To reduce the number of test-crosses required to determine allelism, we planted an F2 segregating family of ms*-6028 in our 1998 Johnston nursery for chromosome arm mapping. Leaf punches were taken from 23 male-sterile plants and 24 male-fertile plants for DNA isolation. Approximately 60 SSR markers, evenly dispersed throughout the genome, were used to genotype these samples. Linkage was found between the SSR marker phi093 (chromosome 4, Bin 8) and the male-sterile phenotype.
After receiving the mapping data, we
test-crossed ms*-6028 with the recessive male-sterile alleles that
are located on chromosome 4 (ms30), as well as the unmapped recessive
male-sterile alleles (ms24, ms27). The resultant progeny
were grown in our 1999 Johnston nursery. At least 40 plants were observed
for each of the test-crosses. The test-crosses with the unmapped male-sterile
mutants were all fertile, indicating ms*-6028 was not allelic to
either mutant. The reciprocal test-crosses of ms*-6028 with ms30
gave the following results, indicating allelism:
Female (homozygous) | Male (heterozygous) |
|
X2(1:1) | |
ms*-6028 | ms30 | 10 Fertiles | 16 Steriles | 1.38 |
ms30 | ms*-6028 | 19 Fertiles | 22 Steriles | 0.22 |
Our new designation for this Ms30
allele is ms30-6028.
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