Impact of elevated temperature on the association between Crotalaria spectabilis and different species of arbuscular mycorrhizal fungi

Details

Supervisors

Declerck, Stephan

Faculty

Faculté des sciences

Degree label

Master [120] en biologie des organismes et écologie, à finalité didactique

Abstract

Impact of elevated temperature on the association between Crotalaria spectabilis and different species of arbuscular mycorrhizal fungi: As predicted by scientific models the world climate is changing and terrestrial temperatures are expected to increase by the end of the century. Arbuscular Mycorrhizal Fungi (AMF) are widespread soil microorganisms forming symbiotic associations with a majority of plant species, increasing their growth and resistance to biotic and abiotic stresses. Understanding the effect of increasing temperatures on these plant symbionts is thus of paramount importance. Some studies have reported the effects of increasing temperatures on plants and AMF. A number of results concerned the root colonization by the fungus or the plant biomass. Concerning AMF sporulation, increasing as well as decreasing numbers of spores have been mentioned. However, no study was conducted under strict in vitro culture conditions, allowing to circumvent any unwanted parameters, and compared different AMF species. Originally this master thesis aimed to study (1) the impact of the temperature on several mycorrhizal parameters and (2) the importance of the fungal intraspecific diversity in the mycorrhizal response to an increased temperature. Because of the COVID and a time restriction, the number of strains of AMF studied has been reduced making the studying of this second aspect difficult. Finally, this thesis has mainly concerned the impact of the temperature on the sporulation of AMF. Two strains belonging to two different species of AMF (Rhizophagus irregularis and Rhizophagus diaphanus) have been inoculated to plants (Crotalaria spectabilis) under in vitro conditions. The plant-AMF associates were grown in growth chambers at two different temperatures and the spores produced were counted at regular intervals. Results of these counts have been analysed with a linear mixed model in R. It can be seen from the best suited model that temperature has a significant effect on the spore production among the fungal species studied for the period and the experimental conditions considered. During the first four weeks the systems placed at 27 degrees Celsius had a higher sporulation that the systems placed at 24 degrees. But after the fourth week, the sporulation of the 24-degrees systems became higher, showing an interaction between the temperature treatment and the time. The temperature impact on the two AMF species was not significantly different. Several ways have been proposed to improve the experiment and the experimental design for experiments similar to this one in the future. The effect of the temperature and that from the access to the water could be better discriminated. An analysis involving "S-shape" curves could also be better than an analysis involving the adjusting of a straight line to the data of each system. Finally, an automatic or semi-automatic counting of the spores should be envisaged seeing the effort required for the counting of one system when the sporulation is abundant. Programs already exist for the measuring of hyphae and roots for example.