In vitro screening for resistance against Septoria nodorum blotch in wheat

This study was carried out to develop an in vitro test for the identificati on of genotypes resistant to Septoria nodorum blotch. The basis for this pr oject was a previous study in which a crude extract of S. nodorum was used as a selective agent (Keller et al. 1994). It was possible to distinguish r esistant and susceptible cultivars in an in vitro test with zygotic embryos . In our project we wanted to test whether this in vitro test can also be u sed to detect resistant and susceptible genotypes in early segregating popu lations. Specific crosses between eight winter wheat lines showing contrast ing resistance reaction for S. nodorum blotch on leaves and ears were made. The resistance level of both leaf and ear was evaluated after artificial i noculation in the field for the parental lines, the F-1 progenies, as well as for segregating F-3 and F-4 populations. In addition, this plant materia l was tested in vitro using methods similar to those described by Keller et al. (1994), i.e. culturing immature zygotic embryos and mature seeds on se lective media. A good agreement between in vitro screening and field resist ance on the ear was found for the parental lines, the F-3 and F-4 generatio n but not for the F-3 generations. This leads to the conclusion that the in vitro screening might be integrated into wheat breeding programs. Populati ons showing a high susceptibility to the pathogen metabolites in vitro coul d be discarded. Another promising implementation for wheat breeding would b e the screening of advanced breeding material or candidate partners in a cr ossing program for resistance on the ear. However, the in vitro screening i s not precise enough to select single plants in early segregating populatio ns.