MORPHOLOGICAL AND CYTOLOGICAL IDENTIFICATION OF THE PRIMARY TRISOMICS OF LOTUS PEDUNCULATUS (LEGUMINOSAE)

Abstract

Trisomics have been developed in the diploid species Lotus pedunculatus Cav. (2n = 12) by means of a series of hybridizations. From the progeny of crosses of triploids to the diploid and selfing triploids, 126 (62.38%) diploids, 73 (36.14%) simple trisomics, 2 (0.99%) double trisomics and 1 (0.49%) telosomic trisomic were obtained. The simple trisomic plants were classified into five distinct morphological groups named Round, Broad, Pointed, Narrow and Small according to their distinguishing leaflet characters. Each group differed from the others and from the diploid in a number of qualitative and quantitative characters. These differences were considered to be the result of a change in the genic balance of the plants which was brought about by the addition of the extra chromosome to the complement. The extra chromosomes of Round, Broad, Pointed, Narrow and Small were identified as chromosomes 1, 3, 4, 5, and 6, respectively. Although the frequency of cells with one trivalent varied within and between trisomic types, there was a positive correlation between length and trivalent formation. It is considered that longer chromosomes have a greater chance of forming chiasmata with more than one homologue than shorter ones. The frequency of lagging chromosomes at AI and/or TI was not correlated with the frequency of univalents at diakinesis. No particular trend was apparent as to which extra chromosome, when present as a lagging chromosome, tended to divide more frequently than another chromosome of the complement.