Ideas on Breeding Micro-Currant Tomatoes

[KaguyaCloud]

I've obtained a copy of "Genetics, Genomics, and Breeding of Tomato" by Barbara E. Liedl and have got some interesting insights on tomato breeding. One of which involves soluble solids content compared to leaf to fruit ratios:

Development of determinate tomato cultivars with concentrated fruit set gives a lower foliage/fruit ratio than in indeterminate cultivars, resulting in limiting carbohydrates that could go into fruit flavor components. Indeterminate lines had higher soluble solids than their isogenic determinate counterparts (Emery and Munger 1970) and high soluble solids selections with large fruit had larger vines with less concentrated fruit set (Rick 1974). Recently, the failed attempts to develop determinate grape tomatoes with the quality of the indeterminates supports this concept.

To shorten the passage: the less leaves per fruit, the less soluble solids per fruit. Here's a passage between soluble solids and size:

Not surprisingly, increases in soluble solids, acidity and pigment concentration due to the cherry QTLs were accompanied by decreases in fruit weight, suggesting that the effects on sugar and acid were secondary to the effect on fruit size. A similar conclusion was reached by Georgelis et al. (2004) who also searched for QTLs for sugar concentration in a large fruit x small cherry cross. The relationship between fruit size and solids concentration has been explained by Ho (1996) and Stevens (1986), relating the differences in fruit size to the size of the parenchyma cells, with the larger cells having a higher water content, thereby diluting the solids.

I would also like to clarify that soluble solids, while an objective measurement of fruit quality, does not include the very small amounts of(but very noticeable) aromatic compounds that may make the fruit taste better. I think it is important to note that distinction.

Micro dwarf tomatoes have an extremely low leaf:fruit ratio even compared to determinates. After 5-9 leaves, they immediately terminate to 2 flower trusses with 5-7 fruits per truss. And to make things worse, their axillary shoots seem to have no vegetative phase, producing a fruit truss after 2-3 leaves grow out. However, this results in a plant with a very large harvest index compared to regular tomatoes. And based off of personal observation, they yield more tomatoes per unit volume of space they take up.

There's been quite a few projects around multiple forums on growing large beefsteak micro-dwarf tomatoes. So, what if we go the opposite direction and breed micros with even smaller, but potentially much tastier fruit? Or maybe go into the realm of larger indeterminate micro lines? I don't have the space or time right now to perform such an experiment. Maybe once I figure out how to segregate the micro traits out, I could potentially see if this would be an interesting route to go through.

[bower]

I wouldn't take the dogma too seriously.
Don't forget that these conclusions are based on one set of isogenic lines. The general conclusion applied to all determinates is not necessarily true. There are several reasons why the dogma doesn't hold 100% true.
Growth habits are extremely variable. In crosses between determinate and indet lines, all kinds of 'intermediate' growth habits occur between the two extreme points of very small compact determinate and tall rangy indeterminate. The fruit to leaf ratio also varies over the whole spectrum. If you are growing hundreds of F2 and selecting only the smallest plants with highest fruit load as your 'determinates', well yeah you may find some real duds in the flavor department, regardless of parentage.
If you compare a medium to large sized vigorous determinate plant, unpruned, with a tall, linear indeterminate plant strictly pruned as many people do, there's a heck of a lot more leaf per fruit on the bushy determinate. The real difference is how fruit and leaves are laid out on the plant ie in clusters on the bush vs a long linear vine.

I like the idea of a determinate micro, loaded with dense groups of delicious currant tomatoes.
I don't have enough experience of micros to say how difficult or easy that might be. But the key to good tomatoes worth growing is to select for taste as the first criterion. Fred Hempel once said it, "Never select away from taste". Sage advice.
The amount of fruit per bush is not the final arbiter if taste matters.

[KaguyaCloud]

I wouldn't take the dogma too seriously.
Don't forget that these conclusions are based on one set of isogenic lines. The general conclusion applied to all determinates is not necessarily true. There are several reasons why the dogma doesn't hold 100% true.
Growth habits are extremely variable. In crosses between determinate and indet lines, all kinds of 'intermediate' growth habits occur between the two extreme points of very small compact determinate and tall rangy indeterminate. The fruit to leaf ratio also varies over the whole spectrum. If you are growing hundreds of F2 and selecting only the smallest plants with highest fruit load as your 'determinates', well yeah you may find some real duds in the flavor department, regardless of parentage.

I suppose I should be a little more skeptical since there wasn’t that much research on flavor during the publishing of that book. Are there reasons why determinates aren’t as popular for flavor in the home gardening space? It always seems striking to me that the most favorite varieties in this forum are practically all indeterminates, but that could be due to indeterminate varieties being bred for much longer.

And absolutely. Flavor is really the only reason I started my micro x indeterminate project. It’s likely micro-dwarfs haven’t been introgressed with tasty QTL after being isolated strictly for size and earliness.

I just find the idea of a micro with the long trusses of tiny tomatoes from pimpinellifolium kind of humorous. But for the sake of flavor, why not. Although I don’t really have any ideas on good varieties of current tomatoes on the top of my head. I’ve heard that Sweet Pea, Sara Galapagos, and Gold Rush seem to taste good based on other forums.

[bower]

@KaguyaCloud I am terrible for remembering dates/years, but I believe determinate genetics were discovered by breeders, or became of interest to them, early to mid-last century, and were specifically bred for the purpose of mechanical harvest, with the goal that they ripened all at once and were then done after being stripped of fruit by a machine. Thus the majority of determinate varieties are an artifact of industrial era farming. Flavor was not an objective; appearance ( round, red, no green shoulders) was important; and canning qualities in some cases at least. You could say that determinates were bred for "factory tomato" qualities, if you like. Maximum production, definitely high on the priority list. And things like 'uniformity', which is seriously violated by the whole cadre of heirloom beefsteaks. Disease resistance too, and that is probably the one reason that some gardeners who love heirlooms also grow some of the classic determinates, because it ensures a crop for canning when others fail..

Breeding determinates for home gardeners is a recent phenomenon, with goals like "space saving" and "labor saving" re no pruning, but the desire for great taste, interesting shapes and colors is new to the determinate scene, at least on this side of the pond.

[Doffer]

Nebula F1, the sweetest tomato in the world (for what i know), introgresed in a micro dwarf would be perfect