Newly activated germinal Uq elements in maize are clustered on one linkage group independently of the standard Uq element

Summary Allelism tests between the standard Uq element (Uq1) and five newly activated germinal Uq elements (Uq2, Uq3, UQ4, Uq5, and Uq6) demonstrate that these new Uq elements are independent of Uq1. Gametes that either contain one Uq or various combinations of two different and phenotypically distinguishable Uq elements, have been constructed either with or without the a-ruq reporter allele. Genetic analyses of the progenies of the gametes (using the standard a-ruq tested line as the other parent) have indicated that (i) each Uq element, when present alone, has the capacity to express full activity except when a secondary transposition or loss of activity has occurred; (ii) all five new Uq elements are independent of Uq1 with respect to transposition activity; and (iii) these newly originated Uqs are clustered on one linkage group. Uq2 is allelic to Uq4, and Uq3 is allelic to Uq5, whereas Uq6 is linked to both allelic pairs. A putative linkage map of these Uq elements is presented. In reciprocal crosses there is a striking difference in phenotypic segregation of Uq; when transmitted via the male parent Uq loses full expression capacity.