Abstract:
The timber and pulp industry is an important part of the economy of Chile, and it relies on Pinus radiata plantations as its most important crop. For this reason it is crucially important to develop capacity and knowledge to deal with the ever increasing number of diseases of P. radiata, which represent one of the greatest threats to the sustainability of this industry. This thesis included investigations on the three main pathogens currently affecting P. radiata in nurseries (Fusarium circinatum and Phytophthora pinifolia) and in plantations (P. pinifolia and Neonectria fuckeliana) in Chile. Studies focused on issues such as correct identification, population diversity and epidemiology as important basic knowledge that will contribute towards the understanding of the pathogens and improved management decisions. Importantly, tools were developed to prove KochÕs postulates for P. pinifolia as the causal agent of DFP. Sporangia of this pathogen were shown to remain on the needles for extended periods of time and to mainly disperse during the rainy season. Important for the exportation of timber, it was shown that green sawn lumber taken from trees infected by P. pinifolia or from infected pine plantations displayed no evidence of the pathogen surviving in this material. Finally, the potential was demonstrated for combining data on site selection for planting, the use of disease-tolerant clones and the application of effective chemical products for the management of DFP as part of an integrated strategy. For F. circinatum, a population genetic study revealed a relatively low level of gene and genotypic diversity, including only one mating type, in Chilean populations. These data, together with the predominantly asexual reproduction of the pathogen, and demonstrated variation in resistance of the trees, illustrates the potential of resistance breeding strategies. It also illustrates the importance of quarantine to prevent the introduction of more diversity of the pathogen. Neonectria fuckeliana was confirmed to be the causal agent of flute canker across all the areas assessed. The knowledge generated through this thesis on key pathogens of P. radiata in Chile will form an important part of the knowledge foundation on which management decisions will be taken in future.