Fertility compensation of cornerstone male sterility of wheat by rye.

The genome of rye is known to compensate for the lost male-fertility gene(s) of wheat chromosome arm 4Aalpha in the Cornerstone male-sterility mutant. A search for the rye chromosome(s) involved in this compensation showed that chromosomes 2R and 4R are responsible. Only the short arms of these two chromosomes are the operative ones. Chromosome arm 4RS compensates in an erratic way, whereas 2RS compensates in a full and consistent way. The entire chromosome 2R compensates less well than the 2RS telocentric which reflects an antifertility factor(s) on 2RL. This may be a specific expression of the 2R genes for poor vigor which are located on only the long arm. 2RS will be a valuable piece of chromatin for the XYZ system of producing hybrid wheat.