MOLECULAR SUPPORT FOR THE HYBRID ORIGIN OF THE WILD POTATO SPECIES SOLANUM X RECHEI

Twenty-seven of the 232 wild potato species (Solanum sect, Petota) hav e been hypothesized to be of natural hybrid origin. Prior molecular da ta have failed to support hybrid origins involving two other wild pota to species, Solanum raphanifolium Cardenas and Hawkes and S. chacoense Bitter, and hybrid speciation has never been supported with molecular data in sect, Petota. This study was conducted to test the hybrid ori gin of Solanum x rechei Hawkes and Hjert. It is a locally common and w eedy wild potato species from Argentina, occurring at the extreme sout hern end of the range of S. microdontum Wittm., and near the northern end of the range of S. kurtzianum Bitter, its two putative parents. So lanum x rechei is diploid (2n = 2x = 24) with triploid (2n = 3x = 36) populations, S. kurtzianum is diploid (2n = 2x - 24), and S. microdont um is diploid (2n = 2x = 24), with diploid populations at its extreme southern range. A Drier study supported the hybrid origin of S. x rech ei by intermediate morphology of natural and synthetic hybrids, reduce d pollen stainability of the natural and synthetic hybrids, and distri butional evidence. but studies of ne iv collections and prior germplas m collections fail to support the morphological intermediacy of S, x r echei, but lack of morphological intermediacy is common for many hybri ds. Hybrid origin was instead verified by reduced pollen stainability and additive parent-specific single- to low-copy nuclear restriction f ragment length polymorphisms (RFLPs) in S. x rechei. These data sugges t that other wild potato species also may be of hybrid origin, which m ay help explain some of the taxonomic confusion in the group.