DIFFERENTIAL SENSITIVITY OF WHEAT EMBRYOS AGAINST EXTRACTS CONTAINING TOXINS OF SEPTORIA-NODORUM - FIRST STEPS TOWARDS IN-VITRO SELECTION

As a first step towards the development of an in vitro-selection system for septoria nodorum blotch resistance, wheat embryo culture on media containing extracts from Septoria nodorum was established. Extracts prepared from inoculated wheat grains had a toxic activity. Control extracts from uninoculated grains showed at least a 10-fold lower toxic activity. Two wheat breeding lines susceptible to Septoria nodarum showed reduced growth in the presence of the fungal extract when compared to a breeding line known to have good resistance in the field. A test with seven additional wheat lines showed a good agreement between field resistance of the ear and embryo resistance. Mellein is one of the toxins produced by Septoria nodorum and was used in pure form for in vitro-selection. It showed toxic effects at 50 mu g/ml, a concentration which is about 200-fold higher than the mellein concentration in the diluted extract with embryotoxic activity. This indicates the importance of additional toxic compounds in the crude extract. Mellein acted non-selectively on embryos of the different cultivars.