In my AP Biology class, we were discussing polyploidy, specifically, its deleterious nature in mammals and its prevalence in plants. We also learned that commercial crops, especially fruit, are often selectively bred for high magnitudes of ploidy.

Fascinated, I googled the subject and ended up reviewing the Wikipedia article to get a little more background info, where I read this:

Polytene chromosomes of plants and fruit flies can be 1024-ploid.[44][45] Ploidy of systems such as the salivary gland, elaiosome, endosperm, and trophoblast can exceed this, up to 1048576-ploid in the silk glands of the commercial silkworm Bombyx mori.[20]

From this, I have three questions. The first is, is there an upper limit to ploidy that can occur in nature? I understand that polyploids can "lose" ploidy by haploidisation, but is this as common as increases in ploidy? I believe that the answer to this would imply the answer to my first question, however, I could not find much literature in the way of this area.

My second question is, is there an upper limit to synthetically induced polyploidy? Is the Bombyx mori's ploidy arbitrary, or is it at the max that technology can produce? Can it's ploidy be expanded further?

Lastly, does arbitrarily high ploidy serve any purpose in agriculture or science? Is there a threshold where utility is no longer maximized?

Thank you in advance.


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