1936 Volume 7 Issue 3 Pages 396-423
1. A consideration of the basic chromosome numbers present in the legume family indicate that A. hypogaea is a polyploid species.
2. The chromosome number of 115 out of 116 plants carefully examined representing 33 species, varieties, lines, F1, F2, and F4 varietal hybrids is reported as 20 (n) or 40 (2n). The exceptional plant contains 41 somatic ehromosomes and a small fragment. The 116 plants examined show the presence of 2 chromosomes morphologically distinguishable from the others because of their smaller size. This pair has been designated “A” One strain of a Spanish type, one of a runner type and 9 F4 plants of a Spanish×runner Cross (the only ones studied up to this time with an improved technique) show the presence of chromosome pair “A” and a second pair, the chromosomes of which possess a subterminal attachment constrietion and a conspicuous secondary constriction, here designated as pair “B” This pair is set apart from all the others by the subterminal rather than approximately median attachment constriction.
3. The cultivated peanut, A. hypogaea, is a species in which chromosome association during meiosis in varieties and varietal hybrids is usually seen as 20 normal bivalents. Other configurations such as trivalents, quadrivalents, quinquevalents, sexivalents, and an association of ten chromosomes are occasionally formed. It appears to be a species in which deviations from the 40 somatic number seldom occur.
4. No cytological evidence is encountered to oppose the view of Chevalier that the Rasteiro peanut and A. nambyquarae are at most subspecies of A. hypogaea.
5. The Problem of the origin of the bunch and runner type forms of the commercial peanut is discussed in the light of the cytological results. In that the chromosome number, morphology, and behavior of the bunch and runner peanuts are essentially similar, and the chromosomes of these two peanut types are seen to be homologous each to each notwithstanding minor changes that may have taken place, it is concluded that they, as well as A. nambyquarae and A. Rasteiro have been derived from a common origin.
I wish to thank those who so generously shared seed and Dr. Orland E. White, Director of the Blandy Experimental Farm, who has made this study possible and has kindly contributed helpful advice during the course of the investigation and a final criticism of the manuscript.