Two new male-sterile mutants on chromosome 9 have recently been identified. Earl Patterson of the University of Illinois found one of these male-steriles and identified it as ms*-6011. He determined that several other unknown male-sterile mutants were allelic to ms*-6011. They were ms*-6018, ms*-6027 and ms*-6031. By using B-A translocations, he found that they mapped to the long arm of chromosome 9. He also determined that they were not allelic to ms2 (see MNL 69:126-128).
MRT made testcrosses between ms*-6031 and the other known male-sterile mutants on chromosome 9 (ms25 and ms45). ms*-6031 also was crossed with ms27, while ms*-6011 was testcrossed to ms24 (both unmapped male-sterile mutants). A minimum of 40 plants was grown from each testcross. Fertile plants were observed in all testcrosses indicating that they were not allelic to any known male-sterile mutants.
MCA found the other male-sterile mutant in 1985 in a row of Country
Gentleman sweetcorn in our Johnston, IA, nursery. He selfed fertile sib
plants and sib pollinated the male-sterile plant that he found. The selfed
ears were grown in 1986 in our Johnston nursery where they segregated for
male sterility, and where crosses to male-sterile plants were made with
B73. In 1993 we re-discovered this male sterile in our inventory, named
it ms*-MS85A and planted it in our summer nursery. We selfed the
F1 B73 crosses and grew the F2 seed in our 1994 Johnston nursery, separating
non-sugary and sugary kernels. Segregations for the original selfed ears
and the B73 crosses are shown below:
| Genotype | Fertiles | Steriles | X2(3:1) |
| Country Gentleman Ear #5 | 18 Fertiles | 4 Steriles | 0.55 |
| Country Gentleman Ear #10 | 9 Fertiles | 1 Sterile | 1.20 |
| B73 Non-sugary F2 | 32 Fertiles | 4 Steriles | 3.70 |
| B73 Sugary F2 | 28 Fertiles | 4 Steriles | 2.67 |
In our 1995 Hawaii winter nursery, leaf samples were taken for chromosome mapping. TWF performed bulk mapping as described in MNL 72:37 except that 20 male-fertile and 17 male-sterile plants were used in the creation of the DNA pools. Markers bnl5.09 and bnl14.28 on chromosome 9L were both polymorphic between the two pools. Hybridization of these probes to DNA blots of the male-sterile individuals revealed four and one recombinant individuals, respectively, indicating that ms*-MS85A is linked to both RFLP markers on chromosome 9L.
We made reciprocal test-crosses (when possible) of ms*-MS85A
to the other known male-sterile mutants on chromosome 9 (ms2, ms25,
ms45), as well as to the unmapped male-sterile mutants ms24
and ms27. A minimum of 40 plants was grown of each test-cross. All
of the resultant progeny showed fertile plants, indicating that ms*-MS85A
was not allelic to any of the known male-sterile mutants. Because Earl�s
Group 2(9L) male steriles (see MNL 69:126-128) also mapped to chromosome
9, reciprocal testcrosses were made. In this case we used ms*-6031
to cross with ms*-MS85A. A minimum of 40 progeny from both crosses
were grown producing all fertile plants, indicating that the two male-sterile
mutants were not allelic to one another. Because neither of these male-steriles
are allelic to any known male steriles, nor to each other, we believe they
are new genetic male-sterile mutants. We are designating ms*-6011
as the reference allele for ms35, a new male-sterile mutant. Its
alleles described here will be known as ms35-6018, ms35-6027
and ms35-6031. ms*-MS85A will be designated as the reference
allele for a new male-sterile mutant identified as ms36.
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