A case of aberrant transmission of genetic factors on the short arm of chromosome 9 in maize

Abstract

A locus on the short arm of chromosome 9 completely prevents the transmission of the male gametes carrying it. The female gametes bearing it also have a slightly, but significantly, lower rate of transmission. The locus was mapped at 1.13 units distal to I. The four markers linked to this locus show a polarity of transmission, the transmission of I, Sh, Bz and Wx being 1.13, 2.26, 4.49 and 27.18% respectively. For I it was verified that the transmitted gametes were due to crossing over between I and the 'distorting' locus and the same can be inferred for the other loci from the polarity effect. The basis of the aberrant transmission was considered to be either a mutation of a gametophytic factor or, more likely, a cryptic deletion. Although no aberration was detected cytologically and the stainability of pollen was normal, the transmission data are more compatible with the deletion model since the slightly lower transmission through the female would not be expected from a gametophyte mutation.