorta Abdominalis in the Wood Mouse (Apodemus sylvaticus)

Data on the distribution and variation of the abdominal arteries in the wood mouse, Apodemus sylvaticus, are given. Seventy specimens (44 males and 26 females) caught in the field were analyzed by injection of green latex solution and dissection. The general branching pattern of the aorta abdominalis is similar to those described in other rodents. There are certain differences, however, especially in the branching of the coeliac trunk, the origin of the genital arteries and the arrangement of the caudal mesenteric artery. Significant variability was detected in the distribution of the iliolumbar arteries about the testicular and ovaric arteries. Based on the observations and measurements carried out, some branching patterns of the aorta abdominalis are presented.     

Importance of cucurbits in the epidemiology of Papaya ringspot virus type P

Papaya ringspot virus type P (PRSV‐P) systemically infects Carica papaya and species belonging to the family Cucurbitaceae. Attempts to recover PRSV‐P from naturally infected cucurbit plants grown near or among diseased papaya trees have shown conflicting results worldwide. This study aimed to evaluate the natural infection of cucurbit species grown among and near papaya trees infected with PRSV‐P in Brazil. Natural infection of cucurbits with PRSV‐P occurred in zucchini squash but not in watermelon and cucumber. However, several attempts to recover PRSV‐P from numerous Cucurbita pepo cv. Caserta (zucchini squash) plants grown 5–80 m from diseased papaya trees in the field failed. Mechanical inoculations of Cucurbita pepo cv. Caserta, Cucurbita maxima cv. Exposição (pumpkin), Cucumis sativus cv. Primepack Plus (cucumber) and Citrullus lanatus cv. Crimson Sweet (watermelon) with five Brazilian PRSV‐P isolates showed that zucchini squash was the most susceptible species followed by watermelon and cucumber, while pumpkin was not infected. The results confirmed the variable susceptibility of cucurbit species to experimental and natural PRSV‐P infection. Given these facts, the control of the disease through roguing should focus mainly on diseased papaya plants, as has been practised successfully in Brazil for many years, and on those cucurbits particularly known to be susceptible to natural infection with PRSV‐P.     

The use of homologous antigen in the serological diagnosis of brucellosis caused by Brucella melitensis

In the European Union the serological diagnosis of brucellosis caused by Brucella melitensis is performed using the heterologous antigen of B. abortus S99. The possible higher sensitivity or ability of an early detection of antibodies by a homologous antigen may prove very useful in the final phases of an eradication programme. Results obtained in sheep experimentally infected by B. melitensis biovar 3 were compared using B. abortus S99, B. melitensis M1, M2 and M3 antigens in the Rose Bengal plate test (RBPT), the complement fixation test (CFT) and an enzyme-linked immunosorbent assay (ELISA) test. Forty-six sheep from an officially brucellosis-free flock were experimentally infected intraconjunctivally with B. melitensis biovar 3. Prior to infection, all animals were tested first against Brucella antibodies, weekly for 2 months post-infection (PI) and then monthly for a further 7 months. All sera were tested against the antigens listed above using RBPT, CFT and ELISA. Using a Bayesian approach, test sensitivities were estimated and compared. Their ability for the early detection of antibodies was evaluated through a regression model based on a logit response model, using the number of days PI as the independent variable and the logit of the fraction of positive animals as the dependent variable. No significant differences were detected among the various antigens used, either in terms of sensitivity or in terms of antibody kinetics; however, the CFT was significantly less sensitive than the RBPT and ELISA and it also showed a lower rate of increase of percentage positive animals (beta-coefficient of regression analysis).     

Effects of replacing rye-grass (Lolium spp.) hay by banana (Musa acuminata L.) by-products on feed intake,growth, and feed conversion rate of Canary hair sheep breed (Pelibuey) lambs

Tropical Animal Health and Production - The objective of this study was to evaluate the effects of replacing rye-grass (Lolium spp.) hay with banana (Musa acuminata L.) by-products on feed intake,...     

Zingiberene-mediated resistance to the South American tomato pinworm derived from Lycopersicon hirsutum var. hirsutum

The Lycopersicon hirsutum var. hirsutum accession PI 127826 is recognized as a good source of resistance to arthropod pests due to the action of the allelochemical zimgiberene, a sesquiterpene present in its glandular trichomes. Five genotypes were selected from the F₂ generation of the interspecific cross Lycopersicon esculentum ‘TOM-556’ × Lycopersicon hirsutum var. hirsutum ‘PI 127826’, based on their low levels (BPX-368-clone#56) or high levels(BPX-368-clone#92, BPX-368-clone#105,BPX-368-clone#179, BPX-368-clone#250) of zingiberene. The five F₂ genotypes were tested for resistance to the South American tomato pinworm Tuta absolutaalong with accession L. esculentum ‘TOM-556’ (pinworm susceptible), and the accessions L. hirsutum var. hirsutum ‘PI 127826’ and L. pennellii ‘LA716’ (resistant). The F₂ clones selected for high foliar zingiberene levels showed lower scores for leaflet lesion type(LLT), percent leaflets attacked (PLA) and overall plant damage (OPD) than the low zingiberene genotypes. The results indicated that zingiberene mediates resistance to the South American pinworm, based on feeding and on ovipositing deterrence, in populations derived from the interspecific cross between Lycopersicon. esculentum and Lycopersicon hirsutum var. hirsutum. Indirect selection for high foliar zingiberene content is suggested as an efficient technique for breeding tomatoes for resistance to the South American tomato pinworm. This revised version was published online in July 2006 with corrections to the Cover Date.