|Common Name(s)||Ahuara papa, Papa ra, Para papa, Papa de zorro|
|Synonyms||S. arnezii, S. bitteri, S. boergeri, S. calvescens, S. emmeae, S. garciae, S. gibberulosum, S. guaraniticum, S. horovitzii, S. jujuyense, S. knappei, S. laplaticum, S. muelleri, S. parodi, S. saltense, S. schickii, S. subtilius, S. yungasense|
|Ploidy||Diploid (2x), less commonly triploid (3x)|
|Self-compatible||No (some exceptions)|
|Cytoplasm Type||W (Hosaka 2009)|
|Citation ||Bitter: Repert. Spec. Nov. Regni Veg. 11: 18. 1912.|
Solanum chacoense (chacoense means “from Chaco,” and probably refers to Chaco, Argentina but there are a number of places named Chaco in the range of this plant) is a very diverse and widely spread species, ranging from Peru south and east into Bolivia, Argentina, Paraguay, Uruguay, and Brazil, where it grows from sea level up to about 6500 feet (2000 m). Plants are typically between 1 and 2 feet tall, with narrow strongly pointed leaves. It grows in a wide variety of habitats and is common weed of cultivated ground as well. Tubers are typically small, mostly less than an inch, occasionally reaching as much as three inches. They are usually white to tan in color, less commonly blue, usually with prominent lenticels.
Although most South American wild potato species are short day tuberizers, some accessions of S. chacoense are able to tuberize under long days.
Subramanian (2017) found that at least some accessions of this species have unusually low calcium and potassium content and unusually high dry matter.
Bethke (2017) scored wild potato species as a composite of seven resistance studies and S. chacoense ranked in third place.
Some accessions of S. chacoense deter the feeding of Colorado potato beetle and many other insects due to leptines (acylated glycoalkaloids) in the foliage. Leptines are not common in S. chacoense and so far have not been found at all in other potato species (Sinden 1986). Leptines were not found to accumulate in the tubers even when allowed to green (Sinden 1986b). Sinden (1980) found the least damage from Colorado potato beetle in varieties that had forms of commersonine as their primary glucoalkaloids.
|Condition||Type||Level of Resistance||Source|
|Aphids||Invertebrate||Somewhat resistant||Adams 1946|
|Bacterial ring rot||Bacterium||Somewhat resistant||Ross 1958|
|Bacterial Wilt||Bacterium||Somewhat resistant||Machida-Hirano 2015|
|Colorado Potato Beetle||Invertebrate||Somewhat resistant||Stelzner 1943, Schaper 1953, Torka 1943, Machida-Hirano 2015|
|Drought||Abiotic||Somewhat resistant||Machida-Hirano 2015|
|Early Blight||Fungus||Somewhat resistant||Jansky 2008|
|Frost||Abiotic||Somewhat resistant||Machida-Hirano 2015|
|Golden nematode (G. rostochiensis)||Invertebrate||Somewhat resistant||Castelli 2003|
|Heat||Abiotic||Somewhat resistant||Machida-Hirano 2015|
|Late Blight||Fungus||Not resistant||Gonzales 2002|
|Late Blight||Fungus||Somewhat resistant||Machida-Hirano 2015, Bachmann-Pfabe 2019|
|Potato Cyst Nematode (G. pallida)||Invertebrate||Somewhat resistant||Castelli 2003|
|Potato Cyst Nematode (G. pallida)||Invertebrate||Not resistant||Bachmann-Pfabe 2019|
|Potato leaf miner||Invertebrate||Somewhat resistant||Ochoa 1990|
|Potato leafhopper||Invertebrate||Somewhat resistant||Sleesman 1940|
|Potato Leafroll Virus||Virus||Somewhat resistant||Ross 1950, Ross 1958, Ochoa 1990|
|Potato tuber moth||Invertebrate||Somewhat resistant||Ochoa 1990|
|Potato Virus X||Virus||Somewhat resistant||Lebedeva 1978, Machida-Hirano 2015|
|Potato Virus Y||Virus||Somewhat resistant, Resistant||Ross 1950, Ross 1958, Ochoa 1990, Cai 2011, Machida-Hirano 2015|
|Potato Virus Y, C Strain||Virus||Resistant||Takacs 1999 (as S. arnezii)|
|Root Knot Nematode||Invertebrate||Somewhat resistant||Machida-Hirano 2015|
|Scab||Bacterium||Somewhat resistant||Machida-Hirano 2015|
|Soft Rot / Blackleg||Bacterium||Somewhat resistant||Chung 2011, Machida-Hirano 2015|
|Verticillium wilt||Fungus||Somewhat resistant||Lynch 1997|
|Wart||Fungus||Somewhat resistant||Machida-Hirano 2015, Ross 1958|
The glycoalkaloid composition of S. chacoense varies considerably between accessions. Sinden (1980), found six different glycoalkaloid profiles for this species: commersonine; solanine; dyhydrocommersonine; leptines and commersonine; solanine and chaconine; dihydrosolanine and dihydrochaconine; and leptines with dihydrosolanine and dihydrochaconine. Sinden (1986b) found TGA levels ranging from 134 to 279 mg / 100 g across three clones of S. chacoense.
Bamberg (2017) found a 306% increase in seed set in this species with supplemental applications of liquid fertilizer at four and seven weeks after potting.
Towill (1983) found that seeds of this species stored at 1 to 3 degrees C germinated at 90% after 25 years.
I recommend isolating S. chacoense from domesticated diploids by at least 40 feet if you will be saving seed. This species appears to be a very effective pollinator and progeny of crosses with diploid S. tuberosum are mostly bitter.
S. chacoense has shown a significant ability to naturalize and become weedy in foreign environments (Simon 2010). Care should be taken to prevent this species from escaping and growing unmanageably, a precaution that should be taken with all wild potato species until you have experience with them. There is a lot of rainfall in most of its native range, but it appears to tolerate drought very well.
Trapero-Mozos (2018) determined that this species will tolerate a temperature of 40 C even without prior acclimatization to warm temperatures.
Lynch (1997) identified a dominant, single gene source of Verticillium resistance in some accessions of S. chacoense. This could likely be crossed into S. tuberosum without too much difficulty.
Ochoa (1990) reported that the pollen fertility of triploid S. chacoense (as S. yungasense) was 45-50%, a surprisingly high value for a triploid.
Crosses with S. tuberosum
|Female||Male||Berry Set ||Seed Set||Germ||Ploidy||Source|
|S. chacoense||S. tuberosum 2x||Yes||Yes||Ochoa (1990)|
|S. chacoense||S. tuberosum 4x||None||None||Jackson (1999)|
|S. tuberosum 2x||S. chacoense||Yes||Yes||Ochoa (1990)|
|S. tuberosum 4x||S. chacoense||Low||Low||Jackson (1999)|
Crosses with other species
Jackson (1999) found 2-11% 2n pollen for this species.
|Female||Male||Berry Set ||Seed Set||Germ||Ploidy||Source|
|S. chacoense||S. berthaultii||High||High||Ochoa (1990)|
|S. chacoense||S. brevicaule (as S. vidaurrei)||Yes||Yes||Ochoa (1990)|
M6 is an improved variety of S. chacoense, introduced in 2014. It is homozygous for the Sli gene, able to self-pollinate and produce vigorous progeny, and is a day neutral tuberizer. M6 can be used in breeding with domesticated diploids to reliably introduce self-compatibility, since the Sli gene is dominant.