Abstract:
Many countries have established commercial plantations of Pinus spp. to accommodate a growing demand for wood and timber products. In the Southern Hemisphere, where Pinus spp. are non-native, establishment of these plantations commenced in the mid-19th century. Several different species were introduced and tested on different sites, and some have more recently been selected for breeding and the establishment of hybrid clones. This has resulted in the considerable movement of seed and other forms of germplasm across different continents and concomitantly microbial pathogens have also been introduced into new environments. Several of these organisms include important pathogens and consequently there has been an emergence of disease outbreaks that, in some cases, have severely impacted the profitability of commercial plantations in the Southern Hemisphere. This dissertation focusses on what is known regarding the pine needle diseases that have been reported affecting non-native Pinus spp. commercially grown in the Southern Hemisphere, especially pertaining to the genera Lecanosticta and Lophodermium. The findings arising from the studies presented in this dissertation illustrate how anthropogenic activities have led to the introduction and distribution of microbial organisms, including pathogens, into non-native Pinus spp. commercially grown in the Southern Hemisphere. They have also highlighted the importance of using DNA sequence data in conjunction with the morphological observations to accurately identify the fungal species, especially for species from these genera. The studies have also identified several new pine hosts for the fungal species studied, especially Pinus spp. native to Mesoamerica. Extreme caution thus should be applied to prevent the accidental introduction of these fungal species together with plant material in the future . This is especially as Mesoamerican Pinus spp. are becoming increasingly important to the commercial forestry industry in the Southern Hemisphere.
