The single Emphasis Type="Italic"Andigenum/Emph

Authors: Marc Ghislain Jorge Núñez María del Rosario Herrera David M Spooner

Publish Date: 2009/01/09

Volume: 118, Issue: 5, Pages: 963-

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Abstract

NeoTuberosum refers to cultivated potato adapted to longday tuberization and a syndrome of related morphological and physiological traits developed by intercrossing and selection of shortday adapted potatoes of the Solanum tuberosum Andigenum Group native from the Andes of western Venezuela to northern Argentina This recreation of the modern potato helped support the theory of an Andigenum Group origin of potato in temperate regions and the possibility to access the largely untapped diversity of the Andigenum Group germplasm by base broadening breeding This NeoTuberosum derived theory the recreation of the modern potato from Andigenum germplasm has been universally accepted for almost 40 years and has had tremendous impact in planning some breeding programs and supporting phylogenetic conclusions in cultivated potato We show with microsatellite simple sequence repeat SSR and plastid DNA marker data that NeoTuberosum germplasm is closely related to Chilotanum Group landraces from lowland southcentral Chile rather than to Andigenum Group germplasm We interpret this quite unexpected result to be caused by strong rapid selection against the original Andigenum clones after unintended hybridization with Chilotanum Group germplasm In addition we show that NeoTuberosum and Andigenum Group germplasm did not serve to broaden the overall genetic diversity of advanced potato varieties but rather that NeoTuberosum lines and lines not using this germplasm are statistically identical with regard to genetic diversity as assessed by SSRs These results question the longstanding NeoTuberosum derived theory and have implications in breeding programs and phylogenetic reconstructions of potatoThe origin of the “European” potato cultivated potato first appearing in Europe and then spreading worldwide has been controversial for nearly a century since the Russian potato scientists Juzepczuk and Bukasov 1929 supposed it as derived from landraces of Chilean origin growing at Chiloé Island and the Chonos Archipelago to the south The morphological resemblance and the capacity to tuberize under longday conditions were the two main arguments for a Chilean origin The tetraploid cultivated potato Solanum tuberosum has been long recognized as divided into two entities either referred to as species Bukasov 1971 Lechnovich 1971 subspecies Hawkes 1990 Ochoa 1990 or Cultivar Groups Dodds 1962 Huamán and Spooner 2002 Spooner et al 2007 S tuberosum Andigenum Group is distributed from western Venezuela south to northern Argentina and S tuberosum Chilotanum Group formerly referred to as the Tuberosum Group from lowland Chile in Chiloé Island and the islands of the Chonos Archipelago to the south Huamán and Spooner 2002 For simplicity of discussion in this paper we refer to S tuberosum Andigenum Group as “Andigenum” and S tuberosum Chilotanum Group as “Chilotanum” referred to as Tuberosum in most potato breeding literature Andigenum germplasm tuberizes poorly in the long days of the temperate latitudes and the ability to rapidly select Andigenum for longday length tuberization has been a big part of the longstanding controversy on the origin of the European potato Ames and Spooner 2008In contrast a number of potato scientists proposed or supported an Andigenum origin of the European potato Salaman 1937 Salaman and Hawkes 1949 Glendinning 1975b Hosaka and Hanneman 1988 This longstanding view was based partly on the production of NeoTuberosum potatoes and on a range of other historical arguments Ames and Spooner 2008 In 1959 Simmonds initiated a longterm experiment at the John Innes Institute to select modern potato characteristics from germplasm of exclusive Andigenum origin Simmonds 1966 He started with 3300 seedlings of about 300 Andigenum accessions from geographically wide sources in Colombia Peru and Bolivia He bred these through two sexual generations in a field with open pollination and mass selected them for 5 years primarily for daylength adaptation as expressed by greater tuber production in the long days of the UK At the end of the experiment he produced a population he designated to be “half way” from the original Andigenum to Chilotanum relative to a range of characters that he referred to as the “day length syndrome” These included earlier tuberization fewer and shorter stems less flowering shorter stolons greater yield larger leaves less pigmented smoother tubers fewer but larger tubers fewer seeds per fruit and late blight and virus X and Y resistance Simmonds 1969 named this new advanced potato germplasm “NeoTuberosum” The material was later transferred to the Scottish Crop Research Institute where it was further intercrossed Glendinning 1975a and characterized with respect to Andigenum and Tuberosum traits Glendinning 1975b Similar to previous observations by Simmonds 1966 NeoTuberosum appeared to have intermediate characteristics between Andigenum and Chilotanum It was shown to be a highly diverse set of germplasm with a wide range of desirable traits that was thought to be lacking in existing advanced cultivars such as viruses X and Y and wart resistance provided by the Andigenum germplasm Glendinning 1975cThe ability to rapidly adapt Andigenum germplasm to a Chilotanumlike form and day length response was used as one part of a multicomponent argument supporting Andigenum germplasm rather than Chilotanum germplasm as the progenitor of the European potato Hawkes 1956 Simmonds 1978 Hosaka and Hanneman 1988 The Chilean origin hypothesis Juzepczuk and Bukasov 1929 was relegated to history and the Andigenum origin was universally accepted for the past 40 yearsThe late blight epidemic beginning in the UK in 1845 was seen as a turning point in shifting from the initial Andigenum introductions to Chilotanum introductions which through interbreeding gave rise to modern cultivars being hybrids of the two Cultivar groups There were many problems with this theory including general lack of late blight resistance in Chilean germplasm Bukasov 1933 Glendinning 1975d Jansky 2000 and cytoplasmic male sterility of the Chilotanum serving mainly as female Grun 1979 The incompatibility is especially significant because well over 99 of modern cultivars contain Chilotanum cytoplasm Corriveau and Coleman 1988 However this incompatibility is not absolute and many modern varieties produce pollen and can serve as a male breeding sourceNeoTuberosum development was quickly envisioned as a valuable prebreeding program useful to gain access to the wide Andigenum diversity of traits not easily found in Chilotanum landraces or modern cultivars by eliminating the unfavorable characteristics which had impaired its use in breeding in the past Simmonds 1966 1993 It inspired a new generation of potato breeders to practice the concept of germplasm enhancement by base broadening breeding using NeoTuberosum and the Andigenum landraces germplasm Glendinning 1975c In 1965 the potato breeding program at Cornell University took over the material from John Innes Institute and bred it with Andigenum landraces from South America Plaisted 1972 Rasco et al 1980 Muñoz and Plaisted 1981 After several years of breeding and selection this program provided NeoTuberosum material to many breeding programs worldwide including the International Potato Center CIP in Lima Peru The latter institution developed advanced breeding lines with resistance to early blight late blight viruses X and Y and important progenitors of true potato seeds FernandezNorthcote et al 1986 However not all breeding programs in particular private ones adopted the concept of base broadening using NeoTuberosum and Andigenum germplasm shading already doubts about the real impact on varietal improvement

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