Chestnut tree productive stands in catalonia: improvement of sanitary management of fistulina hepatica and cryphonectria parasitica
- Autores: Andreu Meijer Mora
- Directores de la Tesis: Carlos Colinas González (dir. tes.), Emigdio Jordan Muñoz Adalia (codir. tes.)
- Lectura: En la Universitat de Lleida ( España ) en 2024
- Idioma: español
- Tribunal Calificador de la Tesis: Julio Javier Díez Casero (presid.), Cristina Vega García (secret.), Carmen Romeralo Tapia (voc.)
- Programa de doctorado: Programa de Doctorado en Gestión Forestal y del Medio Natural por la Universidad de Lleida
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Sweet chestnut (Castanea sativa Mill.) is a high-value forest species that during the last century has faced different threats that led to a generalized silvicultural abandonment in north-east Spain since the 1980s. The main cause of its decline is the appearance of the exotic disease known as chestnut blight [causal agent: Cryphonectria parasitica (Murrill) M.E. Barr; Diaporthales, Cryphonectriaceae] and uncertain market conditions. This disease is a major concern for chestnut forestry in Europe. The fungus colonizes vascular tissues and develops generating cankers causing severe dieback and, in some cases, the death of the tree. In the 1990s chestnut red stain (CRS) became another concern for sweet chestnut coppice managers. CRS is a heartwood discoloration caused by the fungus Fistulina hepatica (Schaeff.) With. (Agaricales, Fistulinaceae) that at early stages does not seem to affect the structural properties of wood. Still, the timber's economic value drops up to 70%. In order to improve the sanitary management of chestnut productive stands, the following objectives were defined for this doctoral thesis: i) to evaluate the tolerance to chestnut blight of 28 genotypes and 10 progenies of C. sativa from a Spanish local population (Montseny-Northeast of Catalonia) in excised shoots (Objective I); ii) to determine if different thinning intensities in managed chestnut stands influences the occurrence of F. hepatica (Objective II); iii) characterize with a resistograph the resistance of F. hepatica-infected and free C. sativa heartwood (Objective III).
For the objective I, the tolerance to chestnut blight was evaluated on excised and debarked well lignified shoots in a genetic breeding program of this species. A total of 28 C. sativa genotypes and 10 progenies were inoculated with C. parasitica wild strain, monitoring the degree of colonization of the tissue for 6 days. Results showed a total of nineteen genotypes (70%) and four progenies (40%) with a susceptibility to chestnut blight not significantly different from Castanea mollissima. These results provide an approximation of the genetic potential of local C. sativa to gain a significant resistance to C. parasitica similar to that of other species that have coevolved with this pathogen. These results will be incorporated at the genetic improvement program for this species. For objective II, the effects of different forest management strategies (i.e low thinning, selective mixed thinning, and no intervention) and stand characteristics on the occurrence of F. hepatica in chestnut coppice stands were evaluated. Stand characteristics were measured seven years after the last intervention and the incidence of F. hepatica was evaluated through molecular methods on 75 trees. Data modeling revealed the significant effect of the quadratic mean diameter before the interventions as explanatory factor of the incidence of F. hepatica. Our results also suggest that the time of intervention is more important than the type or intensity of the thinning itself regarding the percentage of fungal infection. Thinning at earlier stages seemed to reduce the incidence of F. hepatica. For the objective III, resistography was used to characterize the wood and determine the density variation between healthy and F. hepatica infected trees. Thirteen wood-quality indexes were calculated and their correlation with the presence of the pathogen was evaluated using generalized linear mixed models. We found clear differences between healthy and diseased trees in four indexes: average of maximums, average of minimums, maximum variation and minimum value. The results support the hypothesis that, although CRS does not seriously impact the wood properties at early stages, it modifies them enough that its presence can be detected through inexpensive and fast mechanical methods. Based on these results, a new resistographic index was designed that allows foresters to estimate the risk of tree infection early in the rotation without the need for felling the trees.
The results presented in this thesis offer new insights aimed to provide forest managers with information about less susceptible genotypes of C. sativa to C. parasitica. Additionally, this work provides new guidance and tools to evaluate the incidence of CRS, targeting thinnings adjusting rotations accordingly and to mitigate the economic incidence of F. hepatica's infection.
