tl

 

tl (clavicula ortendril-less)

The 'tl' mutation is commonly called the 'acacia' mutant, because the leaf shape of this mutant resembles leaves of the genus Acacia. Tendrils of plants with this mutation are converted into leaflets, so that true tendrils are absent on such plants. Because of this absence of tendrils, plants with the acacia phenotype do not "vine" the way regular pea plants do, and they therefore have problems "standing" in a field. This problem is especially pronounced in plants that also have the fasciatagene, which causes plants to be "top heavy".

This gene has been the subject of several studies of gene interaction, when studied with the afila (af) mutation. Afila conditions a seemingly opposite phenotype, when it converts leaflets to tendrils, which results in leaves composed entirely of tendrils. Acacia leaves are composed entirely of leaflets. An intereseing thing happens when you cross a plant with the afila mutation with a plant that has the acacia mutation. Progeny from later generations that express both mutations have a leaf morphology that is commonly called the 'Parsley' morphology. Such plant's leaves resemble that garnish in that the leaflet/tendril structures appear to begin to develop into tendrils, but at the terminus of each tendril there develop tiny leaflets. An image of an af/tl "Parsley" phenotype can be found by clicking here.

The dominant 'Tl' allele is actually incompletely expressed in heterozygous plants, in a subtle way, where tendrils of heterozygotes appear to be markedly flattened. The locus for this gene maps to linkage group V. This phenotype was first found as a spontaneously occurring event in 1917. In this collection, 33 accessions are listed as having the 'tl' mutation, and another 32 accessions are mixed for this trait. If you would like to query for this mutation, click here.