150 accessions of breadfruit [Artocarpus altilis (Parkinson) Fosberg and A. mariannensis Trècul] and interspecific hybrids from 18 Pacific island groups were analyzed for isozyme variation. Six enzyme systems (ACO, ADH, IDH, MDH, ME, PGM) produced well-resolved bands Each accession was scored for presence or absence of bands for each enzyme system. Breadfruit is clonally propagated and numerous diploid and triploid cultivars are grown in the Pacific islands. Diploid cultivars of A. altilis from Melanesia and western Polynesia showed the highest variation. Few diploid cultivars were found in eastern Polynesia. Seedless, triploid cultivars showed identical banding patterns for all enzyme systems. The narrow genetic variation in triploid cultivars indicates that they are the result of repeated vegetative propagation of a naturally occurring triploid. In contrast, these cultivars exhibit great morphological variation due to somatic mutation, maintained through human selection. A. mariannensis and hybrid cultivars showed greater variation and were identifiable by unique banding patterns for ADH and MDH.
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