Maize Genetics Cooperation Newsletter vol 85 2011

New alleles of enr1 and enr2.

‑‑Stinard, PS

Stinard (2007. MNL 81:33-35) describes two r1 haplotype-specific enhancers of aleurone color isolated from an accession of R1-r(Venezuela459#16039) from the Brink r1 haplotype collection donated to the Maize Genetics Stock Center by Jerry Kermicle. The enhancers were linked, with a separation of 25.2 centiMorgans; one enhancer, Enr*-459A, expressed equally well in male and female outcrosses with susceptible r1 haplotypes and the other enhancer, Enr*-459B, expressed only in female outcrosses. Chromosomal location was unknown, and their relation to the characterized enhancer loci enr1 and enr2 (Stinard et al. 2009. The maize enr system of r1 haplotype-specific aleurone color enhancement factors. J Hered 100:217-228) was not known. Stinard et al. (2009) found enr1 and enr2 to be separated by 23.4 centiMorgans in direct linkage tests and expression patterns of Enr1 and Enr2 alleles match that of Enr*-459A and Enr*-459B respectively. Linkage tests of Enr*-459A and Enr*-459B were subsequently performed with enr1 and enr2 and the results are reported here.

Since the phenotype of Enr*-459A most closely matches that of Enr1 alleles with respect to good expression in both male and female outcrosses, it was mapped only with respect to enr1. A homozygous r1-g(Stadler) Enr*-459A line was crossed to a homozygous r1-g(Stadler) Enr1-628 line, and F1 plants were outcrossed as males to responsive homozygous enr1 R1-r(Venezuela559-PI302355) testers. The parental classes and the double factor recombinant class would be expected to have full color aleurones, and the recombinant class lacking both factors would be expected to have pale aleurones. Kernels from these crosses were scored for aleurone color, and exceptional pale or colorless kernels were subsequently planted and the resulting plants selfed and outcrossed to enr1 R1-r(Venezuela559-PI302355) testers to confirm genotypes. Of 13 exceptional kernels obtained from a population of 5166 kernels, only 7 could be tested and all were found to be parental types. Therefore, no recombinants were found from an effective population of 2872 kernels, indicating a separation of less than 0.07 +/- 0.05 centiMorgans. We conclude that Enr*-459A and Enr1-628 map to the same location and are most likely allelic. Enr*-459A has been renamed Enr1-459A.

The female-only expression of Enr*-459B matches that of other Enr2 alleles and therefore Enr*-459B was mapped only with respect to enr2. A homozygous Enr*-459B R1-r(Venezuela559-PI302355) line was crossed to a homozygous Enr2-694 R1-r(Venezuela559-PI302355) line, and F1 plants were crossed as females by homozygous enr2 R1-r(Venezuela559-PI302355) testers. The parental classes and the double factor recombinant class would be expected to have full color aleurones, and the recombinant class lacking both factors would be expected to have pale aleurones. Kernels from these crosses were scored for aleurone color, and exceptional pale kernels were subsequently planted and the resulting plants crossed as females by enr2 R1-r(Venezuela559-PI302355) testers to confirm genotypes. Of 3 exceptional pale kernels obtained from a population of 3712 kernels, only 2 could be tested and both were found to be parental types. Therefore, no recombinants were found from an effective population of 2475 kernels, indicating a separation of less than 0.08 +/- 0.06 centiMorgans. We conclude that Enr*-459B and Enr2-694 map to the same location and are most likely allelic. Enr*-459B has been renamed Enr2-459B.

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