Studies of genes controlling specific host-parasite interactions in flax and its rust

Abstract

A method used to analyse Flor's M group of genes controlling specific resistance of flax to its rust is described. Using this method, three of seven genes reported so far have been brought together in pairs in coupling. The specific effects of each pair of genes in coupling is a simple sum of each individual gene and identical to the corresponding pair in repulsion, suggesting they are not functionlly allelic. Segregational data show that four of these M genes represent closely linked sites separable by recombination and a possible linear order is suggested. Further analysis awaits the availability of appropriate strains of rust to discriminate M2, M5 and M6 individually and to further distinguish between M' and M4.

Meiosis-Driven Genome Variation in Plants

“…Over 30 rust resistance genes, designated K, L, M, N, and P, have been identified in flax (Linum usitatissimum). Extensive analysis of the L and M loci suggests that the L locus contains a single gene with multiple alleles and the M locus may contain about 15 related genes [61,62]. Only one gene was found to confer resistance specificity at the M locus.…”

Inactivation of the flax rust resistance gene M associated with loss of a repeated unit within the leucine-rich repeat coding region.

“…Ellis, unpublished results). Some of these specificities (M7, M3, and M4) have been recombined with the M resistance specificity and brought together on the same chromosome (Flor, 1965;Shepherd and Mayo, 1972;Mayo and Shepherd, 1980). In these cases, the recombinant M locus contains at least two genes that provide rust resistance of different specificity.…”

“…Genetic analyses indicate that genes in the L group are most likely allelic to each other (alternative forms of a single gene); no recombinants expressing both parenta1 specificities have been detected between many pairs of L specificities in large numbers of testcross progeny (Flor, 1965;Shepherd and Mayo, 1972;lslam et al, 1989). In contrast, similar studies involving pairs of M specificities have recovered recombinants expressing both parenta1 specificities, which indicates that at least some members of the M group are separate but closely linked genes (Flor, 1965;Mayo and Shepherd, 1980).…”

Fine structure of genes controlling pathogenicity in flax rust, Melampsora lini

“…The results of these studies have been interpreted as indicating that the genes in the L group belong to the same cistron, that is, they are functional alleles, and that the genes in the M and N groups most likely belong to separate, closely-linked cistrons. With the M genes these studies have also provided evidence as to the linear order of some of these genes (Mayo and Shepherd, 1980).…”

“…These groups., designated K, L, M, N, and P, contain 1, 13, 7, 3 and 5 genes respectively. The structure of the genes within these groups has been investigated by screening for rare recombinants amongst large numbers (often thousands) of progeny from a plant heterozygous for two resistance genes from the same group (Shepherd, 1963;Flor, 1965b;Shepherd and Mayo, 1972;Mayo and Shepherd, 1980). The results of these studies have been interpreted as indicating that the genes in the L group belong to the same cistron, that is, they are functional alleles, and that the genes in the M and N groups most likely belong to separate, closely-linked cistrons.…”