BGN 2: Chromosome location of locus mlo conditioning resistance to powdery mildew BARLEY GENETICS NEWSLETTER, VOL. 2, II. RESEARCH NOTES
Jørgensen, pp. 31-32

II.7. Chromosome location of locus mlo conditioning resistance to powdery mildew.

J. Helms Jørgensen. Danish Atomic Energy Commission. Research Establishment Risø, DK-4000 Roskilde, Denmark.

An induced mutant gene in a locus designated mlo conditioning resistance to the powdery mildew fungus (Erysiphe graminis f. sp. hordei) is inherited independently of the spontaneous mildew resistance genes Mlo, MlpMlr12,  and Mls on chromosome 5 and Mlg on chromosome 4 (Jørgensen 1971). In order to locate mlo to one barley chromosome the resistant mutant R 5678 (CI 15219) was crossed to a trisomic set of barley lines. Trisomic F1 hybrids were selfed and the seven F2 seedling populations were scored for reactions to culture 59.11 of E. graminis hordei with the following results:

The F2 population from chromosome 4 trisomics segregating 8.5 per cent resistant seedlings indicate that mlo is located on chromosome 4, probably on the short arm because mlo is independent of mlg on the long arm. Locus mlo is being mapped relative to known marker genes on chromosome 4.


Jørgensen, J. Helms, 1971. In: Mutation Breeding for Disease Resistance, Intern. Atomic Energy Agency, Vienna, 117-124.

BGN 2 toc
BGN Main Index