Activity of foliar extracts of cultivated eggplants against sclerotinia lettuce drop disease and their phytochemical profiles

Antifungal activity of plant-derived compounds can be exploited in disease management systems to improve sustainability and replace synthetic molecules. In this study, four crude hydroethanolic extracts of leaves, collected from Italian Solanum spp. landraces, were selected to evaluate their ability to suppress Sclerotinia minor Jagger, a great threat to lettuce production worldwide. In vitro fungal development was inhibited by Solanum melongena L. and S. aethiopicum L. extracts showing a dose-dependent correlation. At the highest concentration tested in the current experiments (45 mg mL^?1) antifungal activity caused up to 90% growth reduction. The exposure of the fungus to S. aethiopicum extracts incited pronounced changes in the hyphal morphology as observed under light microscopy. Consistently, under laboratory conditions, in planta application of the active extracts on lettuce significantly reduced Sclerotinia drop disease in comparison to non-treated controls. Phytochemical composition was determined by liquid chromatography/mass spectrometry (LC/MS) analyses. Four secondary metabolites differentially present in the extracts, identified as n-caffeoylputrescine, chlorogenic acid, isoquercitrin and solasodoside A, are hypothesized to play a crucial role in mechanisms underlying biological effects of extracts. PCA analysis showed positive correlations of these compounds with the overall control ability of the extracts. The results indicated that foliar material from cultivated eggplant could be suitable to produce biological-based remedies for controlling plant diseases.     

Microparticles containing gallic and ellagic acids for the biological control of bacterial diseases of kiwifruit plants

Journal of Plant Diseases and Protection - Over the last decades, kiwifruit cultivation has gained increasing importance all over the world, but some bacterial diseases seriously threaten its...     

Constitutive expression of interferons in swine leukocytes

Interferon (IFN)-α and IFN-γ positive cells were revealed by flow cytometry in peripheral blood mononuclear cells (PBMC) of Specific Pathogen Free (SPF) pigs. A low prevalence of IFN-γ positive cells was also detected in PBMC of some Porcine Reproductive and Respiratory Syndrome virus-infected pigs and uninfected, control pigs. IFN-α positive cells showed phenotypes of both monocytes and plasmacytoid dendritic cells. The presence of IFN-α in PBMC was also confirmed by Western blotting. By immunoprecipitation, IFN-α was detected as 32 and 55-57 kDa bands in PBMC of healthy SPF piglets. These samples were also IFN-γ positive; the cytokine was revealed as 24, 37 and 54 kDa bands. The unusual molecular mass values of intracellular interferons were probably due to oligomerization, as previously described for human IFN-α. Swine intracellular IFN-α displayed the expected antiviral activity on bovine MDBK cells. The results indicate that interferons are constitutively expressed in swine leukocytes with peculiar molecular features.     

Soluble carbohydrates content in tomato pollen and its variations along and between blooming periods

The soluble carbohydrates content in the mature (starchless) pollen of the tomato (Solanum lycopersicum L.) cv. Platense was studied at several moments of the blooming period in two consecutive years. The aim of the analysis was to evaluate if the content of soluble carbohydrates is relatively constant or if it can fluctuate along the blooming period. No significant variations in pollen viability were recorded along each season. The soluble carbohydrates found and their concentrations can change significantly among samples, but the fluctuations observed did not follow a strongly definite pattern in any season. Reducing sugars predominated; small quantities of a phosphorylated sugar, UDP-glucose, and maltosaccharides were also recorded. The constant presence of maltosaccharides is a novel record for pollen. Sucrose was absent in one season, but present in the other, in low percentages in contrast to reducing sugars. Changes in the soluble carbohydrates content have been usually related with alterations in pollen fertility. However, there may be some flexibility in the metabolism of the pollen studied this time, at least within a certain range, which may allow constant adjustments to maintain acceptable levels of viability despite the variations in the carbohydrates concentrations.     

