Solanum jamesii

This page is a draft, part of our ongoing wild potato project. I’ll probably be adding information to the species pages through 2020 at least, but I’m making them public since they may be useful even incomplete.

Solanum jamesii

Common Name(s): Four Corners potato

Synonyms: none

Series: Pinnatisecta

EBN: 1

Ploidy: Diploid

Self-compatible: No

Cytoplasm Type: Unknown

Description

Solanum jamesii, sometimes known as the “Four Corners potato,” is a wild potato of the United States and northern Mexico.  It is the only wild species with a distribution primarily in the United States, where it is found mostly in Arizona, Colorado, New Mexico, and Utah, but also reaches slightly into west Texas.

S. jamesii was used for food by native Americans, likely cultivated to some degree, and possibly even improved.  The primary pieces of evidence for its cultivation are (1) that populations are frequently found in close association with sites of previous human habitation and (2) that high levels of genetic diversity in some locations may indicate that plants were collected from other areas (Kinder 2017).  Some people seem to have some rather romantic notions about this species, based upon the number of inquiries that we receive from people who want to find some to grow as food.  Unfortunately, S. jamesii has pretty high levels of glycoalkaloids relative to the domesticated potato.  It would be easy to get sick from eating it.  Apparently, it was traditionally eaten with clay or processed in some fashion and used dried (Moerman 1998) in order to eliminate some of the glycoalkaloids.

S. jamesii tubers are small, reaching about an inch in diameter, but perhaps twice that under cultivation.  Tubers can remain dormant for very long periods.  Bamberg (2010) found that tubers of many collections would store successfully at 41 degrees F (5 C) for eight years and recounted a story from a landowner who observed plants growing on resumption of irrigation after 39 years.  While 39 years seems unlikely, the upper limit for dormancy in S. jamesii remains unknown.

Kinder (2017) reported that wild collected tubers of S. jamesii had twice the protein content of S. tuberosum, along with substantial increases in potassium, calcium, magnesium, and other minerals.  The protein is probably largely a consequence of tuber size.  Smaller tubers have a lower ratio of skin to flesh and most protein is found in and under the skin of the tubers, so small tubers are typically higher in protein.

This species can survive frosts down to 26 degrees F (-3.5 C) (Li 1977).

Condition Level of Resistance Source
Potato Virus A Moderate Webb 1961
Potato Virus X Moderate Webb 1961
Wart Somewhat resistant Machida-Hirano 2015
Potato Leaf Roll Virus Somewhat resistant Machida-Hirano 2015
Colorado Potato Beetle Somewhat resistant Machida-Hirano 2015
Root Knot Nematode Somewhat resistant Machida-Hirano 2015

Cultivation

Solanum jamesii grows in the high desert of the southwest United States and northern Mexico.  It is adapted to dry conditions, with hot days and cold nights.  In the wild, S. jamesii usually sprouts during the rainy season in July and August (Kinder 2017).  In cultivation, with irrigation, it can be started much earlier in the year.

I have found S. jamesii easy to germinate, using the standard conditions for S. tuberosum.  Albino or chlorophyll deficient seedlings seem to be common in S. jamesii.  The albinos will die as seedlings and the variegated types are inferior and not worth keeping.

As is true of most diploid potato species, S. jamesii is an outbreeder.

The USDA potato genebank has observed that germination of some accessions of this species is inhibited by gibberellic acid (Bamberg 1999).

Crosses with S. tuberosum

Livermore (1940) attempted to make reciprocal crosses between tetraploid S. tuberosum and chromosome doubled S. jamesii without success.  This is consistent with what we know of S. jamesii.  It is a diploid species with 1 EBN.  After chromosome doubling, it would behave as a tetraploid with 2EBN.  Because S. tuberosum is tetraploid and 4 EBN, the cross is not compatible even after doubling.

Female Male Berry Set Seed Set Germination Ploidy Source
 S. tuberosum S. jamesii None None     Jackson (1999)
S. jamesii S. tuberosum None None     Jackson (1999)

Crosses with other species

Watanabe (1991) found that 7.8% of varieties of this species produced 2n pollen and Jackson (1999) found 1-18%, which would be effectively tetraploid and 2EBN.

Female Male Berry Set Seed Set Germination Ploidy Source
             

Glykoalkaloid content

Johns (1990) found levels of 115mg/100g and 128mg/100g for two accessions of S. jamesii.  The primary glycoalkaloid was tomatine.  This is about six times the generally recognized safe upper limit for total glycoalkaloids of 20mg/100g.  While S. jamesii can probably be eaten in small quantities without causing distress, it would not be possible to consume it as a staple without finding a way to reduce the glycoalkaloid content.

It is possible that it is overly conservative to assume the same safe dosage for tomatine as for solanine and chaconine.  Green tomatoes, which are a fairly common food, may contain anywhere from 50mg/100g to 500mg/100g of tomatine.  Although it hasn’t been studied in humans, this suggests that we may tolerate tomatine better than the more common potato glycoalkaloids.  On the other hand, the reports that S. jamesii was traditionally eaten with clay cast some doubt on that.  Be careful if you intend to experiment with eating this species.

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