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 cardiophyllum

Common Name(s): Cimatli, heartleaf horsenettle, heartleaf nightshade

Synonyms: S. lanciforme, S. coyoacanum

Series: Bulbocastana

EBN: 1

Ploidy: Diploid, Triploid, Tetraploid

Segregation: Disomic

Self-compatible: Sometimes

Cytoplasm Type: W (Hosaka 2014)

Description

Solanum cardiophyllum is a North American species, found primarily in Mexico.  It is also present in some parts of the SW United States, but was probably introduced.  It is commonly known as cimatli (along with S. ehrenbergii), heartleaf horsenettle, or heartleaf nightshade.  This is one of the few wild potato species that was commonly used as food.  The Aztec and the Chichimeca ate S. cardiophyllum and the practice continues in some parts of Mexico today (Johns 1990).  In fact, there was at least one farm that was growing S. cardiophyllum, S. ehrenbergii, and S. stoloniferum for market in Jalisco as recently as 2010 (Villa Vazquez 2010).

Plants can reach a little over two feet in height, although many are much smaller in the wild.  Although S. cardiophyllum has small tubers, reaching about an inch in diameter, they compensate with a rare trait in wild potatoes: palatability.  In fact, the flavor is not easily distinguishable from domesticated potatoes.  The level of glykoalkaloids in some accessions of this species is sometimes very low, about 2 mg/100 g (Johns 1990).  That level is lower even than most domesticated varieties, although other accessions have been found to have much high and unsafe levels of glycoalkaloids (see below).  Given the good edible qualities of at least some accessions, it is something of a mystery why the native Mexicans who domesticated so many other species did not improve S. cardiophyllum.  Of course, it is possible that they did and we just don’t know about it.  Current research is underway to determine if S. cardiophyllum might have been used by the Anasazi to improve the tuber size of S. jamesii (J. Bamberg, personal communication, 2018).

Although crossing wild potatoes to S. tuberosum is usually the goal, I think that amateur breeders might find it rewarding to work on the improvement of S. cardiophyllum itself.  Even though the tubers are small, the species has many valuable traits and it might be possible to work on them more productively simply by breeding better varieties of S. cardiophyllum.

Condition Level of Resistance Source
Late Blight Resistant Machida-Hirano 2015
 Wart Somewhat resistant Machida-Hirano 2015
 Potato Virus Y Somewhat resistant Chung 2011, Machida-Hirano 2015
 Colorado Potato Beetle Somewhat resistant Machida-Hirano 2015
 Aphids Somewhat resistant Machida-Hirano 2015
 Potato Cyst Nematode Somewhat resistant Machida-Hirano 2015
 Root Knot Nematode Somewhat resistant Machida-Hirano 2015

Glykoalkaloid content

According to Johns (1990), S. cardiophyllum did not contain measurable amounts of solanine or chaconine, only a small amount of a glycoalkaloid tentatively identified as demissine.  (I am not citing specific amounts, because at least some of the accessions of S. cardiophyllum included have since be reclassified as S. ehrenbergii and vice versa.)  Based on this report, S. cardiophyllum might serve a more digestible substitute for those who have difficulties with the common potato glycoalkaloids.

On the other hand, Sotelo (1998) found much higher and clearly unsafe TGA levels of 138.8 mg/100 g and 137.5 mg/100 g (solanine and chaconine combined and recalculated from dry to wet weight).  S. cardiophyllum accessions will need to be carefully evaluated for safety, although any with levels as high as these should be terribly bitter and inedible.

Images

Cultivation

I have found this species about as easy to germinate as S. tuberosum under the same conditions.

S. cardiophyllum is native to highland areas in Mexico.  It is adapted to somewhat warmer and drier conditions than the Andean wild potatoes.

According to Villa Vasquez (2011), where S. cardiophyllum is farmed in Mexico, it is planted in November and June in tunnels or in open fields in July.  The tubers are sown only 2.5 inches (5 cm) apart in rows about 20 inches (50 cm) apart.  The average temperature during this period is about 72 degrees (23 C), reaching a maximum of about 90 (32 C).  This is significantly earlier than the plants grow naturally and requires irrigation.  The plants are forced to tuberize by withholding water.  Harvest is about 3.5 pounds per square yard.

The flowering period of this species is relatively short – about 4 to 6 weeks.

This species is listed as a noxious weed in California.

Breeding

While my own selections top out at about an inch in diameter, the USDA Potato Introduction Station has made some selections with tubers as long as 2 to 3 inches.  This bodes well for cultivar development in this species.

Diploids of this species are sometimes self-compatible (Estrada-Luna 2002).  Tetraploids are generally not self-compatible due to male sterility.

Crosses with S. tuberosum

Female Male Berry Set Seed Set Germination Ploidy Source
S. tuberosum S. cardiophyllum Minimal None     Jackson (1999)
S. cardiophyllum 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 1-16%, which would be effectively tetraploid and 2EBN.

Female Male Berry Set Seed Set Germination Ploidy Source
             

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