Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

CHARACTERIZATION OF LOTUS SPP. BY ANALYSIS OF THE ITS REGION

MARIANI A., BOLIS A.

IRMGPF-CNR, Via della Madonna Alta 130, 06128 Perugia

Anna.Mariani@irmgpf.pg.cnr.it

Lotus, ribosomal spacers, PCR, phylogenesis, breeding

The genus Lotus comprises both annual and perennial species adapted to a wide range of ecological habitats. Those species form a complex of closely related groups with very similar taxonomic characters, so that it is very difficult to identify the different species or types. Birdsfoot trefoil (Lotus corniculatus L.) is recognised as having outstanding agricultural value mainly because of the condensed tannins it contains and because it has the widest distribution of all Lotus species, and a remarkable capacity to adapt to widely differing environments. Despite the importance of that species, very little is known about its evolution, its cytotaxonomy and its cytogenetics, probably because L. corniculatus is a highly polymorphic species for many characters.

Studies covering such aspects as morphology, tannin and phenol contents, cytogenetics and self-incompatibility in Lotus spp. have suggested that L. corniculatus (2n=4x=24) originated from the hybridisation of L. alpinus Schleich. or L. tenuis, both diploids (2n=2x=12), with the diploid L. uliginosus, followed by chromosome doubling. More recently, however, researchers have tended to exclude any involvement of L. uliginosus, and attention has instead been focused on L. alpinus, which has in turn been considered to be a sub-species of L. corniculatus, or its probable ancestor, or a diploid type adapted to high mountainous areas.

Studies on Lotus populations from Alpine areas are of special interest because diploid (2n=12) and tetraploid (2n=24) types have been found distributed along different transects. The two cytotypes were first described as two distinct species. Subsequently they were identified as two variants of the same species despite differences in their morphological, chromosomal and ecological characters. Furthermore, in some altitudinal zones, diploid and tetraploid types have been observed which had the same morphological characteristics and should therefore be considered as probably belonging to the same species.

The great agricultural value of Lotus as a fodder crop on the one hand, but also its extremely confusing taxonomy on the other hand, are two opposed reasons why we felt the need for a reliable characterization of its various species. This, in fact, is a necessary condition for establishing their phylogenetic relationships and their potentialities for the purpose of selecting the best materials to be used for breeding programs.

Since cytotaxonomy and even cytogenetics both failed to clearly identify the Lotus species, we thought it necessary to use a molecular approach.

While the coding region of the rDNA repeat unit is highly conserved within and among species, the internal transcribed spacer region (ITS) and the intergenic spacer of this repeat unit evolve faster and may vary among species within the same genus or among populations. Therefore, as a first attempt to distinguish among Lotus species we are cloning and sequencing the PCR-amplified ITS region from different accessions of each of the species under investigation (L. corniculatus, L. alpinus, L. tenuis and L. angustissimus). Moreover, the direct sequencing of that region will allow us to test for the presence of intragenotypic variability. Preliminary results for one accession of each single species show a remarkably high sequence similarity among L. alpinus, L. tenuis and L. corniculatus. However, L. alpinus seems to have closer similarity to L. corniculatus than to L. tenuis.