Fine structure of genes controlling pathogenicity in flax rust, melampsora luni

Abstract

The fine-structure of four genes, A-F, A-P1, A-P2 and A-P3 in the flax rust organism, Melarnpsora lini, that control pathogenicity on the host, Linum usitatissimum, has been investigated by using a mass-screening procedure to search for rare recombinant progeny. Three presumptive recombinant individuals were recovered from amongst 3160 dikaryotic test-cross progeny and seven from a second test in which haploid basidiospores were screened for recombinants. From the pathogenicity phenotypes of the presumptive recombinants, and their frequency of occurrence, it is concluded that genes A-P, A-P1, A-P2 and A-P3 are sufficiently closely linked to belong to the same cistron. However, the possibility that they belong to separate, closely-linked cistrons can not be excluded: if they do belong to separate cistrons, then the data suggest that these are contiguous. A tentative gene order A-P A-P2 A-P1 A-P3 is proposed. © 1981 The Genetical Society of Great Britain.