BROOKINGS, SOUTH DAKOTA

South Dakota State University

Mapping of ragged (rg*) mutation using classical and molecular markers

Whalen, RH; Brozik, M; Auger, D

A recessive mutation resulting in abnormal leaves and shorter plants was found in the inbred W22. This apparently spontaneous mutation was informally designated “ragged” (rg*) in reference to its cut or torn leaves (Fig. 1). It was found to be due to a single recessive gene, and using B-A translocations, was found to be on the long arm of chromosome 5. We mapped it more precisely in a three-point linkage test with red aleurone (pr) and the SSR molecular marker umc1221. The reference allele for umc1221 has seven tandem copies of CT. Determination of polymorphisms was accomplished through electrophoretic separation in a 3.5 % agarose TAE gel of polymerase chain reaction (PCR) products that included the SSR. The mapping sample was produced by crossing an F1 heterozygous for all three loci by a homozygous testcross parent (Fig. 2). The data from the mapping sample are presented in Table 1.

The rg* locus is located on the long arm of chromosome 5, 6.8 ± 1.4 cM from pr1, which is 7.9 ± 1.4 cM from umc1221. The map is shown in Fig. 3. This places the new locus distal to pr1.

Table and figures

Table 1. Recombination data

		Family 1	Family 2	Total
Parentals	umc1221-f Pr Rg umc1221-s pr rg	70 77	80 88	157 158	315
SCOs Region 1	umc1221-f pr rg umc1221-s Pr Rg	7 3	7 8	14 11	25
SCOs Region 2	umc1221-f Pr rg umc1221-s pr Rg	5 8	2 6	7 14	21
DCOs	umc1221-f pr Rg umc1221-s Pr rg	3 0	0 1	3 1	4
Totals		173	192	365

Figure 1. Leaf of rg*/rg* plant.

Figure 2. Mapping scheme. 1221s refers to the slower band of umc1221; 1221f refers to the faster band of umc1221. Pr refers to the wild-type allele of pr1; pr refers to the red allele. Rg refers to the wild-type allele of the rg* locus; rg refers to the mutant allele.

Figure 3. Map of new locus relative to pr1 and umc1221.