Karyotype analysis and relationships among varieties of Arachis hypogaea L.

Mitotic chromosomes of nine Arachis hypogaea L. cultivars plus A. monticola Krap. et Rig. were analyzed cytologically. The cultivars included representatives of the four botanical varieties of A. hypogaea. The objective of this investigation was to identify the chromosomes of cultivated peanuts and determine the variation among subspecies and varieties. The A. hypogaea chromosomes ranged in length between 1.44 and 4.17μm and were mostly metacentric. Variation was observed in the numbers of asymmetrical chromosomes per cultivar and in the chromosome with a secondary constriction. Based on heterochromatic regions, centromere positions, and chromosome lengths, homologues were identified and ordered from 1=longest to 20=shortest. Although each genotype had a unique karyotype, patterns of variation were observed and all A. hypogaea varieties were cytologically disting-uished. Varieties vulgaris and hypogaea were karyologically the extreme groups with other varieties being intermediate. The cultivar nambyquarae is grouped kary-ologically with var. fastigiata even though it is a member of subspecies hypogaea. Arachis monticola was karyologically more similar to variety vaulgaris than other groups of A. hypogaea. This suggests that the variety vulgaris cultivars may be the most ancient A. hypogaea group.