New chromosome 2L male-sterile mutants ms30 and ms31
--Trimnell, MR, Fox, TW, Albertsen, MC

Two new male-sterile mutants on chromosome 2 have recently been identified. One was observed in 1987 in Willmar, MN by Bob Rosenbrook. It was segregating in an elite proprietary breeding line. Remnant seed from the F3 line was sent to us and planted in 1988. We crossed male-sterile plants from this F3 as female with public inbreds A632 and B73. F1 plants were selfed. F2 segregations were as follows:
 
Genotype Fertiles Steriles X2 (3:1)
A632 Ear #1 6 Fertiles 8 Steriles 7.71**
A632 Ear #2 7 Fertiles 4 Steriles 0.76
B73 Ear #1 11 Fertiles 6 Steriles 0.96
B73 Ear #2 7 Fertiles 4 Steriles 0.76
      **significant at 0.01 level

We designated this male sterile as ms*-WL87A and maintained it in both A632 and B73. We crossed ms*-WL87A in 1989 through 1996 with the known genetic male steriles. Known male steriles used were ms1, ms2, ms5, ms7, ms8, ms10, ms11, ms12, ms13, ms14, ms17, ms20, ms22, ms23, ms24, ms25, ms26 and ms27. Progenies of the test-crosses were grown from 1990 through 1997 (at least 20 plants per test-cross were observed). ms*-WL87A was not allelic with any of them. In 1995 a segregating F2 ear was grown for bulk mapping. Barb Hobart conducted the bulk mapping as previously described (see ms29 article, this issue), except that 20 plants from each fertility class were used in the creation of the pools. Although individual DNA blots have not been run on this family, the RFLP marker umc4 on chromosome 2L was clearly polymorphic between the two bulks, supporting the hypothesis that ms*-WL87A is located on chromosome 2L.

The other male-sterile mutant was observed in 1989. It was segregating in an F2 from an elite breeding cross. We designated this male sterile as ms*-CG89D. Male-sterile plants were out-crossed with A632 and then selfed. The resultant F2 seed segregated as follows:
 
      X2 (3:1)
Ear #1 20 Fertiles 1 Sterile 4.59*
Ear #2 21 Fertiles  2 Steriles 3.26
      *significant at 0.05 level

As these results were inconclusive for a single gene, F2 male-sterile plants were backcrossed to A632 and selfed a second time. This resulted in the following segregation, more suggestive of a single recessive gene:
 
      X2 (3:1)
Ear #1 15 Fertiles 1 Sterile 3.00
Ear #2 10 Fertiles 5 Steriles 0.56

The F1 cross with A632 was used to make test-crosses in 1990 with known genetic male steriles. Additional test-crosses were made from 1991 through 1996. Known male-sterile mutants used were ms1, ms5, ms7, ms8, ms9, ms10, ms11, ms12, ms13, ms14, ms17, ms20, ms22, ms23, ms24, ms25, ms26 and ms27. Progenies of the test-crosses were grown from 1991 through 1997 (at least 20 plants per test-cross were observed). ms*-CG89D was not allelic with any of them. In 1993 a segregating F2 ear was grown for bulk mapping. For this mutant, Robin Tenborg, also of the Genetic Markers Lab conducted the bulk mapping. Twenty individuals from each fertility class were used in the bulked pools. The RFLP marker umc36, on chromosome 2L, gave a good polymorphism between the two bulked classes. DNA blots of the individual plants showed 100% linkage of the male sterile lanes with umc36. The wildtype individuals segregated normally.

Because ms*-WL87A and ms*-CG89D were both mapped to the long arm of chromosome 2, crosses were made between the two male-sterile mutants. The resultant crosses were grown, and no male-steriles were found (approximately 80 plants were observed). Because no male steriles have been described on 2L, and because the currently described mutants are not allelic to one another, they are new genetic male sterile mutants. We are designating ms*-WL87A as ms30 and ms*-CG89D as ms31.


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