Quarantine is important in restricting the spread of exotic seed-borne tree pathogens in the southern hemisphere
Burgess, T. and Wingfield, M.J. (2002) Quarantine is important in restricting the spread of exotic seed-borne tree pathogens in the southern hemisphere. International Forestry Review, 4 (1). pp. 56-65.
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The lack or destruction of indigenous forests in the southern hemisphere has in some cases led to extensive afforestation with exotic softwoods that subsequently developed into large successful forestry industries. Pinus radiana is the predominant softwood species in the southern hemisphere, with over 3 million ha planted. In its natural environment on the West coast of the United States, P. radiata has been decimated by an epidemic outbreak of pitch canker caused by Fusarium circinatum. The potential devastation of softwood industries in the southern hemisphere, as a consequence of introducing this pathogen, has resulted in strict quarantine regulations. However, this may be too little, too late. F. circinatum is already present in South Africa and it appears that only the lack of an insect vector that has prevented its movement from seedlings to mature trees in plantations. This review considers the risk of introducing new pathogens into the southern hemisphere softwood plantations. The pine pathogen Sphaeropsis sapinea is used as a model to assess future risks, particularly of introducing seed-borne pathogens. The genotypic diversity observed in the pine endophyte S. sapinea, is consistent with historical records of the frequency and quantity of seed and germplasm importation to and within the southern hemisphere. The diversity in South Africa is high, moderate in New Zealand and low in Australia. Many of the genotypes observed were probably introduced before the advent of quarantine. However, new introduced genotypes may be more pathogenic than existing genotypes, potentially leading to more severe disease outbreaks. In pathogens capable of sexual reproduction such as F. circinatum, newly introduced genotypes crossing with existing genotypes would allow for more gene diversity and a greater risk of the pathogen overcoming the trees' resistance. Thus, quarantine is now more important than ever, as limiting the genetic diversity of an exisiting introduced pathogen can be as important as excluding new pathogens.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Biological Sciences and Biotechnology|
|Publisher:||Commonwealth Forestry Association|
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