Linkage studies involving two chromosomal male-sterility mutants in hexaploid wheat.

The factors for Cornerstone and Probus male sterility are allelic on chromosome arm 4Aalpha. They map independently of the centromere, but show linkage with a rye segment located 1 crossover unit from the centromere on the beta arm. The alien segment causes asynapsis and some precocious terminalization of chiasmata when in repulsion with the mutants. The mutants, presumed to be terminal deletions, cause some desynapsis, but not asynapsis.