We planted an F2 segregating line of ms*-6049 in our 1999 Johnston, IA, nursery to determine the chromosome arm map location of the mutant as part of our standard procedure in working with unmapped male-sterile mutants. We first determine the chromosome arm location. Then we conduct the appropriate allele test-crosses. Leaf punches were taken from 24 male-sterile plants and from 24 male-fertile plants for DNA isolation. 96 SSR markers were used to genotype these samples. The ms*-6049 mutant maps to the long arm of chromosome 9, with two SSR markers being linked. Only two recombinant alleles from 19 mutant plants (38 alleles total) were found with either bngl1012 or bngl1159, indicating fairly tight linkage with the mutation.
After receiving the mapping data, we test-crossed ms*-6049 with
the recessive male-sterile mutants found on chromosome 9 (ms2, ms25,
ms36, ms45), as well as the unmapped male-sterile mutants
(ms27, ms31) and those with questionable mapping data (ms23,
ms35). The resultant progeny were grown in our 2001 Johnston nursery. At
least 40 plants were observed for each test-cross. All test-cross progeny
were found to be fertile, indicating that ms*-6049 was not allelic
to any of the tested mutants. Our new designation for male-sterile mutant
ms*-6049 is ms48.
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