Nuclear and chloroplast DNA reassessment of the origin of Indian potato varieties and its implications for the origin of the early European potato

Abstract

The modern cultivated potato was first recorded in Europe in 1562, but its area(s) of exportation has long been in dispute. Two competing hypotheses have proposed an "Andean" area (somewhere from upland Venezuela to northern Argentina) or a lowland south central "Chilean" area. Potato landraces from these two areas can be distinguished, although sometimes with difficulty, by (1) cytoplasmic sterility factors, (2) morphological traits, (3) daylength adaptation, (4) microsatellite markers, and (5) co-evolved chloroplast (cp) and mitochondria (mt) DNA. The Chilean introduction hypothesis originally was proposed because of similarities among Chilean landraces and modern "European" cultivars with respect to traits 2 and 3. Alternatively, the Andean introduction hypothesis suggests that (1) traits 2 and 3 of European potato evolved rapidly, in parallel, from Andean landraces to a Chilean type through selection following import to Europe, and (2) the worldwide late blight epidemics beginning in 1845 in the United Kingdom displaced most existing European cultivars and the potato was subsequently improved by importations of Chilean landraces. We reassess these two competing hypotheses with nuclear microsatellite and cpDNA analyses of (1) 32 Indian cultivars, some of which are thought to preserve putatively remnant populations of Andean landraces, (2) 12 Andean landraces, and (3) five Chilean landraces. Our microsatellite results cluster all Indian cultivars, including putatively remnant Andean landrace populations, with the Chilean landraces, and none with the "old Andigenum" landraces. Some of these Indian landraces, however, lack the cpDNA typical of Chilean landraces and advanced cultivars, indicating they likely are hybrids of Andean landraces with Chilean clones or more advanced cultivars. These results lead us to reexamine the hypothesis that early introductions of potato to Europe were solely from the Andes.

Development of microsatellite markers in potato and their transferability in some members of Solanaceae

“…For example, K. Chamatkar and K. Kundan, both desired from Ekishirazu (Spooner et al, 2005) were placed together on the N-J tree drawn by us, but have been placed on separate branches by Spooner et al (2005). K. Jyoti is the common parent to K. Badshah, K. Swarna and K. Jawahar was shown by Spooner et al (2005) but, the same relationship could not be traced in the present study. On the other hand, K. Muthu though unrelated to K. Jyoti, has been placed closer by Spooner et al (2005) but not so in our N-J tree.…”

“…These differences can be attributed to the narrow genetic base of the genotypes used by Ashkenazi et al (2001) and in the present study. Spooner et al (2005) reported relatively poor allele numbers per microsatellite locus in Indian potato cultivars compared to other groups included in their study, suggesting a relatively narrow genetic base of Indian cultivars. It is believed that modern potato cultivars represent lower genetic diversity compared to landraces (Spooner et al, 2005).…”

“…Spooner et al (2005) reported relatively poor allele numbers per microsatellite locus in Indian potato cultivars compared to other groups included in their study, suggesting a relatively narrow genetic base of Indian cultivars. It is believed that modern potato cultivars represent lower genetic diversity compared to landraces (Spooner et al, 2005). The ability of microsatellites to distinguish different genotypes in a sample set characterized by a narrow genetic base advocates the utility of the newly discovered microsatellites.…”

“…3) and successfully distinguished all the 79 genotypes, it was not possible to decipher their phylogenetic relationships in a convincing way. Spooner et al (2005) used a subset of cultivars used in this study, and similarly found those cultivars clustered together using genomic and chloroplast DNA microsatellites. However, the phylogenetic relationships on the N-J tree reported by Spooner et al (2005) and in the present study do not fall in agreement with each other, as some of the close relatives in both the studies have been placed quite Neighbor-joining tree constructed from microsatellite marker analysis using Nei's (1972) similarity coefficient.…”

Molecular Studies on the Origin of the Cultivated Potato: A Review

“…Spooner et al (2005b) investigated the origin of potato cultivars (varieties) from India. Among these varieties were cultivars thought to be derived from S. tuberosum subsp.…”