Investigation of induced resistance against Fusarium circinatum in Pinus patula

Abstract

Pines represent over 50% of the trees planted by forestry companies in South Africa. They are valued not only for their oils and biofuels, but for their solid timber, pulp and paper. Diseases pose a threat to pine trees. In particular the necrotrophic pathogen Fusarium circinatum causes pitch canker disease on Pinus patula. The pathogen causes significant losses to P. patula production in the forestry sector. Due to the economic impact of this problem, means to reduce disease incidence are being investigated, including the prospect of improving resistance in P. patula. One of the means of improving resistance is the enhancement of defences using chemical or biologically derived products to elicit an array of signalling pathways which lead to the expression of defence related genes, a phenomenon known as induced resistance. Induced resistance includes systemic acquired resistance (SAR) and induced systemic resistance (ISR). Each of these responses is associated with specific plant hormones, activation of specific defence genes and is effective against different pathogens. Due to the uniqueness of each pathway the defence proteins can be used as markers to identify the onset of each respective pathway. The aim of this MSc study was to identify and select inducers which effectively trigger induced resistance against F. circinatum in P. patula seedlings and to determine whether the treatments were accompanied with an induction of marker genes associated with induced defence. Chapter 1 is a review of the literature concerning the P. patula - F. circinatum plant pathogen model. This chapter begins with information on the importance of pine for the forestry industry and the losses caused by this fungal pathogen. It further describes the function of induced resistance and its use in agriculture to combat diseases. Finally a few examples of inducers are provided, focusing on their function in induced resistance and their successful application in agriculture.