Tuber Stock: Health and Prosperity

Krista

I read about the deterioration of stock, and the need to refresh and bring in new at times, but I don't know what the causes are. Are there cultural factors that contribute to the breakdown of genetics? Are some factors simply inevitable? Can we lower the odds of this occurring by ensuring excellent growing conditions? The question mostly is: "what can we do to prevent the breakdown and what cannot be controlled?"

Bessie

Krista There are complex factors that control how long an organism will live, such as good or bad genetics( plant 'hybrid vigor'), favorable vs. an unfavorable environment, and diseases or pests the organism may be exposed to. There is much that is unknown about genetic material breakdown, therefore there are no "easy answers" on how to prevent genetic breakdown, that I know of. Good plant culture, that facilitates healthy plant growth is the key to optimum plant longevity, and fighting off diseases and pests, in my opinion.

Krista

Bessie Thank you, yes all of the unknowns are easy to get lost in! I appreciate your opinion so much, I am with you, I want to do what I can to prevent disease, deter pests and facilitate healthy plants too!

Teddahlia Whoa wild. And while discouraging for someone like me without the space to benefit from power in numbers, this is really helpful. 1-5% is a high number to lose each season, it's a wonder that varieties can even exist for as long as they do. I am still learning everything, so you're right, crappy stock is still something I'll need to continue to be better at identifying. Pot tubers: I understand are planted to ensure backup stock. Can providing undesirable growing conditions (not enough space, water or light) expedite genetic damage over time?

Teddahlia

Plants are subject to radiation from cosmic rays that cause mutations. They are subject to genetic instability where some of the genes are not well constructed and do not duplicate well. If you are growing 100 plants of a nice variety, how many of them will be infected with genetic damage each year? My guess is that 1-5% of them may suffer in some way. If the grower culls the poor growing plants, perhap half of the them will be gone but there will always be some with damage. If the grower is careful and only sells the the most vigorous and healthy plants and always culls the poor ones, he can grow the stock for decades. In your garden, if a plant is compromised, you may not have a healthy one to keep and most small growers keep the crappy stock and and may not even know it is crappy.

Emilyp

Teddahlia . If the grower is careful and only sells the the most vigorous and healthy plants and always culls the poor ones, he can grow the stock for decades.

It seems to me like this is the method used at Halls of Heddon. They grow 100's of each variety, cull the undesirable plants, then use the best to make next year's cuttings and pot tubers. I like it.

Teddahlia

"...expedite genetic damage over time." Simple answer is no. Genetic damage is caused by radiation or chemicals not poor growing conditions. Small growers including myself often do not grow enough stock to cull and end up saving crappy stock. A big time show grower I know never gives away his best stock although his second best stock is better than yours or mine.

Bessie

Teddahlia my "gut" tells me that healthy growing conditions very well could contribute to resistance to genetic damage. There is much going on at the cellular level, lots of enzymes, Co-factors, nutritional levels(NPK and micronutrients) during the cell division, essential amino acids, etc. I was reading a paper(that was somewhat over my head) that went into detail in how the genetic damage takes place at the base pairs ( pieces of DNA) level during cell division. It just makes sense (to me) that a deficiency of a critical component in the cell chemistry could make the cell division go haywire. In simple terms, genetic damage is cell division making a "mistake". With all this said, I reserve the right to be wrong. My daughter asked me, "do I have a source'... Found this article on Genetics and Nutrition [link](Genetics and nutrition - PubMed
https://pubmed.ncbi.nlm.nih.gov/14512029/#:~:text=Nutrients%20can%20induce%20gene%20expression,nutrients%20to%20interact%20with%20them.)

Teddahlia

You can be 100% correct about this issue but the percentage of plants that suffer genetic damage is very low and if you are correct the odds go from "almost never get a negative sport" to 10% more than almost never which for most people is still almost never. Pot tubers are an excellent way to keep over stock for many years. Most of the reasons for using pot tubers are not preserving the good stock but are insurance that you will still have ANY stock as you can lose all of it in your garden. I have had only my pot tubers of numerous varieties as the garden plants failed. And as far as how "skinny" you grow your pot tubers, there is no law against giving them a little bit of fertilizer to make them a bigger plant. Percentage wise, most people who grow pot tubers have them down on or in the ground where they get more fertilizer. I find it more convenient to grow on a mesh table in part shade.

Krista

This is great! Basically, we just need to be prepared to dig and find zero tubers. Our already developed pot tubers created early spring, in sterile environment, ensures plants for next year. Shame on me for getting to dig-season without a back up. 😝 And I’m just going to have to be prepared to lose varieties since I simply don’t grow the volume required to insure stock quality. I can definitely wrap my head around this. Thank you, all, for helping me get here.

Ailhad

Are dahlia tuber growers familiar with the production requirements for potato seed tubers? The problem of seed tuber degeneration in potatoes is fairly well studied and the main reason are a build up of pathogens and pests. That's why there are specialized and certified potato seed tuber growers. Random somatic mutations seem to be a lesser problem. I would bet, degeneration of dahlia stock is also largely due to viruses and diseases.
Couldn't find a simple summary of potato seed tuber production but this reference discusses some interesting aspects, and is open access and not too hard to read. ☺
https://doi.org/10.1111/ppa.12439

PNWGal

Ailhad Thanks for the link & the perspective. There has been lots of talk about establishing a source for clean dahlia stock, but we are still a long way from that, at least as far as virus is concerned. I found it interesting that the article refers to these potato seed tubers as "certified to have pathogen and pest incidence below established thresholds". No claims that they are completely pest and disease-free.

Teddahlia

Seed potatoes are the created by taking meristem cuttings and then lots of testing to be sure the plants are clear of pathogens. The resulting plants are sold to seed producers to grow the certified seed potatoes that are used to plant the crop. The same methods could be used for dahlias. I have been saying for years that the ADS should either preserve good stock when it is introduced by nitrogen freezing or set a up program to periodically clean up some popular varieties and distribute them.

Ailhad

Teddahlia That sounds interesting. Especially, since prices for dahlias continue to rise, it might actually become economically feasible to produce and sell certified dahlia seed tubers.