A strawberry disease caused by Acremonium strictum

We report Acremonium strictum as the causal agent of a new disease in strawberry plants (Fragaria x ananassa Duch.) in the Northwest of Argentina. Both the structure of conidiophores and the sequence spanning the internal transcribed spacers 1 and 2 (ITS1 and ITS2) of the nuclear ribosomal DNA (rDNA) allowed confirming the affiliation of the isolate, corresponding to A. strictum. An analysis of symptoms and lesions caused by the strain of A. strictum in susceptible cultivars showed that the typical symptoms are as follows: in an early stage, small necrotic light-brown spots in leaves and petioles increase in number and size as the disease progresses; in a more advanced stage, dark necrotic areas expand over petioles and leaves causing strangulation of petioles and the plant wilt. Crown rot was not observed even at a very advanced stage of the disease.     

Perspectives on the use of a seaweed extract to moderate the negative effects of alternate bearing in apple trees

Summary

Alternate bearing is a serious problem in many apple varieties. In fact, each year, apple trees have to be thinned in order to ensure a correct and constant balance between the reproductive and vegetative tendencies of the plant. In organic fruit growing, there is no alternative to the expensive and time-consuming process of hand-thinning. Under these conditions, the use of natural bio-stimulants which enhance the efficiency of nutrient uptake, plant fitness to different pedoclimatic conditions, and plant tolerance to stress, offers new opportunities to reduce the negative effects of alternate bearing. The aim of this work was to evaluate the effects of Actiwave^®, a metabolic enhancer derived from the alga, Ascophillum nodosum, on ‘Fuji’ apple trees affected by experimentally-imposed alternate bearing. The experiments were carried in open field conditions over four consecutive years. Although the effect of Actiwave^® was erratic from year-to-year, the compound generally reduced those problems linked to alternate bearing. Actiwave^® had its most significant effect on alternate bearing plants that were also affected by nutrient deprivation due to the absence of fertilisation. In these trees,Actiwave^® decreased the oscillations in yield between “on” and “off” years and increased the average fruit weight on plants affected by too-high a crop load. Treated trees also showed higher leaf chlorophyll contents (increased by 12%), with a consequent increase in the rates of photosynthesis and respiration. On the other hand, under standard conditions, in well-fertilised balanced plants, Actiwave^® did not have any significant effect. This evidence corroborates the hypothesis that Actiwave^® may be a useful tool to reduce alternate bearing in organic and low-input farming.     

Epidemiological survey of Border disease virus among sheep from northern districts of Japan

The first epidemiological survey of Border disease virus (BDV) was undertaken in small ruminants in Japan. Ovine sera, collected from the northern prefectures of Hokkaido, Aomori and Iwate, were examined for the presence of antibodies against BDV using the neutralization peroxidase-linked antibody test. Twenty-nine (17.6%) of one hundred and sixty-five samples were seropositive for BDV. Results were specific, excluding cross-reactions with bovine viral diarrhea virus (BVDV). Only one sample (0.6%) was positive for BVDV, and was negative for BDV. Despite serological evidence of virus circulation, there have been no clinical cases of border disease in sheep in Japan. Although no diagnostic measures were performed, the infection did not appear to be associated with a reduction in ewe fertility nor with lamb mortality.     

Comparative evaluation of PRRS virus infection in vaccinated and naïve pigs

The purpose of this study was to evaluate the time-course of the immune response to a field Porcine Respiratory and Reproductive Syndrome virus (PRRSV) strain in PRRS-naïve, untreated pigs, as well as in four groups of age and breed-matched pigs injected with a live attenuated PRRS vaccine, its adjuvant, an inactivated PRRS vaccine and an irrelevant, inactivated Porcine Circovirus type 2 (PCV2) vaccine, respectively. PRRSV infection was confirmed in all groups by PCR and antibody assays. The antibody response measured by ELISA took place earlier in pigs injected with the live attenuated vaccine, which also developed a much stronger serum-neutralizing antibody response to the vaccine strain. Yet, no clear protection was evidenced in terms of viremia against the field virus strain, which showed 11.1% nucleotide divergence in ORF7 from the vaccine strain. In vitro, the interferon (IFN)-γ response to PRRSV was almost absent on PVD 60 in all groups under study, whereas the prevalence of interleukin (IL)-10 responses to PRRSV was fairly high in PCV2-vaccinated animals, only. Results indicate that distinct patterns of immune response to a field PRRSV strain can be recognized in PRRS-vaccinated and naïve pigs, which probably underlies fundamental differences in the development and differentiation of PRRSV-specific immune effector cells.