The secondary metabolites profile of Stemphylium lycopersici, the causal agent of tomato grey leaf spot, is complex and includes host and non-host specific toxins
AUSTRALASIAN PLANT PATHOLOGY
Authors: Medina, Rocio; Franco, Mario E. E.; da Cruz Cabral, Lucia; Bahima, Jose Vera; Patriarca, Andrea; Balatti, Pedro A.; Saparrat, Mario C. N.
Abstract
The aim of this work was to characterize the secondary metabolite (SMs) profile of Stemphylium lycopersici, a necrotrophic fungus that causes the disease known as grey leaf spot. We detected twenty-four SMs in cultures of S. lycopercisi within the extracts of 19 isolates. Each of them presented a characteristic unique profile. While highly virulent isolates synthesized a high number of metabolites (15), the low virulent ones synthesized a low number of SMs (2). However, a PCA analysis could not establish the relationship between SMs and virulence. Infectopyrone was the most frequent metabolite produced by the isolates (89%).
Reconstruction of 7500 years of coastal environmental change impacting seagrass ecosystem dynamics in Oyster Harbour (SW Australia)
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
Authors: Kaal, Joeri; Lavery, Paul S.; Martinez Cortizas, Antonio; Lopez-Costas, Olalla; Buchaca, Teresa; Salinas, Cristian; Serrano, Oscar
Abstract
Seagrass ecosystems, which have important functions such as coastal protection and blue carbon sequestration, are threatened by anthropogenic pressure including climate change. Long-term data series from seagrass sedimentary archives (mats) can be used to understand natural cycles of environmental change and answer key questions related to contemporary management. A 7500 yr sediment record from Posidonia australis meadows in Oyster Harbour (Albany, SW Australia) was subjected to multiproxy reconstruction by means of pigment analysis (UHPLC), analytical pyrolysis (Py-GC-MS), carbonate content, delta C-13 and delta N-15 stable isotope ratios, organic C (C-org) content, C-org/N ratio and glomalin-related soil proteins (GASP). The study revealed a brackish lagoon (7500-7000 cal yr BP) that was transformed in an open marine environment (7000-4100 cal yr BP) due to Holocene transgression. Earliest evidence of seagrass establishment was detected around 4500 cal yr BP, and meadow extension accelerated between 4100 and 3700 cal yr BP. The meadow environment was surprisingly resistant against environmental perturbations, as the mat, composed of P. australis seagrass fibres embedded within a siliciclastic mineral matrix containing biogenic carbonates, continued to develop steadily until 190 cal yr BP (1830 CE). Then, shifts in several proxies (pigments, GASP) showed evidence of terrestrial runofftriggered eutrophication/turbidity (likely driven by forest clearance and agricultural activities after European settlement), but the seagrass showed resilience (no decline of the proportion of seagrass-derived C-org). By contrast, since similar to 1930 CE seagrass retreat is evident in the biogeochemical record: lighter delta C-13 values, lower lignin abundance and shifts in pigment abundance and types, affecting the balance between seagrass inputs and alternative sources, as was observed in previous studies of the area. The findings show that pigment proxies are useful early indicators of shifts in seagrass ecosystem condition, while lignocellulose and other pyrolysis products are useful proxies of more profound ecosystem alterations that influence seagrass abundance. The record indicates that the climax seagrass ecosystem condition, which prevailed for several millennia, had been impacted over the last century. Management of seagrass and coastal ecosystems should aim to avoid crossing ecological thresholds and diminish local impacts aggravating those of global change.