Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Fungal diseases of trees are serious impediments to forest expansion and productivity. While the adverse effects of diseases of non-native plantation forest trees are increasingly recognized in Africa, the health of native trees has been virtually ignored. This is especially acute as many commercially propagated trees are related to native woody plants and recurrent movement of pathogens between native and non-native trees is increasingly being recorded. The genus Terminalia accommodates important indigenous tree species in Africa that provide a variety of valuable wood and non-wood products. Despite the importance of Terminalia spp., very little information has been recorded on their health problems. Research for this dissertation aimed at studying some of the fungal diseases of native and non-native Terminalia species in Africa. Special reference was provided to fungi in the Botryosphaeriaceae, a group of pathogens that infect host plants without always producing clear symptoms. A literature review, presented in Chapter One, highlighted the limited information available on the pathogens and pests associated with these trees. Most disease reports include minimal detail. Often the causal agents had been identified based only on morphology and were not classified to the species level. Studies performed in chapter two compared the assemblages of endophytic species of the Botryosphaeriaceae from T. catappa in Cameroon, South Africa and Madagascar. Five species were identified and two of these are new to science and provided with the names N. batangarum and L. mahajangana. The assemblage of the Botryosphaeriaceae varied from one country to another, however, colonization patterns in the three areas were similar. Greenhouse inoculation trials performed on young T. catappa trees showed variation among isolates tested, with L. pseudotheobromae being the most pathogenic. Chapter three represents the first investigation of the Botryosphaeriaceae on native Terminalia trees in Cameroon and Africa. Morphological and DNA sequence data were used to identify these species as L. theobromae, L. pseudotheobromae, L. parva and E. endophytica. Pathogenicity trials performed on young T. mantaly and T. catappa trees revealed that L. pseudotheobromae was the most virulent species. In chapter four, species of Botryosphaeriaceae on native Terminalia spp. in Southern Africa were studied. Nine species were identified from T. sericea and T. sambesiaca. Seven of these, L. crassispora, L. pseudotheobromae, D. alatafructa, P. olivaceum, N. parvum, N. kwambonambiense and N. vitifusiforme represented previously described species and two, L. cryptotheobromae and N. terminaliae, were described as new. The genetic analyses of populations of L. theobromae and L. pseudotheobromae presented in chapter five showed clear genetic divergence between L. theobromae and L. pseudotheobromae supporting their distinction as separate species. Both L. theobromae and L. pseudotheobromae populations possessed high gene diversity, moderate degrees of genotypic diversity, and high levels of gene flow between isolates from T. cacao and Terminalia spp. Both sexual and asexual modes of reproduction were found. The last chapter of this dissertation presents the description of a new genus in the Cryphonectriaceae, Aurifilum marmelostoma, using a combination of molecular and morphological tools. This fungus is the second genus in this family described from Terminalia spp. Pathogenicity tests conducted to assess its ability to cause disease revealed that the fungus is a possible pathogen of this tree. An extensive number of potentially pathogenic fungi, including five new species were found associated with native and non-native Terminalia spp. in Africa. As some of these fungal species could serve as sources of inoculum onto economically important crops, research presented in this dissertation provides a foundation for understanding health issues affecting Terminalia and related genera in selected regions in Africa. Hopefully, results of this study will serve as valuable tools in forestry management in Africa. Copyright / Thesis (PhD)--University of Pretoria, 2010. / Plant Production and Soil Science / Unrestricted

Research focused on the reduction of uncertainties when considering the wind resource in the vicinity of forestry. This thesis examined the use of high density laser scanning technology to capture the structure of forest canopies along with the measurement of thermal effects using sonic anemometry. Methodologies were then developed to include these high quality data in Computational Fluid Dynamics software in order to allow the complex nature of forestry flows to be considered analytically.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 8 uppsatser.

Lic.-avh. (sammanfattning) Alnarp : Sveriges lantbruksuniv., 2003. / Härtill 3 uppsatser.

Diss. (sammanfattning). Umeå : Sveriges lantbruksuniversitet, 2005. / Härtill 5 uppsatser.

Forest trees represent a unique group of organisms combined with ecological and economic importance. Owing to their random mating system and widespread geographical distribution, they harbor abundance genetic variation both within and among populations. Despite their importance, research in forest trees has been underrepresented majorly due to their large and complex genome and scarce funding. However, recent climate change and other associated problems such as insect outbreaks, diseases and stress related damages have urged scientists to focus more on trees. Furthermore, the advent in high-throughput sequencing technologies have allowed trees to be sequenced and used as reference genome, which provided deeper understanding between genotype and environment. Whole genome sequencing is still not possible for organisms having large genomes including most tree species, and it is still not feasible economically for population genomic studies which require sequencing hundreds of samples. To get around this problem, genomic reduction is required. Sequence capture has been one of the genomic reduction techniques enabled studying the subset of the DNA of interest. In this paper, our primary goal is to outline challenges, provide guidance about the utility of sequence capture in trees, and to leverage such data in genome-wide association analyses to find the genetic variants that underlie complex, adaptive traits in spruce and pine, as well as poplar. Results of this research will facilitate bridging the genomic information gap between trees and other organisms. Moreover, it will provide better understanding how genetic variation governs phenotype in trees, which will facilitate both marker assisted selection for improved traits as well as provide guidance to determine forest management strategies for reforestation to mitigate the effects of climate change. / Ph. D. / Forests are under extensive threat including increased demand in wood consumption, climate changes and associated diseases and stress related damages. Up until very recently, researches in trees have been relatively slower owing to their large and complex genomes. However, this has dramatically changed mainly due to the advancement in sequencing technology. There have been more and more studies performed identifying novel genes that are responsible for improved characteristics. In this study, we provided guidance about how to better utilize sequencing technology and identified genes that are potentially related with adaptation in trees.

The relative weights on individual trees in a biweight site chronology can indicate the consistency of tree growth responses to macroclimate and can be the basis for stratifying trees in climate-growth analyses. This was explored with 45 years of ring-width indices for 200 trees from five even-aged jack pine (Pints banksiana Lamb.) stands. Average individual-tree relative weights were similar, but most trees had at least one transient occurrence of low relative weight. The standard deviations of individual-tree relative weights suggested that some trees had mom variable growth responses than others. The trees were classified by the average and standard deviation of their relative weights, and biweight site chronologies were then calculated for these subgroups. Chronologies derived from trees with low average weights, and from trees with high standard deviation of weights, sometimes appeared to be different from chronologies derived from the remaining trees.