Characterisation of alien chromosomes in monosomic additions of Beta

<p>Wild <em>Beta</em> species of the section <em>Procumbentes</em> carry genes for several valuable agronomical traits, and are considered to be of interest for the breeding of cultivated beet <em>(B. vulgaris</em> subsp. <em>vulgaris).</em> In spite of several barriers, it was shown that gene transfer from <em>B</em> . <em>procumbens</em> into sugar beet is possible. In such studies monosomic additions (2n=19) in <em>B. vulgaris,</em> harbouring different individual chromosomes of the wild species, play a very important role. To select the monosomic addition plants, an extensive number of different <em>B.</em><em>procumbens</em> or <em>B. patellaris</em> derived monosomic addition families were screened, using repetitive DNA sequences and a squash-blot hybridisation procedure. The extra chromosomes of the monosomic additions were identified with the aid of DNA fingerprinting. In <em>B</em> . <em>procumbens</em> derived monosomic additions, the chromosome numbers of two additions had to be renamed. Seventyfive anonymous <em>B.</em><em>patellaris</em> derived monosomic additions were grouped in nine different groups, many of them with two sub-groups. The. morphological characteristics of the plants of the nine different groups of monosomic additions of <em>B. patellaris</em> were described and comparisons were made between these groups and the monosomic additions of <em>B.</em><em>procumbens.</em> Chromosome characterisation also was studied using fluorescence <em>in situ</em> hybridisation on mitotic chromosomes and extended DNA fibres of a series of monosomic additions of <em>B. procumbens.</em> The monosomic additions were evaluated in greenhouse tests for resistance to the beet cyst nematode <em>(Heterodera schachtii), Cercospora beticola, Polymyxa betae</em> and BNYVV. These experiments permitted the localisation of major genes for resistance on specific chromosomes, and the study of some quantitative effects.