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Title: DNA from herbarium specimens settle a long-held controversy about origins of the European potato

Author
item AMES, MERCEDES - UNIV OF WI MADISON
item Spooner, David

Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2007
Publication Date: 1/25/2008
Citation: Ames, M., Spooner, D.M. 2008. DNA from herbarium specimens settle a long-held controversy about origins of the European potato. American Journal of Botany. 95:252-257.

Interpretive Summary: There are two classes of cultivated potato. One class is indigenous “unimproved” forms called landraces cultivated for millennia by native farmers in South America, and the other class is improved modern potatoes first appearing outside of South America in Europe in 1567 and later cultivated worldwide – the “European” potato. The South American landraces occur in two areas. One is a broad region of the high Andes from Venezuela to Argentina, and the other region is from the lowlands of south-Central Chile. There has been a long-standing controversy about the origin of the European potato, one group supporting origins from Chile, and the second group supporting origins from the Andes. All data supporting one argument or the other has been secondary inferential; arguments. The present paper provides the first direct evidence to this question by identifying introductions from these two places by genetic material (DNA) extracted from old preserved material called herbarium specimens. Here we show, through DNA characters characteristic of Chilean potato, that the Andean type was predominant in the 1700’s but the Chilean potato was introduced into Europe as early as 1811 and became the predominant type long before late blight disease in Europe. Our results provide the first unambiguous answers to the long-debated questions of the origin of the European potato, and highlight the critical importance of herbarium specimens in investigating historical introductions of crop plants.

Technical Abstract: Landrace potato cultivars (Solanum tuberosum L.) are native to two areas in South America: the high Andes from Venezuela to Argentina, and the lowlands of south-Central Chile. Potato first appeared in Europe in 1567, and rapidly diffused worldwide. Two competing hypotheses have suggested the origin of the “European” potato from the Andes or from Chile, but the Andean origin has been widely accepted over the last 60 years. All modern potato cultivars are the Chilean type, and are explained as introductions from Chile subsequent to the late blight epiphytotics beginning in 1845 in the UK. The Andean introduction hypothesis has been questioned recently through molecular identifications of extant and putatively remnant early introductions from South America as the Chilean type, but all evidence to date on the first European potato has been inferential. Here we show, through surveys of a 241-bp plastid DNA deletion marker characteristic of Chilean potato from early herbarium specimens, that the Andean type was predominant in the 1700’s but the Chilean potato was introduced into Europe as early as 1811 and became the predominant type long before late blight disease in Europe. Our results provide the first unambiguous answers to the long-debated questions of the origin of the European potato, and highlight the critical importance of herbarium specimens in investigating historical introductions of crop plants.