II. 13. A balanced male sterile-chloroplast mutant scheme for hybrid barley.
C.A. Foster, Welsh Plant Breeding Station, Aberystwyth, Wales, UK.
The existence of semi-dominant or incompletely dominant chloroplast mutations, in which the heterozygotes are viable but distinguishable from the homozygous normals, while the homozygous recessives are lethal, provides the opportunity to develop a simple diploid system for producing "all male sterile" progeny for use in F1 hybrid barley production.
With a very close linkage between a suitable semi-dominant chloroplast mutant and a male sterile locus the selfed progeny of a double heterozygote Msa//msA, which would be viridis and viable under optimal conditions, would consist of 25% normal green male steriles (msA//msA), 50% viridis fertiles (Msa//msA) and 25% albino plants (Msa//Msa). Under competitive conditions in the field the viridis plants would probably not survive, leaving the normal green plants to serve as the female parent in F1 hybrid seed production, with no or minimal roguing being required. The viridis plants would be separately multiplied under optimal conditions of high light and/or high temperature according to their requirements.
At least 27 male sterile loci are known, while the identity of many more male sterile stocks remain to be determined. At least two suitable semi-dominant chloroplast mutants are known (see note by author in this issue). Crosses between one of these (Cb 3369) and available male sterile stocks are being made in order to establish a balanced male sterile-chloroplast mutant genotype.