Primary Trisomics in Sugarbeet. I. Isolation and Morphological Characterization 1

All nines sugarbeet ( Beta vulgaris L.) primary trisomic types were established from a total of 48 trisomic plants isolated in the progeny of autotriploids of two closely related sugarbeet lines, one homozygous annual and one inbred biennial. Based on morphology, 42 of these trisomic plants were classified into eight morphologically distinct groups. Cytological identification of the extra chromosome of these eight group as and of the ninth type was accomplished by karyotype analysis in somatic cells. Ten leaf and petiole measurements were taken on 3‐ to 4‐month‐old plants grown in two different environments. Although significant differences existed between diploid and trisomic types, and any two trisomic types differed by at least three variables, no single trait could distinguish more than four groups of trisomic types. Discriminant analysis was performed on leaf measurements for seven trisomic types and their diploid sibs. For these closely related lines it was found that the discriminant functions classified most plants (97%) correctly within a given environment. However, the value of the measurements depended on the specific environment where the trisomics were grown, and only 44% of the leaves of diploid and trisomic plants grown in a second environment were correctly classified using the discriminant functions of the first environment. This fact precludes the use of the same discriminant functions for classification purposes over a series of different environments, although these functions might be useful in a standard controlled environment.