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[Ishmael Fleishman]

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Edited August 21, 2024 by Ishmael Fleishman

[Fathom]

A seedling population from a single fruit can have multiple phenotypes and genotypes present.

 

The ovary of San Pedro cacti has hundreds to thousands of eggs and the flowers produce millions if not billions of pollen gametes. This means that the seeds in a single fruit can have more than one parent, which is one of the ways that a single population of seeds from a single fruit can have significant variation. 

 

However, cacti are also, generally speaking, diploid and have 11 chromosomes as their base number. So for the most part any San Pedro seedling has 22 chromosomes.

This is also true of the parent, which forms gametes like eggs and pollen (sperm) that only have 11 chromosomes. This means that in heterozygous individuals, which is typically the case with horticultural San Pedro cacti, a single parent can contribute two distinct alleles for each chromosome. Say that the parent cactus is the common US clone PC, this hybrid plant carries alleles for short and long spines and when used as a parent the offspring of the plant are never uniform, instead they vary, regardless of what the other parent is.

 

However in some unusual cases, like with T. scopulicolus and T. bridgesii it is possible to have cactus seedling populations that are more uniform and breed true. However anyone who has planted a couple thousand  seeds will tell you that the phenotype still varies to a degree even with populations of pure bred material. In fact, it is unusual to have strongly uniform San Pedro seedling populations. 

 

There are multiple ways for cacti, especially San Pedro cacti, to have considerable variation in their offspring.

 

Some of this is more remarkable and profound than other cases. In the case of intergeneric and interspecific hybrids involving these cacti, like Zelly's Zelly cross, white the majority of the population are largely uniform in some ways there are outliers in the populations. Take the Zelly cross, most of the specimens from this look like small San Pedro cacti with shorter statures, though flower color varies considerably. However in that population another form was produced which is taller, thicker and has a white flower, more like San Pedro. 

 

Because variation is extremely common with these cacti it allows for selections to be made, like picking out, naming and propagating a clone, which can be considered superior to their siblings in terms of whatever trait was selected for. This type of selection is integral to the history and tradition of San Pedro cacti as well as to the modern breeding projects involving it today.

 

Edited August 19, 2024 by 16777216