Author Topic: Cactus Chromosome Numbers and Self-Incompatibility  (Read 903 times)

Andrew Barney

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Cactus Chromosome Numbers and Self-Incompatibility
« on: 2018-11-17, 07:49:42 PM »
I have a growing interest in growing Cacti and potentially breeding. With a particular interest in species or clades that could survive and thrive outdoors in my climate, however i'm open to cultivating a few indoors or in greenhouses too.

But in order to dive into what crosses might be compatible i would think knowing the ploidy count or chromosome numbers would help tremendously. In addition knowing which species are self-incompatible would help to know how to get them to fruit properly. If anyone knows of any resources or websites that list this information in an easy to access and understand format please let me know. Otherwise we can keep updating this thread with such information. This is the brief information i have compiled thus far.

Opuntia fragilis = hexaploid
O. macrorhiza = tetraploid
Opuntia humifusa Raf. s.l. = both diploids and tetraploids. (although diploid individuals have been discovered only in the southern portion of the range of the species and only tetraploids have been found in northern populations studied so far.)
O. polyacantha Haw. var. arenaria = diploid
O. polyacantha Haw. var. polyacantha = diploid

Echinopsis chamaecereus [formerly Chamaecereus silvestrii] is a diploid (2n = 22).
Interestingly, all E. chamaecereus plants in cultivation apparently have originated from vegetative propagation of one SI clone (Huxley et al. 1992; R. Kiesling personal communication).

The Cactaceae, a family of about 98 genera and 1500 species of succulent perennials, exhibits SI in all three of its subfamilies
(Pereskioideae, Opuntioideae, and Cactoideae) and at least 28 of its 98 genera (Boyle 1997).

Cactoideae is divided into nine tribes, eight of which contain SI species.
These studies show that SI is widespread in the Cactaceae.

Opuntia fragilis is the most cold tolerant and most northern of all cacti.
All twelve populations of O. fragilis analyzed were hexaploid.

Populations of O. humifusa s.l. and O. macrorhiza s.l. were all tetraploid, indicating that the northeastern-most range of those taxa is occupied by polyploid derivatives of their southern diploid relatives.

The O. polyacantha complex is most species rich in the southwestern United States, where the members of the group are thought to have originated (Pinkava 2002).

Diploid members of the complex (e.g., O. polyacantha Haw. var. arenaria and O. polyacantha Haw. var. polyacantha) are restricted to northern Chihuahua, Mexico, adjacent southwestern Texas, and the southern fourth of New Mexico.

While polyploid members of the clade are found mostly to
the north of those diploid populations
, as far north as
Canada for tetraploid O. polyacantha and hexaploid O.
(Bowden 1945; Parfitt 1991; Pinkava 2002).


  • Physiology and genetics of self-incompatibility
    in Echinopsis chamaecereus (Cactaceae)

    Chromosome Counts of Opuntia (Cactaceae), Prickly Pear Cacti, in The Midwestern United States and Environmental Factors Restricting the Distribution of Opuntia Fragilis
« Last Edit: 2018-11-17, 07:51:50 PM by Andrew Barney »

Joseph Lofthouse

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Re: Cactus Chromosome Numbers and Self-Incompatibility
« Reply #1 on: 2018-11-17, 08:46:45 PM »
I grow one clone each of O polyacantha, and O humifusa. They seem to be self-compatible.


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Re: Cactus Chromosome Numbers and Self-Incompatibility
« Reply #2 on: 2018-11-18, 03:49:06 AM »
The Tropicos web site might be useful if you’re after chromosome numbers:
Mildly acidic clay loam over clay and ironstone; temperate climate modified by altitude (1000m); avg rainfall 780mm; usually wet summers and dry winters.