During extensive surveys for Phytophthora associated with alder mortality in western Spain, isolates were consistently recovered from necrotic bark of the collar and lower stem of Alnus glutinosa. Morphological and molecular... more
During extensive surveys for Phytophthora associated with alder mortality in western Spain, isolates were consistently recovered from necrotic bark of the collar and lower stem of Alnus glutinosa. Morphological and molecular characteristics of the selected isolates together with their physiology were examined. Morphologically, the isolates were homothallic and characterized by abundant production of terminal oogonia predominantly with two-celled amphigynous antheridia exhibiting ornamentation. Simple sporangiophores were observed bearing terminal, non-papillate, ellipsoid to ovoid sporangia. Colony growth patterns developed on V8 juice agar (V8A), carrot agar (CA), corn-meal agar (CMA) and potato-dextrose agar (PDA) showed uniform, radial or irregular growth patterns with appressed and/or woolly morphology. Temperature (2 °C, 5 °C, 10 °C, 15 °C, 20 °C, 25 °C, 27 °C, 30 °C and 32 °C), pH (5, 7, 9 and 11) and osmotic potential (−0.6, −1.2, −1.8 and −2.4MPa) significantly influenced radial mycelial growth of the isolates under laboratory conditions. Molecular analyses including ITS DNA region sequencing and subspecies specific primers amplification confirmed identification of the isolates as Phytophthora alni ssp. alni.
Further research is under way to carry out more surveys in order to determine the extent of damage and severity of the disease in different regions of Spain.
Further research is under way to carry out more surveys in order to determine the extent of damage and severity of the disease in different regions of Spain.
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Natural regeneration faces increasing difficulties in dry forests from the Mediterranean basin, including for normally well-regenerating species such as maritime pine (Pinus pinaster Aiton). In this paper, we studied female fertility,... more
Natural regeneration faces increasing difficulties in dry forests from the Mediterranean basin, including for normally well-regenerating species such as maritime pine (Pinus pinaster Aiton). In this paper, we studied female fertility, seed dispersal and spread rates in P. pinaster from the Spanish Northern Plateau, where natural regeneration failure is a main concern for forest managers. For this purpose we periodically collected data from seed traps and trees located at two core locations across several years. We found significant variation in interannual cone production, with the best seed trees being the same across years. In addition, we found highly skewed distributions of female reproductive effort and large fertility differences across stands located few kilometres away. Annual seed dispersal kernels fitted lognormal or 2Dt models depending on the stand analysed, with median dispersal distances between 14 and 25 m.
Kernels fitted for maximum dispersal periods showed an outstanding intraseasonal variation of median dispersal distances, from 10 to 54 m, in association to variable patterns of rainfall and maximum wind speed. The amount of seed produced appeared to be enough to guarantee the natural regeneration of the stands during the typical 20-year regeneration period. Colonisation simulations concluded that Mediterranean maritime pine has a notable dispersion capacity, which is strongly influenced by levels of fecundity and, especially, by the number and frequency of long-distance dispersal events. The latter play a key role in tree dispersion processes through enlarging the occupied area and fostering the invasion of abandoned crop land.
Kernels fitted for maximum dispersal periods showed an outstanding intraseasonal variation of median dispersal distances, from 10 to 54 m, in association to variable patterns of rainfall and maximum wind speed. The amount of seed produced appeared to be enough to guarantee the natural regeneration of the stands during the typical 20-year regeneration period. Colonisation simulations concluded that Mediterranean maritime pine has a notable dispersion capacity, which is strongly influenced by levels of fecundity and, especially, by the number and frequency of long-distance dispersal events. The latter play a key role in tree dispersion processes through enlarging the occupied area and fostering the invasion of abandoned crop land.
