Description and mapping of the tassel-less (tls1) mutation
--M. C. Albertsen, M. R. Trimnell and T. W. Fox

Woodworth (J. Hered. 17:405-411) published a description of a "barren-sterile" mutant in 1926. This mutant was described as exhibiting an "inhibition...of sex, since neither tassel nor ear is produced". Because neither a tassel nor an ear was produced, it was described as being both "barren" and "sterile". The mutant was designated bs1. The mutation was never mapped and seed stocks apparently were lost. MCA was given seed stock for a similar mutant in 1976 by Dr. Robert .i.Brawn, R;, then of Funk Seeds International. Dr. Brawn had referred to the mutant as "tassel-less". This mutant was derived from Minn Syn 3 and segregated mostly as a single gene recessive. In its original nuclear background, plants homozygous for the mutation were distinguishable at the 4-8 leaf stage. These plants appeared more pubescent than normal sibs and the leaves had a leathery look and texture, which seemed to impart an olive-green cast to the plants. In other nuclear backgrounds, e.g. A632, these differences are greatly diminished. Homozygous mutant plants generally do not develop tassels, although ear shoots are produced. Generally, however, no ears develop within the husk tissue. Mutant expression is variable, especially among progeny from selfing a heterotic cross. Tassel-like structures can be obtained that vary from having only a couple of spikelets to having a more complete looking tassel. Ear development also can vary from a structure on which only a few kernels develop to a structure that resembles a 'Strawberry Pop' type of ear. The amount of ear development is not necessarily correlated with the amount of tassel development, nor vice versa.

We chose to designate this mutation as tassel-less, tls1. It is most likely the same mutation as that described by Woodworth, as his J. Hered. photographs and description match our mutant exactly. Still, without the original seed stocks, we could not make the allelism crosses. We chose to call the mutation tls1 because it seemed generally to best describe the most striking feature of the mutation, that of a missing tassel.

We crossed homozygous mutant plants that had been selected to produce small 'Strawberry Pop'-type of ears as female with an A-B interchange series. F1 progenies were grown in our Hawaii nursery in 1991. Although all chromosome arms were not covered, we determined that the likely location for the mutation was on chromosome 1L (Table 1). We subsequently interval mapped this mutant using the following RFLP probes on chromosome 1: bnl8.10, bnl7.25, bnl8.29, php15058, php20557, bnl6.32. Twenty normal sibs and 12 tls1 plants were bulked by phenotype. Differential polymorphisms were observed with probes bnl8.29, php15058, php20557, and bnl6.32. This agrees with the A-B interchange results and locates the mutation to the distal one third of chromosome 1L.

Table 1. Location of tls1 to chromosome 1L using homozygous TB-1Lc crossed onto homozygous tls1 plants selected for ear development.
 
No. hypoploid plants
No. tls1 hypoploids No. normal plants
11 11 80


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