New chromosome 10S male-sterile mutant: ms29
--Trimnell, MR, Fox, TW, Albertsen, MC

In 1984 a male-sterile mutant was identified in elite proprietary breeding material by Steve Noble in Johnston, Iowa. The male-sterile mutant was out-crossed and selfed. The F2 seed segregated as follows, indicative of a single recessive gene:
 
Ear Number Fertiles Steriles X2
1 4 7 8.76**
2 11 3 0.10
3 10 4 0.10
4 11 6 0.96
5 10 4 0.10
6 12 4 --
      **significant at 0.01 level 

This male-sterile mutant was designated as ms*-JH84A. We crossed ms*-JH84A with known genetic male-steriles in 1989 through 1996 to determine allelism. Known male-steriles used in test-crosses were ms1, ms3, ms5, ms7, ms8, ms9, ms10, ms11, ms12, ms13, ms14, ms17, ms20, ms22, ms23, ms24, ms25, ms26 and ms27. Progenies of these test-crosses were grown from 1990 through 1997. ms*-JH84A was not found to be allelic to any of them (at least 20 plants were observed for each test-cross). In 1995, progeny from a segregating F2 ear was grown for bulk mapping the gene. Barb Hobart of our Genetic Markers Lab combined equal amounts of DNA from 26 male-fertile plants and 17 male-sterile plants grown from the F2 ear. DNA blots were constructed using bulked DNA digested with four different restriction enzymes (BamHI, EcoRI, HindIII, EcoRV). These blots were sequentially hybridized with approximately 50 RFLP markers that were evenly spaced throughout the genome. Since ms*-JH84A is a recessive mutation, polymorphisms were scored based on the absence of the wildtype band in the male sterile bulk lane. The marker umc130 on the short arm of chromosome 10 gave a clear polymorphism. Linkage was confirmed by hybridizing DNA from the individuals with umc130. This marker segregated as either homozygous A allele or as heterozygotes in the male-fertile individuals, whereas all of the male-sterile individuals were homozygous for the B allele.

There are two male-sterile mutations, ms10 and ms11, located on the long arm of chromosome 10. We re-crossed ms*-JH84A with both ms10 and ms11 and, in each case, verified it was not allelic to either mutant. Because ms*-JH84A is not allelic to ms10 or ms11, nor allelic to any of the unmapped known male-sterile genes, it is a new genetic male-sterile mutant. We are designating it as ms29.


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