Fine structure and instability of the Ml-a locus in barley
Wise, R.P.; Ellingboe, A.H.
Genetics 111(1): 113-130
1985
ISSN/ISBN: 0016-6731 PMID: 4029608 Document Number: 265777
There are many naturally occurring variants at the Ml-a locus in barley that confer resistance to the powdery mildew fungus Erysiphe graminis f. sp. hordei. Since the Ml-a locus is bracketed by Hor-1 and Hor-2, genes that encode storage proteins in the endosperm, the Ml-a locus is amenable to fine structure analysis. Rare susceptible recombinants, as judged by exchange of flanking markers, were recovered in F3 families from the Ml-a10 .times. Ml-0a1, Ml-a1 .times. Ml-a15 and the Ml-a6 .times. Ml-a13 crosses. Some susceptible recombinants where recovered from the Ml-ab .times. Ml-a13 cross that did not fit the expected F3 family segregation ratios. The Ml-a6/Ml-a13 recombinants often reverted to resistance in subsequent generations. No recombinants were recovered in the reciprocal cross, Ml-a13 .times. Ml-a6. The possibility of a transposable element and a possible linear order of 6 alleles at the Ml-a locus is discussed.