The 2C nuclear DNA amounts were determined for 99 accessions, represen
ting 23 Arachis species from 8 of 9 taxonomic sections, and two synthe
tic amphidiploids. Mean 2C DNA amounts varied by 15.20%, ranging from
10.26 to 11.82 pg, between accessions of Arachis hypogaea (2n=4x=40).
Nuclear DNA content variation (5.33-5.91 pg) was also detected among A
rachis duranensis (2n=2x=20) accessions. The intraspecific variation i
n the two species may have resulted from indirect selection for favour
able genome sizes in particular environmental conditions. The accessio
ns belonging to A. hypogaea ssp. hypogaea (mean value 11.27 pg) with l
onger life cycle had significantly larger mean DNA content than the ac
cessions of A. hypogaea ssp. fastigiata (mean value 10.97 pg). For 20
diploid (2n=2x=20) species of the genus, 2C nuclear DNA amounts ranged
from approximately 3 to 7 pg. The diploid perennial species of sectio
n Arachis have about 12% more DNA than the annual species. Comparisons
of DNA amounts show that evolutionary rating is not a reliable guide
to DNA amounts in generic sections of the genus; lower DNA values with
evolutionary advancement were found in sections Heteranthae and Trise
minatae, but the same was not true for sections Arachis and Caulorrhiz
ae. Similarly, there is evidence of significant differences in DNA con
tent between 4 ancient sections (Procumbentes, Erectoides, Rhizomatosa
e, and Extranervosae) of the genus. The occurrence of genome size plas
ticity in both A. duranensis and A. hypogaea provides evidence that A.
duranensis could be one of the diploid progenitors of A. hypogaea. Th
e DNA content in the two synthetic amphidiploids corresponded to the s
um value estimated for parental species.