A recessive barren-inflorescence mutation

--Steve Briggs & Guri Johal

A mutation that resembles Bif1 has been observed in our Mutator stocks. In contrast to Bif1, our mutant (bif*-47330) appears to be fully recessive; 18 of 75 plants in an F2 family displayed the mutant phenotype. Mutants are easily spotted in the field because the tassel has few or no branches and is unusually thin, with the thinness beginning at the first node that fails to produce a leaf. The principal effect of the mutation may be to limit spikelet development. Failure to produce spikelets results in a bare or hairy ridge on the cob where a cupule would normally be. The size of these sterile sectors varies from one cupule to nearly the entire ear. The tassel is similarly modified. Tassel spikelets are typically unpaired, with only the pedicillate spikelet developing (occasionally a vestigial or normal sessile spikelet is observed). The tassel spikelet pedicels are much elongated (to about 1cm) and the spikelets themselves are about twice normal size. The florets appear normal but shed poorly or fail to shed. Occasional ears are found that show an unpaired phenotype, either as a sector or as the entire ear. Possibly the sessile spikelet in the ear is suppressed congruent with the tassel phenotype. These observations suggest that the mutation may reduce the amount of a factor that is required for the development of spikelets, with the sessile spikelet being more sensitive to this reduction than is the pedicillate spikelet.

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