Breeding for Sugar Beet Storage
I’ve had a few discussions around the topic of breeding for storage, with breeders, industry, and farmers alike. The consensus is that, while it’s a nice idea and that it would be possible, it’s not been economical. It’s a nice bonus if a variety stores well, but it’s not the primary aim of any breeding program (that I know about). This is largely a result of there not being a cheap and reliable means of assessing storability.
The work of COBRI and others on mechanical properties has somewhat been based on solving this problem. The thinking is that if a variety is tougher, it will have less damage, less healing to do and less pathogen incursion, and thus not lose as much sucrose during storage. This toughness is usually a result of more cell wall content in the beet. In my view, and while successful research in its own right, it is hard to say that assessment of mechanical properties has proved the answer. Or, at least, a substantially better answer than just breeding for higher sugar content. One of the biggest hurdles to the method is that the relationship between mechanical properties and respiration is not strong. So even if a beet is tough and has little issues with rot, it might still be eating up its own energy reserves at a fast rate.
Then along came a collaboration in Austria. This exciting news first came to our attention at IIRB Congress of February 2020, but has since been published. They have been able to map out a lot of the genes that are up- or down-regulated in beets that store well. It’s early days, but I’m hopeful. The hope being that having identified which genes are important in storage, the magic employed by breeders can be used to target incorporating said genes into new lines.
Another interesting little side conclusion from this work (that was new to me) is that beets with smaller cell size tend to store better. Smaller cell size has been found to be a predictor of damage and grey rot in apples, and probably of other rots and in other fruits too. This conclusion seems to tie in pretty well with what we see, at least on the surface, with the logic being smaller cells = more cell wall material as a proportion of total = less damage = less loss in storage. I don’t believe this has been tested for beets yet.
First, Silvia Madritsch, who presented the work at IIRB 2020, successfully defended her thesis in February. Congrat Dr. Madritsch.
At the American Society of Sugar Beet Technologists on 3 March, Karen Fugate presented the work of her team in the USDA and elsewhere, that includes some similar work to the AIT work plus some big steps forward. The presentation is behind a pay wall, so I can’t share any of the results, but it will undoubtedly be soon published. A few things struck me from this presentation:
- little in known about sugar beet metabolic regulation. This is what I took from the work of Fugate’s team when I wrote my Introduction Paper, but it is great to hear it from the expert.
- Bidirectional Sugar Transporters (BSTs) move sucrose to and from the cellular stores (vacuoles) and seem to be what is most impacted in terms of gene expression during storage. N3 was the BST of interest and it was something like 30 000 times as ‘expressed’ after 1440 degree days.
- Little evidence of sucrose degrading enzyme gene expression change, with the exception of a vacuolar acid invertase (but that took 1440 degree days…)
- This work suggests respiration is sugar beet roots is probably controlled by the glycolitic pathway (which is the way the work of Fugate et al is already leaning).
- Finally, Larry Campbell breed two lines based purely on their respiration rates (one high, one low). How good!
So, in summary, the breakthrough that will lead to the breeding for storage revolution is a big step closer.