PARENT SESSION
Posters P6D Crop photosynthesis, agricultural biotechnology. Abstracts (742-753)

Septoria leaf blotch: Effects on Photosystem II and on leaf pigment content. Fabienne Crumière^*,1, Reto Strasser², Daniel Reisen¹, Lucien Hoffmann¹, Jean-François Hausman¹, ¹ CRP-Gabriel Lippmann, CREBS Research Unit, Luxembourg, Luxembourg² Bioenergetics laboratory, Jussy-Geneva, Switzerland

ABSTRACT- Septoria tritici (anamorph of Mycosphaerella graminicola) probably causes the most serious foliar disease of winter wheat. The top three leaves contribute mainly to grain yield, so they should be kept free from infections. A simulation model has been developed to define, in real time, the risk of progression of Septoria tritici on the upper leaves during stem elongation and to guide the farmers in fungicide application at the right time in order to protect these leaves. For this study, we worked on Achat cultivar, a winter wheat. Photosynthetic parameters and pigment content were measured for three specific conditions defined as followed: control leaves (leaves apparently healthy, collected from the control plot not treated by fungicides), treated leaves (leaves apparently healthy, selected from the plot treated by fungicides) and diseased leaves (leaves with necrotic surfaces due to Septoria tritici infection, collected from the control plot not treated by fungicides). Chlorophyll a fluorescence is a useful and non-invasive tool to detect changes of structure and function of the photosynthetic apparatus. The polyphasic chlorophyll fluorescence transient, obtained from wheat leaves after excitation with red light, was measured with a portable fluorimeter with high time resolution. The subsequent data were analysed using the JIP-test which produces various biophysical parameters indicating photosystem II properties. Chlorophyll measurements showed a significant difference between control and diseased leaves, with a performance index decrease of 67% in the latter. No real difference was observed between control and treated leaves. The incidence of Septoria tritici on photosystem II of wheat leaves will be discussed.

KEY WORDS: JIP-test, winter wheat, chlorophyll a fluorescence, Septoria tritici