We report 2-point linkage data for brn1 to ra2 (Table 1), g2 to brn1 (Table 2), and brn1 to d1 (Table 3). Linkage tests were set up as modified backcrosses. Tassels were scored for ra2 just prior to bagging. The trait brn1 was scored on the ears of selfed plants. The traits g2 and d1 were scored in sandbench seedling tests of selfed ears. The trait g2 could not be reliably scored- in seedling tests of selfed ears where it was in coupling with brn1. The pale green seedling phenotype of brn1 brn1 plants masked the expression of g2, and crossovers placing golden plants into the yellow class of kernels from these ears were too infrequent to allow reliable classification. Therefore, data from the selfed ears segregating brn1 were not used in calculating the percent recombination for g2 to brn1.

If one combines our 1986 linkage data (MNL 61:6) with this year's data (Table 3), one obtains a map distance of 19.69 ± 1.56 cM for brn1 to d1. This value places brn1 about 2 cM distal to cr1 on chromosome 3. If one combines our g2 - brn1 map distance (15.82 ± 1.99 centimorgans) with our brn1 - d1 distance, one obtains an approximate g2 - d1 distance of 35.5 cM. This would place g2 3.5 cM further out on 3S than indicated on the 1987 linkage map. Good 3-point linkage data will be required to confirm this.

Table 1. Linkage data for brn1 to ra2.

Table 2. Linkage data for g2 to brn1.

• The values for the brn1 classes were not used in calculating the % recombination because classification for g2 in seedlings grown from brn1 kernels is uncertain. Had these values been included, the % recombination for g2-brn1 would be 14.12 ± 1.34.

Philip S. Stinard
 
 
 
 

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