| The majority of agricultural important plant species form naturally a symbiosis with arbuscular mycorrhizal (AM) fungi. These fungi offer several benefits to the host plant including faster growth, improved nutrition, higher drought resistance, and in certain cases protection against root pathogens. Both these benefits, and the increased concern for environmental quality, supports the interest of these microorganisms for management practices in agricultural and horticultural systems.
However, the effects on AM fungi of cultural practices, such as fungicide use for the control of pests and fungal disease agents, are not often measured. Repeated doses or soil accumulation of these fungicides could have detrimental effects on plant growth by limiting the functioning of AM symbiosis.
Up to date, very little information is available on the effects of fungicides on the AM fungi, with regard to their lipid metabolism. In order to assess the impact of these fungicides on AM fungi, the proposal will focus on the sterol biosynthesis inhibitors (SBI) which are the major class used as agricultural fungicides.
Three complementary approaches will be considered : (1) the study of the effects of SBI fungicides on the AM symbiosis, (2) the changes in sterol composition of AM fungi under the impact of fungicides in order to get information on the mechanism of fungicides action and on the fungal sterol metabolism and (3) the effects of SBI on sterol biosynthesis gene regulation.
The major results expected are (1) a better knowledge of the fungicides effects on AM fungi and symbiosis within the framework of supervised agriculture in order to minimize or adapt the use of fungicides to the establishment of a functional symbiosis and (2) a better basic knowledge of sterol metabolism of these fungi. |