Effect of Bacillus subtilis on fruit yield and quality in Actinidia deliciosa orchards infected with bacterial canker in the north of Portugal

Bacterial canker of kiwifruit, caused by Pseudomonas syringae pv. actinidae (Psa), a disease included in the EPPO A2 List, has been registered in the north of Portugal since 2010. The relationship between the bacterium and cultural practices, namely the application of the biological control agent Bacillus subtilis in kiwifruit orchards in Portugal, is poorly understood. The most damaging phase of the disease occurs in winter and involves damage of the main vine structure and overwintering canes, and also in spring, during pollen spread, thus reducing subsequent yield and fruit quality. The main objective of this study was to evaluate the effect of B. subtilis Serenade Max® on kiwifruit yield and quality in infected orchards of different ages. Two orchards (Actinidia deliciosa ‘Hayward’) with typical symptoms of Psa were selected for yield and quality assays. Thirty plants were selected from the young orchard (6 years old) and other 30 plants were selected from the old orchard (30 years old), both located in Valença, northwest Portugal. This work showed that the use of B. subtilis as a biological control agent against Psa did not affect overall kiwifruit quality, namely the longitudinal and length diameters of fruit, the total soluble solids content, firmness, pH, titratable acidity and dry matter, but contributed significantly to increased yield in the younger orchard compared with the older orchard.info:eu-repo/semantics/publishedVersio

Efficacy of Bacillus subtilis for the control of Pseudomonas syringae pv. actinidiae under field conditions

Bacterial canker of kiwifruit, caused by Pseudomonas syringae pv. actinidiae (Psa), is a disease included on the EPPO A2 List because it is currently increasing in the Mediterranean region. Climatic conditions determine the multiplication and dispersal behavior of Psa and may influence its biological control (BC). However, information regarding the influence of climatic conditions on growth of the Psa bacterium in Portugal is scarce. The aims of this study were to relate the climatic conditions with the efficacy of Bacillus subtilis Serenade Max® in controlling the disease, to determine whether disease incidence increased over the growing season, and to monitor carry-over of disease from one season to the next. Two ‘Hayward’ orchards of Actinidia deliciosa of different ages, located in Valença, in the north of Portugal, were selected for BC assay. Thirty plants were randomly selected from a young orchard (6 years old) and another 30 plants from an old one (30 years old). Psa was identified and characterized by morphological, biochemical and molecular tests. The efficacy of B. subtilis was evaluated by disease incidence, and correlated to climatic conditions. A standardized leaf infection index (0-4 scale of symptoms) was used to determine disease severity. Monitoring of Psa symptoms was performed every 30 days, from June 2016 to April 2017. The severity of the disease decreased in the summer season, characterized by unfavorable conditions for Psa such as high temperatures and scarce precipitation. B. subtilis was partially effective in controlling Psa in the 6-year-old orchard, and showed no efficacy in the protection of leaves in the 30-year-old orchard. B. subtilis applied at flowering could be considered as a suitable solution for the control of Psa biovar 3 only for the new kiwifruit orchard (6 years old).info:eu-repo/semantics/publishedVersio

Rheological behavior of thermoreversible k-carrageenan/nanosilica gels

The rheological behavior of silica/κ-carrageenan nanocomposites has been investigated as a function of silica particle size and load. The addition of silica nanoparticles was observed to invariably impair the gelation process, as viewed by the reduction of gel strength and decrease of gelation and melting temperatures. This weakening effect is seen, for the lowest particle size, to become slightly more marked as silica concentration (or load) is increased and at the lowest load as particle size is increased. These results suggest that, under these conditions, the particles act as physical barriers to polysaccharide chain aggregation and, hence, gelation. However, for larger particle sizes and higher loads, gel strength does not weaken with size or concentration but, rather, becomes relatively stronger for intermediate particles sizes, or remains unchanged for the largest particles, as a function of load. This indicates that larger particles in higher number do not seem to increasingly disrupt the gel, as expected, but rather promote the formation of stable gel network of intermediate strength. The possibility of this being caused by the larger negative surface charge found for the larger particles is discussed. This may impede further approximation of neighboring particles thus leaving enough inter-particle space for gel formation, taking advantage of a high local polysaccharide concentration due to the higher total space occupied by large particles at higher loads.FCT - PTDC/QUI/67712/2006FEDE

Late Holocene natural and man induced environmental changes in Western Iberian coast: assessing forcing factors

The Western coast of the Iberian Peninsula stands as an interface between both the Atlantic and Mediterranean climatic influences and marine / fluvial conditions. The paper aims to assess the environmental changes in the last ca 6000 years (both natural and anthropogenic induced) using multiproxy analysis (geomorphological and sedimentological data, elemental and stable isotope content, microfossil assemblages, radiocarbon dating, and historical records) applied to an embayed coast. The results showed the prevalence of marine environment until 6272-6000 cal BP, but with fluvial infilling of the inner embayment, even before present sea level was reached (ca 4500-4000 cal BP). The influx of sediments was probably the result of the four recorded wet episodes (at modelled age cal BP (2σ): E1 – 6067-4770, E2 – 5806-4409, E3 – 5383-4088, and E4 – 4086-3905). These great sediment influxes along the previous 3000 years continues until 2110-1962 cal BP triggering the downstream migration of the river mouth, the development of a sand barrier coast and of a sheltered lagoon inside the palaeo-embayment.Afterwards the sedimentation rate (SR) reached high values (0.19-0.48 cmyr-1), as the result of Roman intervention in the drainage basin where pastures and local fires are recorded, together with an increasing dryness. A major disturbance is recorded in the Pollen Assemblages Zones (between PAZ II and PAZ III) and in the sediments around 1863-1706 cal BP (2σ), in the transition from the Roman Age to the Muslim invasion period, probably reflecting a hiatus in the sedimentary record. Onwards, SR reached 0.21-0.57 cmyr-1. Two major hydro marine episodes may have contributed to this fact: the latter is the Lisbon tsunami (1755 AD) while the former may reflect the 16th Century tsunamis or a great marine storm episode. An aeolian environment prevailed since then and the embayment was transformed into a dune field interrupted only by the narrow channel of the river whose mouth is often closed.info:eu-repo/semantics/publishedVersio