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Solanum cardiophyllum

Common Name(s)Cimatli, heartleaf horsenettle, heartleaf nightshade
Above ground plant of the wild potato species Solanum cardiophyllum
Solanum cardiophyllum plant
Codecph
SynonymsS. lanciforme, S. coyoacanum
Clade1
SeriesPinnatisecta
PloidyDiploid (2x), Triploid (3x), Tetraploid (4x)
EBN1
Tuberization PhotoperiodDay neutral
Self-compatibleNo (Kuhl 2002)
Genome
BB
Cytoplasm TypeW (Hosaka 2014)
Citation
Lindley: J. Hort. Soc. London 3: 70, fig. pg. 71. 1848.

Description

Solanum cardiophyllum distribution Map note

Solanum cardiophyllum (cardiophyllum, meaning “heart leaf”) 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.  Despite the name, the plant doesn’t really have heart shaped leaves, although the seedlings sometimes do.  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.

Resistances

Vega (1995) found that this species is less frost tolerant than domesticated potato.

ConditionTypeLevel of ResistanceSource
AphidsInvertebrateSomewhat resistantMachida-Hirano 2015
AphidsInvertebrateResistantAlvarez 2006
Colorado Potato BeetleInvertebrateSomewhat resistantMachida-Hirano 2015
Early BlightFungusResistantPrasad 1980
Late BlightFungusResistantMachida-Hirano 2015
Potato Cyst NematodeInvertebrateSomewhat resistantMachida-Hirano 2015
Potato Virus YVirusSomewhat resistantChung 2011, Machida-Hirano 2015
Root Knot NematodeInvertebrateSomewhat resistantMachida-Hirano 2015
WartFungusSomewhat resistantMachida-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

Solanum cardiophyllum plant
Solanum cardiophyllum plant
Above ground plant of the wild potato species Solanum cardiophyllum
Solanum cardiophyllum plant
Above ground plant of the wild potato species Solanum cardiophyllum
Solanum cardiophyllum plant
Flower of the wild potato species Solanum cardiophyllum
Solanum cardiophyllum flower
    
    

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

FemaleMaleBerry Set
Seed SetGermPloidySource
S. cardiophyllumS. tuberosum 4xNoneNone  Jackson (1999)
S. tuberosum 4xS. cardiophyllumMinimalNone  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.

FemaleMaleBerry Set
Seed SetGermPloidySource
       

References

Solanum cardiophyllum at Solanaceae Source

Solanum cardiophyllum at GRIN Taxonomy

Solanum cardiophyllum at CIP

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