Diploid, Triploid, Tetraploid..

[Voodoo]

I am looking for a bit of clarification on hop breeding - whats the difference (and pros / cons) between diploids / triploids / tetraploids other than the fact that tris have three sets of chromosomes and tetras have four?

Here's the extent of my limited knowledge: all "landrace" hops are diploid and several older varieties have lost their vigor from years of propagation. Diploid hops that are deemed worthy by breeders are then sprayed with colchicine to split the chromosomes (tetraploids) but aren't viable for propagation. (Why not?) Tetraploids are then crossed to diploids to get more-or-less sterile triploids so commercial growers can run fields without worry of seed / stronger variants of their diploid counterparts.

More questions: Can you cross tetraploids to one another? Are there too many expressions to be worthwhile? Why are breeders moving away from diploid crosses? Wouldn't hybrid vigor be restored in a diploid cross? Has anyone used ethylene / hormone regulating agents (colloidal silver / STS) that change the females to "males" which can then be used to create feminized hop lines?

 

[PapaBearJay]

@Voodoo

Yes, the original landrace varieties are diploid but they also have tetraploid counterparts. These tetraploids were induced using colchicine, as you mention, but they are only used in breeding. Additionally it's not due to the propagation per se, it's likely more a result of slight mutations that occur during mitotic (cell division) events coupled with viruses, fungi, and other diseases that reduce the overall vigor of the plant. Since continued propagation can result in accumulation of a number of these, vigor does tend to decline over time which is why there is the National Clean Plant Network - Northwest Center that provides propagation material that has been indexed for specific pathogens.

The use of colchicine doesn't "split" the chromosomes, it actually does the opposite. It inhibits certain steps of mitosis that prevents spindle fibers in forming and dividing the chromosomes equally into the two new cells. This results in one of those two new cells having no chromosomes and the other having a doubled (tetraploid) amount. The issue here is making sure that the tetraploid cell line actually survives and can be propagated from. It's not that they're not viable for propagation, but polyploidy itself can actually reduce vigor. Think of it this way, in the diploid state you only have to worry about replicating two sets right? That takes enough energy of it's own, but think about if you had to do that with four sets, six sets, eight sets of chromosomes?! That's two, three, or four times the energy needed to replicate yourself!

Yes, in some areas of the world breeding programs use tetraploids crossed to diploids to generate triploid varieties. In most instances, triploids are sterile (theoretically speaking) but nature will find a way, I can assure you of that. Tetraploids can be crossed with each other, but you first have to generate them and have both male and female plants (remember that each plant is an individual sex, not both).

Clarify what you mean by expressions.

Breeders are not moving away from diploid crosses, polyploidy has been around for the past 60-70 years in hop breeding, and "official" hop breeding has only been around for the past 108 years. Hybrid vigor has a limited amount to do with the ploidy level (ploidy will impact this, albeit only slightly) and is more related to how related two individuals are with each other. Yes, people have used plant hormones and other agents to induce sex changes in hops, there's a patent on some of what you speak. Unfortunately, I don't feel the need to involve lawyers in what I do during my free time, so I try to limit my law-breaking to jaywalking.

 

[Voodoo]

Thank you PapaBearJay for the very informative response! I appreciate you taking the time to educate a rookie hop grower.

I was completely unaware of the fact that the use of STS in hops was patented. I was not advocating anything illegal or considering it, but I had heard of its use with other plants and thought it made sense to cross plants to themselves to get the result you wanted by limiting the gene pool.

 

[nagmay]

There are patents on the induction of sex expression in hops? I better watch my back http://gabriel.nagmay.com/2014/02/hop-breeding/

My plan for this year was actually to work on developing some polyploid breeding stock - but everything sprouted before I could get the chance to do a colchicine soak. Oh, well. Something to look forward to for next year.

 

[B-Hoppy]

I was always under the impression that the colchicine was applied to areas of the plant where there was a bunch of active cell division occurring like the growing tips?

 

[m00ps]

triploid, diploid, haploid...guh, does everything with you people have to be about sex???

 

[nagmay]

I was always under the impression that the colchicine was applied to areas of the plant where there was a bunch of active cell division occurring like the growing tips?

When I've used it in the past - on orchids - it was always a seed treatment prior to germination. The thought being that you are starting with a single cell. If the treatment works (and it survives), all the following cells in the plant will have a consistent number of chromosomes.

I suspect that it could be used on growing tips to induce a "bud sport", but you are dealing with a lot more cells - which would complicate things.

 

[B-Hoppy]

I guess the procedure is different for different plants. I'd seen Doc. Haunold cited in a few articles and found this one: https://www.researchgate.net/public...s_effect_on_morphological_and_chemical_traits. Cool stuff but would take more time than I can afford. Have at it!

 

[nagmay]

Very cool. Thanks for the link.

 

[Voodoo]

Nagmay - very interesting link! So a naturally stressed Magnum produced pollen and from what I gather, a rather low instance of hermaphroditism in the resulting plants.

I'm assuming that the Magnum x Cascade is about the standard bell curve of genetic traits between mom and dad. Anything unexpected show up from the cross or are they all semi cascade, semi magnum?

 

[nagmay]

So a naturally stressed Magnum produced pollen and from what I gather, a rather low instance of hermaphroditism in the resulting plants.

Yes.

I tried for several years and had success inducing pollen in female plants using stress and colloidal silver. However, no viable seeds were produced from the pollen. The one that finally worked was a naturally stressed Magnum - though, I have no doubt that colloidal silver could produce results with a large enough population.

I'm assuming that the Magnum x Cascade is about the standard bell curve of genetic traits between mom and dad.

Not really.

The offspring were mix and match randomization of phenotypes - no two were the same. I am now running 3 yards with several hundred crosses and each seems to be a "unique snowflake". You can see some of the original crosses here: http://gabriel.nagmay.com/2014/09/hop-breeding-2014-results/

Unlike other plants that have been backcrossed to stabilize the phenotypes, the hops grown from seed can be significantly different from their parents. Perhaps this is why I find myself planting larger and larger amounts of seed each year

 

[nagmay]

To clarify, by "unique" I don't mean "completely random". There do tend to be some trends that are based on the parentage. This is one of the reasons why I continue to be excited about crossing using known genetics.

Most of the Chinook offspring, for instance, do seem to have the signature hook on the end of the bracts.

I also have another male that I developed who produces produces offspring with consistently large, abundant cones - regardless of the mother's traits.