It was recently noted that the old French INRA inbred line F1254 shows 4.5% of plants with two stalks. The duplication affects the mesocotyl, the coleoptile, and the primary seminal root. In the dormant seeds, the double plumules cannot be detected.

The appearance of such a trait is more regular than the phenomenon of "siamensis" reported by Sangueneti (1940, Anal. Inst. Fitotecn. Santa Catalina, Llavallol , Argentina, 17-134).

As far as the determination of the nature of this trait is concerned (true polyembryony or early fasciation taking place during embryogenesis), some heterozygous plants for the liguleless-1 gene were selfed. Among 37 plants with double stems, all couples were concordant either for liguleless leaves (8 plants) or normal leaves. The hypothesis of true polyembryony is then discarded, a minimum of 6 plants would have been enough at the P-0.05 level to find a seed with discordant stems. This trait with low incomplete penetrance is probably due to oligogenic control. After a cross with another donor line for a special gene (1gl su1, ...), a minimum of 4 backcrosses is needed to find again such a trait in the F1254 background.

M. Pollacsek

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