Texas A&M University

Wrp: A new dominant dwarf mutation

--A.J. Bockholt and J.D. Smith

An unusual dwarf plant was found by A.J. Bockholt a few years ago in a composite population of Mexican maize races. The original plant was heterozygous, and, since no similar mutants were observed in this population before or since the plant was discovered, we believe it represented the original mutation.

Dominance for dwarfism is not complete. Homozygotes are about 14-20 inches tall, while heterozygotes are occasionally as tall as 3 feet. Both homozygotes and heterozygotes are capable of producing viable pollen and functional silks, although individual plants may be either male or female sterile. Silking tends to lag behind anthesis from a few days to a week or more. These tendencies are more pronounced in homozygotes, but selfed seed can be produced on some homozygous plants.

The most striking phenotypic characteristic of this mutation is the wrinkled appearance of the plant, which is more extreme in homozygotes than heterozygotes. The leaves appear to be longitudinally corrugated. This effect extends from the base of the leaf sheath to the tip of the leaf and even the culm in some plants.

Although we have not assayed these plants for gibberellins (GA), it seems unlikely that this mutation affects GA synthesis or functions. Dominance of the mutation rules out GA deficiency, and the wrinkled phenotype is very different from known GA-deficient or GA-insensitive mutations in maize (D8) and sorghum.

Thus, we propose to designate this mutant allele as Wrp, to distinguish it from GA related dwarfs. We have not yet mapped the Wrp locus, but small quantities of seed of this mutant can be supplied upon request.

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors

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