Three point linkage data for wx1 inr2 v30

--Stinard, PS

Dominant mutant alleles at the inr2 locus suppress aleurone color in crosses to specific r1 haplotypes (Stinard and Sachs, J Hered 93:421–428, 2002). Previous work (Stinard, MNL 77:76–66, 2003) places inr2 on the long arm of chromosome 9, approximately 23 cM from wx1. In order to refine this placement, we conducted a three point linkage test of wx1, inr2, and v30, the latter locus being on the long arm of chromosome 9 in the vicinity of where inr2 would be expected to map. The linkage testcross and results are indicated in Table 1. All lines are homozygous for the suppressible haplotype R1-Randolph to allow scoring for inr2. Kernels were scored for wx1 and inr2 on the test cross ears at maturity, and these kernels were subsequently planted in a cold sand bench and the resulting seedlings were scored for v30.

This linkage test establishes the global gene order as wx1 inr2 v30. The wx1-inr2 distance (22.3 ± 0.8 cM) agrees closely with those obtained previously (22.6 ± 0.9 cM and 22.9 ± 1.2 cM). The wx1-v30 distance (32.0 ± 0.9 cM) agrees with that indicated on the 1993 genetic map of chromosome 9 (31 cM; Neuffer et al., Mutants of Maize, Cold Spring Harbor Laboratory Press, 1997). inr2 maps about 9.7 cM proximally to v30, in the vicinity of bk2.


Table 1. Three point linkage data for wx1, inr2, and v30.

Testcross: [Wx1 Inr2-JD V30 R1-Randolph × wx1 inr2 v30 R1-Randolph] × wx1 inr2 v30 R1-Randolph.

Region Phenotype No. Totals
0 Wx Inr V 897  
  wx inr v 938 1835
1 Wx inr v 261  
  wx Inr V 282 543
2 Wx Inr v 106  
  wx inr V 106 212
1 + 2 Wx inr V 23  
  wx Inr v 21 44

Map distance wx1inr2 = 22.3 ± 0.8 cM
Map distance inr2v30 = 9.7 ± 0.6 cM
Map distance wx1v30 = 32.0 ± 0.9 cM