A Frequently Mutating Gene in the Pineapple Ananas Comosus (L.) Merr

The spiny-leaved plants and the spiny-smooth chimera plants which are found in Cayenne fields originate as somatic mutations. The percentage of chimera plants was found to be smaller in the Cayenne variety, which genetic tests had indicated as being hybrid for spiny leaves, than in smooth-leaved hybrid plants produced by crossing smooth-leaved with spiny-leaved varieties. This difference, it is believed, may be due to homozygous smooth-leaved plants in the Cayenne population which do not produce chimeras. A clon derived from a hybrid plant homozygous for smooth leaves contained no chimeras when a similar sized population of heterozygous plants would have contained 43 chimeras. A method is outlined by which homozygous Cayenne plants can be identified if they exist in the variety. The rate of mutation from smooth to spiny in the pineapple, 4.95 per cent., places this in the category of frequently mutating or unstable genes.