Hongos asociados al decaimiento del pinus halepensis en españataxonomía y variabilidad de gremmeniella abietina

Resumen

During the last years the decline of the Aleppo pine (Pinus halepensis Mill.) has become an emerging problem in Spain. Aleppo pine has been widely used for afforestation on the Iberian Peninsula because it is very adaptable to various environments. Many of these stands and nearby natural forests have been progressively declining in health. Abiotic and/or biotic factors may be involved in the decline, which some scientists also attribute to Climate Change. The main objective of this work was to determine the mycoflora associated with the decline of Aleppo pine. Towards this purpose, 55 P. halepensis stands widely distributed on the Iberian Peninsula were sampled. In addition, the distribution of Gremmeniella abietina in Aleppo pine was delineated. Once the geographic distribution of G. abietina within the Iberian Peninsula was established, its genetic structure and taxonomic status were was compared to other known European populations. In this thesis, several endophytes, saprotrophs and fungal phytopathogenic species were recorded. Overall, their distribution and incidence was influenced by abiotic conditions such as low temperature, which is one of the main limiting factors of the natural distribution of Aleppo pine. Furthermore, the diversity of fungal endophytes was relatively high and classes Dothideomycetes, Eurotiomycetes, Leotiomycetes, Pezizomycetes, and Sordariomycetes were represented by different species. The taxonomic study of G. abietina was carried out with the only population found to date, located in the provinces of Palencia and Valladolid. This study had two objectives: to ascertain the genetic variability of G. abietina, and secondly, to discern the genetic variability of fungal virus community found in G. abietina. Altogether, the results suggested that the Spanish isolates correspond to a highly differentiated population of G. abietina with origin in the biotype A, which in addition has an extremely low genetic variation. Spanish G. abietina isolates abundantly hosted double- stranded RNA (dsRNA) molecules whose molecular weights and banding patterns correspond to putative members of Totivirus, Partitivirus and Mitovirus, previously reported in other populations of G. abietina. The genus Mitovirus was especially relevant because two mitovirus species were identified. One species was similar to mitoviruses of biotype A, but the other one was similar to the only mitovirus strains found in biotype B. This is the first time that distantly related mycoviruses of a single genus appear in one population of G. abietina, which suggests that horizontal transmission of viruses could have occurred between biotype B and the Spanish population.