Solanum pennellii

[Joseph Lofthouse]

Of the wild tomato species, Solanum, pennellii has been the most difficult for me to work with.

1- The seeds are very small. Therefore young plants are also small, and delicate. Highly susceptible to damping off.

2- The root system seems weak and fragile. Seems like a little disturbance kills the plant. The plants haven't sent out roots from the stem, so growing cuttings is problematic.

3- The type of soil it grows in has a huge impact on plant growth.

I managed to grow a respectable amout of seed this year in pots, that were shaded mid-day, and received morning and afternoon sunlight. The potting mix was 100% compost. Not just any compost, but a specific batch of compost, which is the only type of compost/soil that the plants did well in out of about a half dozen that I tried.  Solanum pennellii seems to do better if it is misted rather than irrigated, so I watered with a jet of water across the plants, rather than irrigating the soil.

So for those of you attempting to grow Solanum pennellii, I highly recommend starting seeds in a dozen different potting mixes, and then choose to grow your population in the one in which it thrives. And minimize transplanting. Maybe it wouldn't be an issue in a high humidity climate, but for me, where it is super arid, I need every advantage I can get.

I have yet to successfully grow a S pennellii plant in an open field that receives once a week irrigation, and full sunlight. I did raise one plant this year in which I put the tomato and pot directly into a bed, so that the plant could have it's preferred soil, and stretch into the native soil as needed for additional
moisture. But the plants that were grown in pots only did better.

Solanum pennellii is self-incompatible, and the shape of the anthers is cylindrical rather than conical. The stigma is exerted to highly exerted. The leaf shape is highly conserved in the offspring of interspecies hybrids with domestic tomatoes.

I grew F2 hybrids this summer of a cross between domestic tomatoes and S pennellii (Thanks Andrew). There were huge differences in vigor between plants.

[William S.]

I planted some seed for pure penellii you sent and got a single seedling. It died shortly after transplanting.

Of the F2 penellii Andrew produced I had about a dozen plants but only one produced seed.

I suspect that one plant will have had a tremendous selection pressure and it's offspring may have a much better success in my 2019 garden.

[Andrew Barney]

I tried planting pure pennellii seedlings once and failed miserably. The seedlings were tiny and thus were slow and weak. I think died from a weird combination of lack of water and too much water. Misting would have helped. I wonder if nearly pure sandy soil would have helped. I'm out of seed for it but i like the conserved leaf shape and would like that trait backcrossed and maybe some of the waxy leaves preserved or combined with peruvianum traits. Pennellii is supposed to conserve water during the day as drought tolerance and open pores open at night,  so night misting might work best. Peruvianum is supposed to have really deep drought tolerant roos,  so a combination of those traits would be highly interesting. All of the wild tomato species are nearly impossible to root cuttings (i have managed one rare one of peruvianum), but having a joint and/or pre-scarring some tissue may help). The pennellii-[domestic] hybrid F1s grow like monsters and root cuttings mid-way between wild and domestic.

[Joseph Lofthouse]

Pure sand was one of the potting soils that I tried with S pennellii. I also tried various mixes of sand/coir/compost. Growth was tremendously better in one of the pure composts. The differences in growth between different potting soils was dramatic. It was obvious to see which soil they thrived in. Thus I recommend growing S pennellii in two phases: grow some sacrificial plants to determine which soil is best, and then to grow the real plants in that soil.

I have one bin of soil which I am reserving only for the purpose of growing S pennellii.

 

[William S.]

Maybe we should learn to graft tomatoes and graft the pure pennellii onto the hybrid?

[William S.]

One small branch of my penellii f2 I dug up is wilting oddly. I left it in a saucer of water for a few days. Maybe it's getting over watered.

[Andrew Barney]

One small branch of my penellii f2 I dug up is wilting oddly. I left it in a saucer of water for a few days. Maybe it's getting over watered.

It's possible. The pennellii hybrids do not root the quickest when taking a cutting,  but compared to most wilds they at least root. I suppose that is also a trait that could be highly variable and segregating in an F2 since Joseph also saw vigor highly segregating.

[William S.]

My pennellii are doing very well this year.

I have an pennellii plant from seed from Joseph that he grew the mother of isolated in a crossing matrix so it may be a cross that is doing fine and setting some fruit. I have an F1 pennellii from a single seed Andrew sent that is setting lots of fruit. A extremely vigorous putative three way cross with habrochaites from seed Joseph sent. These three are within easy pollination distance of one another. Have only one plant from last years seed. Nothing special about it. Have a lot of F3 plants, except for three way, not noticing a lot of fruit set yet, but blooming well. Some are forming rigid upright bushes and others are quite sprawling.

[Andrew Barney]

That's awesome. I only have one F2 plant this year,  it is large and doing well and setting some fruit.  I tried crossing it with pollen from Joseph's big hill. What what be really awesome would be pennellii x peruvianum hybrids.  And mine kinda resembles some peruvianum traits,  but is hard to tell.  What I can tell you is the bumblebees that year were all over the peruvianum flowers and every so often they would visit the pennellii. So if they are compatible,  some or all of my F2 line could have peruvianum genetics. But I have no idea.

[William S.]

Three way, f1, and mostly penellii plants are setting fruit well. Haven't found a fruit yet on any other penellii F3 plant. Including the lone descendant of last year's dozen plants. Maybe they are contributing pollen though. This is the second year of reproductive difficulties in Penellii crosses for me.

Some thoughts:

Try hand pollinating more?

plant more plants next year. Including more from packets of pure penellii seed. Try to get more S alleles into population.

Maybe my complex of bees lacks a species that's particularly effective?

Anyone else experiencing reproductive difficulties with penellii?

[Andrew Barney]

Three way, f1, and mostly penellii plants are setting fruit well. Haven't found a fruit yet on any other penellii F3 plant. Including the lone descendant of last year's dozen plants. Maybe they are contributing pollen though. This is the second year of reproductive difficulties in Penellii crosses for me.

Some thoughts:

Try hand pollinating more?

plant more plants next year. Including more from packets of pure penellii seed. Try to get more S alleles into population.

Maybe my complex of bees lacks a species that's particularly effective?

Anyone else experiencing reproductive difficulties with penellii?

when i tried buzzing the pennellii hybrid flowers this last winter i noticed no pollen when compared to a domestic and galapagense. So, yeah, perhaps try hand pollinating more. A lot more. i had some success with that experiment using the walnut oil and water idea. It also seemed like the pollen needed something like that to stick to the stigma.

[William S.]

Wonder if it is a pollen sticking sort of issue. I think my base response to this problem in some ways is that I am liable to get penellii seeds from three great penellii descended plants. So forget the rest. Still why so problematic in the F3? Seems like each generation should be more sorted. Also I should really check every plant for berries, we might be talking about a dozen plants again. Maybe I've missed another producer.

Also of my three plants that are producing for sure. One of them came from a packet of penellii seed Joseph grew last year but isolated from other penellii plants so could represent a hybrid. If so it seems mostly penellii but it is surviving without much care. Also I have made a habit of not watering that side of the bed. The roots should theoretically be able to reach water, from the soaker hose on the other side, but none gets right to the plant. So Josephs efforts to adapt penellii seem to be paying off.