Two additive, independent genes for mycelial growth versus sporidial growth of haploid cultures of Ustilago hordei

Abstract

Three distinct haploid colony phenotypes, (1) sporidial, containing no hyphae and smooth-surfaced; (2) intermediate, containing some hyphae and usually smooth-surfaced; and (3) mycelial, containing more hyphae, rough-surfaced, and rapidly spreading, were recognized in F1, haploid lines of Ustilago hordei (Pers.) Lagerh. derived from a cross of two intermediate lines, E3a and 14A. Crosses among all phenotypes and analysis of unordered progeny tetrads and random sporidial isolations revealed that two loci, one from each parental line, govern this trait. The loci are independent and their effects are additive. One locus, in line E3a, is linked to the mating-type locus.Tetrad sets from Tapke's 13 races were examined and in no case was segregation for this trait seen.