I am interested in a few odds and ends about tomato breeding, specifically how to get deeper oblate fruit because there is more usable fruit than in standard oblate tomatoes where the stem and core areas are discarded. There are several genes associated with the needed traits. The first is a very small stem/core area. Most heirloom tomatoes - particularly large beefsteaks have a huge core where 1/4 or more of the fruit has to be discarded. Brandywine is an example. Eva Purple Ball is a 2 to 2.5 inch diameter fruit with extremely small core area. It often falls off the vine at maturity due to weak attachment. One of my objectives is to bring the small core area from Eva Purple Ball into a larger tomato with the fasciated (beefsteak) gene.
The second trait needed is to bring in the deeper oblate fruit shape which is associated with round fruit. Druzba is an example of a tomato with the round shape. I want to combine that with larger fruit size which I can obtain from Red Mortgage Lifter.
Then I need disease tolerance, specifically Septoria, Early Blight, Late Blight, Nematodes, Verticillium, Fusarium 1, 2, 3, Tomato Spotted Wilt, and Stemphyllium. I have not found a single tomato that has all the desired resistance, but there are a few that are close. Big Beef Improved appears to have several of the desired resistance genes. Mountaineer Pride has Septoria and Late Blight.
Last and most important, I need really good flavor with just enough sugar to balance the tartness. I can get the sweetness from Crnkovic Yugoslavian and the good flavor from Lynnwood. I also want the intense red color that comes from the high lycopene gene which can be found in several varieties such as Burgundy Traveler.
So I guess I get to start a serious tomato breeding program this year since I have all the required varieties growing. Here is a relevant article worth reading about genes involved in tomato shape.
There is an active tomato breeding and genomics program at UNC with quite a catalog of traits, breeding lines, etc. I last had a look at it 8 years ago. Perhaps you’ve seen it?
I spent an hour on the phone with Randy Gardner. He provided a lot of insight into the breeding choices I am making. I got the link to the article on fruit size/shape from Sam Hutton.
One other gene I am interested in but don’t know how it will play out in breeding is present in a specific line of Dr. Carolyn Pink cherry. It has an indention where most tomatoes have a blossom end scar. I want to eliminate blossom end scar in the tomatoes I am breeding so am considering bringing the gene over into a larger fruit. It helps a lot that Dr. Carolyn Pink has very thick flesh on the outer wall of its fruit.
That sounds super interesting to me. I have been breeding new tomatoes for five years now - all on a backyard scale.
I have set up my breeding program and planned my crosses based on the understanding of the process that I got from Carol Deppe’s books.
The wonder you experience when you find all kinds of new shapes, colors and sizes among your seedlings really doesn’t get old over the years. It is a passionate but is, so rewarding thing to do!
The most difficulty I have experienced, or the thing I am the least sure about is the selection for disease resistances. It is difficult to combine them and at the end of the season it really isn’t so clear cut which plants are evidently the most healthy. So to select for disease resistance based on phenotypic observations alone is sort of hard - the specific plants I choose to take to the next generation could have been lucky, or gotten a bit more fertilizer or water, and it takes a whole year or often two years of growing their offspring before you get confirmation that the plants actually really carry a genetic resistance. And that is only for one disease!
Have you got any ideas on how to combine so many traits from so many parents into a single variety? And how many generations and crosses do you think it will take to get the result you want?
Combining this many traits is at minimum a 10 year breeding effort. I will make at least 5 crosses this year. As an example, I will probably cross Eva Purple Ball X Red Mortgage Lifter. The intent of this cross is to move the small core from Eva Purple Ball into a much larger fruit size. At the same time, I can select for pink fruit, Eva is pink, and pick up VF tolerance from Red Lifter. I will also make a cross of Crnkovic Yugoslavian X Lynnwood which should segregate for both larger fruit and improved sweetness. Repeat that for the other traits pairing up parents. Next year, grow out the offspring and save seed. Third year grow the F2 seed and watch things segregate. Then start crossing the offspring to combine the traits.
You are correct that disease resistance genes are very difficult to select without DNA tests of some sort. Current breeding programs use marker assisted selection to stabilize traits. There are also programs that use mass challenge tests where the disease organism is cultivated and deliberately sprayed onto the plants.
This is an interesting thread. I am planning to start some indoor tomatoes soon. I am interested in beefsteak and plum types. I also want determinate and indeterminate varieties. I currently have seeds for Black Krim, Aunt Ruby’s German Green, Yellow Brandywine, and San Marzano. I am thinking about using Roma and Campbell 33 for the determinate genes, unless somebody know a reason why I should not. There do not seem to be nearly as many heirloom indeterminate varieties to choose from.
I am hoping to to achieve some degree of stability in 5 or 6 years. My only plant breeding experience is from breeding heterozygous medicinal herbs over a 5 year period. I am confident that I can grow tomatoes successfully indoors. This first Winter should help me determine if LEDs will be sufficient, or if they require the ‘horsepower’ of an HID lamp.
I grew tomatoes every year growing up in Ohio, but I do not remember ever treating them for disease. Bugs, but not disease. Anything I breed here may not be suitable for areas with high disease pressure. I am fine with that, because I am not trying to produce a commercial cultivar. For me, the process of breeding plants is just as satisfying as achieving my goal. I do not gamble, but every seed is like a little lottery ticket.
How are your crossings doing? And are you growing the F1 generation now to harvest F2 seeds this winter?
You have probably already thought of it, but I think that the new varieties should have extra dark red flesh with extra Lycopene. This gives the fruits a more attractive appearance with the extra dark red flesh and is healthier.
I am currently working on the hp-2 dg gene, but the ogc gene would also be very suitable.
(looking for a way to select the seedlings for these genes)
I think Randy Gardner has linked the crimson ogc gene to the Rin gene through crossover through a large selection program for extra long shelf life. (Mountain Magic)