San Diego, California

University of California

barren stalk1 is epistatic to teosinte branched1 --Ritter, MK, Padilla, CM, Schmidt, RJ Plants homozygous for the recessive barren stalk1 (ba1) mutation, first described by Hofmeyr in 1930, are characterized by having a tassel which lacks branches and spikelets. These plants also have no ears or tillers. To establish whether the lack of tillers in ba1 mutants is due to true suppression of vegetative branching or to background effects, a double mutant was generated with teosinte branched1 (tb1), a mutation which causes excess tillering.

Plants heterozygous for the ba1 mutation were crossed to homozygous tb1 mutants and the resulting F1 progeny were then selfed. F2 populations were screened to determine which ones segregated for the ba1 and tb1 phenotypes. Two hundred and thirty seven F2 progeny were genotyped at the tb1 locus by Southern blots with a genomic tb1 probe. (Probe kindly provided by John Doebley). Of these 237 F2 plants, 47 were tb1 homozygous mutants. Eleven of those 47 tb1 mutants also showed the ba1 phenotype. Due to the fact that these ba1/tb1 double mutant plants shed a small amount of pollen, one of these 11 plants was crossed to a heterozygous ba1 tester to confirm the presence of the ba1 allele. Ten progeny were planted from this cross, of which 6 showed the ba1 phenotype.

The tb1/ba1 double mutant is indistinguishable from the ba1 single mutant (Figure 1). Thus it appears that ba1 is epistatic to tb1 and completely suppresses lateral branching in both the vegetative and inflorescence meristems.

Figure 1.

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