As part of the Going to Seed farmer grant program, Chris Homanics mentored Wojapi TwoBulls for her squash growing project.
Thought this might be interesting as eductional material somewhere, mainly about the Pepo subspecies.
Squash Breeding and Diversity Interview
This is a cleaned transcript of an interview with Chris Homanics, discussing squash breeding, with focus on Pepo species, the Maycock variety, and seed diversity preservation.
Background and Personal Connection to Squash
Fun fact: I like squash. When I was a little boy, I was very compelled by squash and would endlessly eat squash to the point of having orange squash poop. My face has pictures of me smeared with squash. It’s funny because I have an 11-month-old daughter who’s absolutely the same way, just loving that squash.
Squash is obviously from North, South, and Central America. There are certain food plants - Campanula is actually another one - that evolved about 5 million years ago and have been driven by interactions with mammals. This means they have a lot of phytobiochemistry that is very amenable to mammals and makes superior human food.
All over the world, Campanula where it’s found is utilized - Europe, Africa, Central Asia, Asia, North America (not in South America, but there are some other Campanulaceae plants there). There are certain foods that can be inflammatory or problematic, and then there are things that are very neutral for the body and nutritive. Squash is one of these plants - it’s like a prebiotic, probiotic food that’s very nutritive with good health benefits. Issues with squash allergies are very low. It’s also a durable crop for the home gardener to grow and has a venerable history.
Working with Different Squash Species
I actually work more with Maxima than I do with Pepo. Pepo, for whatever reason, hasn’t been preserved as well as Maxima, and that really stinks because when you look at the literature and older descriptions - anthropological descriptions or Native people’s descriptions of what they had - we’re missing a bunch of varieties.
Just all sorts of diversity. Squash suffers from post-1880s consolidation in farms, and since World War II, so many people that were self-sufficient… self-sufficiency isn’t a mainstay anymore. People get squash from the store rather than growing it. If we hadn’t broken this lineage, we would have so many more things - fruit trees, nut trees, varieties, herbs, regional plants. In the south: okra varieties, watermelon varieties. There are so many apple varieties missing, so many squash varieties missing when you look at the old catalogs.
Pepo Domestications and Subspecies
Squash has had two different domestications, at least, for Pepo:
- Pepo pepo: The main domestication (pumpkin-derived types)
- Pepo ovifera: The marrow squashes (what they call courgettes in England or French). These include zucchini, crookneck, that sort of thing.
What’s interesting about the Maycock is that it appears to have both pepo pepo and ovifera in it, but seems to be ovifera dominant when you cross it. When you cross the two domestications, you can kick up bitterness genes, so it might not be in your interest to do that broadly.
GRIN Varieties Discussion
Looking at the varieties Anna got from GRIN:
- PI 9146 from Turkey - looks like mostly pepo pepo, pumpkin-derived types, maybe a pumpkin and acorn cross
- Biska from North Macedonia - looks like a pumpkin
- PI 20-3 - particularly interesting because it said “ovoid, slightly ribbed, dark green, hard rind, wide, flesh usually dark orange and thick.” This is something I’ve been working on with Pepos.
- Tarahumara Indian squash - donated by Glen Drowns, who has pretty good catalogs
- Mandan - also from Glen Drowns, looks like it might be a gourd initially, but actually it’s described as “small rounded, flattened Native American type, heavy producers of cream colored with green or yellow striped fruits. Average quality but great insect tolerance” - it’s in the summer squash section
- Shir Kadu from Badakshan, Afghanistan - looks like a pumpkin type
- Omaha - one of the older pumpkin landraces
The Omaha pumpkin is an older lineage that came from an anthropologist working with tribal members. Someone had bequeathed them seed of that variety, and it became one of the progenitors of modern day pumpkins - kind of like a grandmother to modern day pumpkins.
Breeding Recommendations
Grouping Strategy
My suggestion would be to group the summer squashes together and focus on older landrace genetics rather than adding things like zucchini that you can get easily. Keep older landrace genetics in the mix and make a population of that. Then make a separate population of the stuff that looks like pumpkins.
