Question about a cycad's "hybrid vigor"

[Ventri]

It's well known that hybrids may sometimes be recognized as having "hybrid vigor." Does such a claim hold true for cycad hybrids?
Hybrid vigor seems to be exclusively used to refer to angiosperm hybrids, or plants that are commonly polyploid. ( the heritable condition of possessing more than two complete sets of chromosomes)

To my knowledge, polyploidy is rare in non conifer gymnosperms, and entirely absent in cycads. If that is the case, how is it possible for cycads to have true hybrid vigor?
Has anyone here with a cycad hybrid ever done a chromosome test on it? I can't find any information online, and am rather interested.

[Merlyn]

I'm not aware of any genetic research on cycad hybrids, but I honestly haven't looked for it either.  As far as growth rate goes, hybrids seem to have two advantages here:

• The cold and frost hardiness seems to be at least as good as the tougher parent, perhaps better.  For example, an 8" caudex Gratus and a couple of 3-10" caudex Laurentianus were defoliated this winter (and last winter) in my backyard, but similarly-sited Gratus x Laurentianus were only slightly damaged.  Likewise a Gratus x Whitelockii and Sclavoi x Ituriensis hybrids were undamaged while the pure species nearby were defoliated or significantly burned.  And that's with the hybrids being smaller plants and more exposed to frost.  I can't make the same assessment on Cycas here, because the pure species and hybrids I have (Rev x Deb, Rev x Diannanensis, Panz x Deb, etc) are all super hardy to my minimum temps (24-26F) with frost.
• The water tolerance seems to be inherited from the most tolerant parent too.  E. Aemulans x Trispinosus, Gratus x Tri, and a couple of others seem find in the ground without supplemental watering.  Horridus and Arenarius hybrids do ok in well-draining spots.  Pure Trispinosus, Horridus, and Arenarius barely make it through the summer in the ground, and die after the first winter.

Any "hybrid vigor" with these I could probably attribute to less winter damage and better water tolerance.  My Gratus and Laurentianus might push out a new flush by May...and the Gratus x Laurentianus is shooting up a new frond already!

[Manalto]

It's my understanding that hybrid vigor (heterosis) means a hybrid whose qualities are superior to both parents, and not merely a combination of adaptive traits inherited from them. This certainly can be an advantage, but (please correct me if I'm wrong) does not qualify as hybrid vigor.

Edited February 25, 2023 by Manalto

[Merlyn]

1 hour ago, Manalto said:

It's my understanding that hybrid vigor (heterosis) means a hybrid whose qualities are superior to both parents, and not merely a combination of adaptive traits inherited from them. This certainly can be an advantage, but (please correct me if I'm wrong) does not qualify as hybrid vigor.

In the above examples the cold and frost hardiness is definitely better than either parent...especially in the case of Gratus x Laurentianus.  The other hybrids are *likely* tougher than either parent, but it's not dramatic enough (yet) to be sure. 

For water tolerance I think it's less clear.  Trispinosus, Arenarius, and Horridus do ok in pots here with super-draining soil (mostly inorganic), and don't even last a year in the ground before rotting.  The "big green" half of the hybrid (Aemulans, Altensteinii, etc) does fine anywhere in my yard in the ground.  The hybrids are "better than Tri/Arenarius/Horridus" but it's not clear if they are as good as the "big green" half, worse (as in an intermediate of both parents) or better than the "big green" half.  I suspect it's probably an intermediate, i.e. not superior to either parent.

[amh]

Cycads are not of economic importance, so there is a lot less funding for any research, including genetics. Polyploidism and hybrid vigor are not synonymous terms. Allopolyploidy in fruits, flowers, tubers and grains is of economic importance, and therefore, will be heavily researched and common to the general public. From my anecdotal observations, I would say that cycas hybrids do show "hybrid vigor", in that the growth rate is accelerated.