New chromosome 9L male-sterile mutants ms35 and ms36
--Trimnell, MR, Patterson, E, Fox, TW, Albertsen, MC

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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