Working with the Maycock
The Maycock had a lot of traits I hadn’t really seen before in Pepo, or trait combinations. It was super diverse, which I thought was cool. I found it could be reselected for really good summer squash. The winter squash quality is generally not that good in my opinion, but I found the summer squash to have a really nice meaty flavor - almost reminded me of Trombino, which is a Moschata.
Selfing Process
One thing you can do when you have a population of squash is self-pollinate each plant. Squash is tetraploid (has four sets of chromosomes rather than two like humans). This means it has a lot of genetic diversity within it and can benefit from a selfing event.
If you create a population of squash and grow out that population in a field, then self-pollinate each squash and tape off the blossoms, you can take from the plants that look interesting. When you grow that out, you can actually remove from the population weirdness or things that are not good and really focus on the things that are good without hurting the population or diversity. It can be very beneficial to do a couple rounds of selfing in a population.
Technical Background on Squash Species
Cucurbita Pepo Subspecies
According to GRIN taxonomy:
- Ovifera: acorn, crookneck, ornamental gourd, scallop, and straightneck
- Pepo: includes the pumpkin types
Acorn is kind of an outlier because it is ovifera but is a winter squash. Biology’s about exceptions.
Cross-Breeding Challenges
There have been projects where people tried to cross naked-seeded pumpkins with naked-seeded acorns, and it acts like a very wide cross. This is similar to beans (Phaseolus vulgaris), which had different domestications. When you cross North American beans with Central American domestication beans, they have different photosynthetic pathways and become very inefficient.
Historical Example: Zeppelin Zucchini
Years ago, there was an issue where the entire country was getting Zeppelin zucchini seed from farmers in Colorado. Someone had a gourd cross into the Zeppelin zucchini line, but it wasn’t noticeable. It infiltrated the line and created bitter zucchini, contaminating a big chunk of the zucchini available to home gardeners one year. This highlights two problems:
- Need to maintain isolation from gourd types for culinary integrity
- Over-reliance on a small number of producers for seed
Cultural Approaches to Plant Selection
I’ve heard from some Native American people and read narratives about the idea of “shepherding the plant” - not forcing the plant to become anything, but letting it express itself as it is. Kind of like “I love all my children.” Populations started with not a lot of selection pressure - they’re selecting, but not trying to drive it toward some specific direction.
Every time we handle plants, we’re always selecting - how did you start them, when did you transplant them, what did your climate do to them, what did insects and diseases do? There’s always selection happening.
Related Species and Global Context
Other Cucurbita Species
- C. maxima: What I work with most; these are wonderful squashes
- C. moschata: Includes varieties like Trombino
- C. ficifolia: Has black seeds, closely related to C. fraterna
- C. fraterna: A perennial species
Interspecies Relationships
In Central America, Pepo came down from the north and Maxima came up from the south. They met there and formed Moschata. Mixta (our Argyrosperma) is a Moschata backcross to Pepo, broadly speaking.
International Relatives
In India, there’s Ash Gourd (Benincasia), which is one of the closest relatives to Cucurbita. They’ve tried to cross them in India but had to do fancy work to get them to survive - they’re probably not crossable but not far away genetically.
In Europe and Africa, there’s Lagenaria (bottle gourd), which was like the zucchini before zucchini arrived in Italy.
Seed History and Evolution
The whole reason people began selecting squash is because the seed is anti-parasitic - used medicinally. They selected over time for bigger seeds, and size is somewhat tied to flesh size. As they improved seed quality, it became a food source. They’d harvest the seed, pound it, and press out squash seed oil, or boil it and skim off the fats. The flesh quality improved, and it became an “eat-all” plant.
This arc - beginning with plants for medicinal qualities that eventually become food plants - is a theme around the world.
Practical Recommendations
- Screen for gourds - make sure no gourd types are in the mix
- Separate summer and winter types - if people get bitter stuff or use summer squash as winter squash, they’ll be disappointed
- Focus on older genetics - don’t add easily available commercial varieties
- Consider selfing - can help purify and improve populations
- Maintain diversity - these can be diverse populations that serve as bedrock to select from