MULTIPLE DIFFERENTIATION OF PLASMONS OF DIPLOID SPECIES OF SOLANUM

Abstract

1959) have demonstrated that heritable plasmon variations exist and are of evolutionary importance. A further understanding of the role of plasmon variations will require a method for tracing the consecutive steps through which plasmon changes occur. This, in turn, will require that one be able to identify the individual unit characters of which a given plasmon is composed and formulate what might be termed a plasmantype, or description of a plasmon. The analysis presented here is the first step of an attempt to describe such plasmon characters of diploid tuber-bearing species of Solanum. These plants have the advantage that a considerable number of closely related species can be crossed (SWAMINATHAN and HOWARD 1953; HAWKES 1956a; HOWARD 1960; GRUN 1961) to produce fertile hybrids and, therefore, a diversity of genetic and plasmon types can be subject to test. Terminology One roadblock to analysis of plasmons is posed by our present lack of a symbol system to describe multiple characteristics of the same Dlasmon. Designations as generally used have identified plasmons by naming their sources or places of origin rather than by describing their characteristics. The individual plasmon characters dealt with here were identified by their interactions with specific genes. It was, therefore, decided to identify each plasmon character by the symbol used to designate the gene with which it interacts. The following example can be used to illustrate the method: A gene has been found which causes deformed flowers when it is present in the homozygous recessive condition and in a plasmon sensitive to its action. The gene for the deformed flowers was designated by the symbol df, and its allele for normal flowers of. The sensitive plasmon was designated dfe, the lower case letter being used since it interacted with the reces-sive allele of the gene, and the superscript s inserted to indicate that the plasmon 1Authorized for publication April 9, 1962 as paper No.