SPECIES BOUNDARIES AND INTERRELATIONSHIPS OF 2 CLOSELY-RELATED SYMPATRIC DIPLOID WILD POTATO SPECIES, SOLANUM-ASTLEYI AND SOLANUM-BOLIVIENSE, BASED ON RAPDS

The more than 200 wild and cultivated species relatives of potato (Sol anum sect. Petota) present a valuable germplasm base for cultivar impr ovement. However, species boundaries and interrelationships within sec t. Petota are controversial, inhibiting the efficient organization of the many germplasm collections of these species, One controversy invol ves questions of species boundaries and interrelationships of S. astle yi and S. boliviense. Solanum boliviense is narrowly endemic to two De partments in southern Bolivia, and S. astleyi is known only from one s ite entirely within the range of this species, where they co-occur. Bo th species are diploid and morphologically very similar. Artificial hy brids between them are fully fertile, and the species putatively hybri dize naturally. These data have been interpreted to designate them as separate species or as S. astleyi an ecotype of S. boliviense. Putativ e progenitors of S. astleyi are S. boliviense, S. megistacrolobum subs p. megistacrolobum, and S. megistacrolobum subsp. toralapanum. We eval uated interrelationships among these species with random amplified pol ymorphic DNA's (RAPDs) generated for 2 accessions of S. astleyi and 14 accessions of S. boliviense. These represent the entire geographic ra nge of the former species and nearly the entire range of the latter. W e also analyzed 1 accession each of S. acaule subsp. acaule, S. acaule subsp, aemulans, S. albicans, S. berthaultii, S. megistacrolobum subs p, megistacrolobum, S. megistacrolobum subsp. toralapanum, S. raphanif olium, S. sogarandinum, and S. sparsipilum. Phenetic analyses of the R APD data show S. astleyi and S. boliviense to form two distinct groups and to be more similar to each other than to any of the other species investigated, suggesting that S. astleyi and S. boliviense are sister taxa, The divergence of S. astleyi and S. boliviense relative to othe r species examined suggests that they are worthy of taxonomic recognit ion at the subspecies, rather than species level, and we propose the n ew combination S. boliviense subsp, astleyi.