JOHNSTON, IOWA
Pioneer Hi-Bred Int., Inc.
New male-sterile mutant allele of Ms22 --Trimnell, MR, Fox, TW, Albertsen, MC A new male-sterile allele of Ms22 has been identified. The new allele was among male-sterile mutants received from the late Dr. Earl Patterson. Earl had designated it as ms*-6036 (see MNL 69:126-128).

We planted an F2 segregating line of ms*-6036 in our 1998 Hawaii nursery to determine the chromosome arm map location of the mutant as part of our standard procedure in working with previously unlocated male steriles. We first determine the chromosome arm location, then we conduct the appropriate allelism crosses. Leaf punches were taken from 24 male-sterile plants and from 24 male-fertile plants for DNA isolation. SSR markers were used to genotype these samples. Out of 72 randomly dispersed SSR markers, only one, phi034, showed linkage to the male sterility trait. This marker maps to bin 7.02 on chromosome 7, and segregates with ms*-6036 as follows:
 
  Homozygous (A) Heterozygous (AC) Homozygous (C) Failed Rxns
Fertile
9
10
2
3
Sterile
0
6
16
2

Although only one marker showed linkage, we proceeded to test-cross ms*-6036 with the recessive male-sterile mutants that are located on chromosome 7 (ms7, ms22, ms34), as well as with an unmapped recessive male-sterile mutant (ms27). The resultant progeny were grown in our 2000 Johnston, Iowa, nursery. At least 40 plants were observed for each of the test-crosses. The reciprocal test-crosses with ms27, ms7 and ms34 produced all fertile progeny, indicating ms*-6036 was not allelic to them. The reciprocal test-crosses of ms*-6036 with ms22 gave the following results, indicating allelism:
 
Female Male
Progeny
X2
ms*-6036 Heterozygote ms22 Het
34 Fertiles
8 Steriles
0.79 (3:1)
ms22 Homozygote ms*-6036 Het
26 Fertiles
22 Steriles
0.33 (1:1)

Our new designation for this Ms22 male-sterile allele is ms22-6036.
 
 


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