Interestingly, one of the SSE members posted a rant about how nobody bothers isolating their tomatoes, so all the seed they get is crossed up. I bet it has a lot to do with the ecology of the local area.
You don't want self incompatibility in tomatoes. It leads to reliance on pollinators to set fruit and overall very low amounts of fruit set. I've grown several self-incompatible lines and would not want those genetics in a tomato I grow for fruit.
Post by Joseph Lofthouse on Feb 5, 2016 18:55:08 GMT -5
I would love self-incompatibility in my tomatoes... I am working towards that end. I grow tomatillos that are self-incompatible, and fruiting is prolific. When I eventually stabilize self-incompatibility in tomatoes, I will select for varieties that are highly attractive to pollinators. I don't poison my garden, so there are plenty of pollinators around.
As an intermediate step in that direction, I am selecting for bigger flowers that may attract pollinators better. I am selecting for higher pollen production to attract more pollinators. I am selecting for open anther cones, and exerted stigmas so that foreign pollen can reach the style easier. Restoring self-incompatibility to domestic tomatoes is a long-term project, but I get a little closer every year.
I value the goal of self-incompatibility in tomatoes, because it would enforce out-crossing, thus promoting automatic hybrid vigor in each generation, and with all the recombining going on every generation, I think that there would be more opportunities to select for resistance to blights and pests.
Silt/clay, high-altitude, super-arid, sun-drenched, irrigated-desert garden. Cold radiant-cooled nights. ~100 frost free days. Grow most of my own locally adapted landrace seed. GDD10C ~1300. Author of Mother Earth News: Landrace Gardening Blog.
Do self-incompatibility genes even exist in tomatoes?
Some of the wild tomato species have self incompatibility genes. S. habrochaites seems to me like the easiest to acquire and use for crossing. For me, it might also provide some frost/cold tolerance. Basically, you gotta use pollen from the self-incompatible species to pollinate domestic tomatoes, and you gotta use enough pollen donors to get a number of different incompatibility genes. Then you gotta reselect for self-incompatibility, and maintain a high enough population to keep the various incompatibility genes around. And you also gotta reselect for flowers of the right shape to encourage promiscuous pollination. One plant won't be sufficient. You gotta maintain a population.
The mathematics of finding the right combination of diverse incompatibility genes, and promiscuous flowers shows that it isn't a trivial project, but it's certainly within reach. They would also need to be reselected for fruit and architecture preference.
Back to the 'diversity within a variety' question. There are lots of ways it might eventuate. In my own breeding work with peas, I've sometimes lumped seed batches together to get more seed more quickly. If I'm after a disease resistant tall purple snow, I've lumped seed from sibling progeny that had the desired characteristics - tallness, purple, low fibre, and survivorship as a measure of disease resistance. I'm not really concerned with seed coat colour for example, or whether it homo or heterozygous for flower number. A case in point - I grew Yakumo snowpea, and liked it - it had buff colored seeds. Bought some more seed from a different source, and found the seed coat colour was green. So either it originally had both seed colours, and someone has grown out a line from the buff ones, and someone else grew a line from the greens, or something else altogether different... who knows? Chuck in some genetic drift, a bit of original variability, a bit of outcrossing, some epigenetics and away you go...another example, one of the purple pod genes in peas spontaneously 'throws' back to green, reportedly 5% of the time. I imagine there are all sorts of genes that do the same in many crops, some of which may not be readily apparent. Just some thoughts. T