Maturation of Mycosphaerella graminicola pseudothecia on wheat plants inoculated for heritability analysis of QoI resistance

For better understand of the recent rapid spread of QoI resistane in Mycosphaerella graminicola populations, the behaviour of this resistance during the sexual cycle was invetigated. The mating type, the mitochondrial inherited QoI sensitivity and the sensitivity to an inhibitor of the nuclear inherited alternative oxidase were characterised for single conidia of M. graminicola strains isolated in Belgium. Wheat seedlings were inoculated with various combinations of strains before incubation outside in a wheat field as well as away from any wheat field. Analyses of single conidia produced by pycnidia from mixed inoculations suggest the occurrence of an early exchange of mitochondria among some strains. Monitoring of pseudothecium development on inoculated and spontaneous infected plants led to the first detection in Belgium of fertile M. graminicola pseudothecia and to the isolation of single ascospore strains. Besides the inoculated M. graminicola genotypes, or possible recombinants spontaneous contaminations were frequent and interfered in the QoI resistance heritability study.