Maize Genetics Cooperation Newsletter vol 86 2012

URBANA, ILLINOIS

USDA/ARS/MWA

Maize Genetics Cooperation � Stock Center

brachytic3 is allelic to brevis1.

--Stinard, PS

James Brewbaker recently indicated in an email to the Maize Genetics Stock Center that the phenotypes of the mutants br3 and bv1 in an Hi27 inbred background are nearly identical, and he asked us whether we had ever conducted a test of allelism between them. Both mutants map to chromosome 5, but they had never been tested against each other. To resolve this question, we set up crosses to test allelism in our 2011 winter nursery. We included na2 in our tests as well since it has a short plant stature and also maps to chromosome 5. The crosses were set up as follows: Known heterozygotes for br3 in coupling with pr1, known heterozygotes for bv1 in coupling with pr1, and known heterozygotes for na2 in coupling with pr1 were intercrossed in all possible combinations. Homozygous pr1 (red) kernels from each ear were planted in the observation block of our 2012 summer nursery, and observed at maturity. Progeny grown from the cross of br3 heterozygotes by bv1 heterozygotes segregated for brachytic (brevis) plants in a high proportion due to coupling with pr1. Crosses of br3 heterozygotes to na2 heterozygotes and crosses of bv1 heterozygotes to na2 heterozygotes resulted in nonmutant progeny. We conclude therefore that br3 and bv1 are allelic, and na2 represents a separate locus. Since bv1 (first report Li, HW. 1931. J Hered 22:14-16) has precedence over br3 (first report Singleton, WR. 1959. MNL 33:3-4), the br3 locus has been lapsed and the br3 data has been merged with the bv1 data in MaizeGDB. The old br3 reference allele is now called bv1-br3.

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