Crossing the bitterness out of cucurbita pepo egg gourds

[Seeds]

Mark Kidd
2022-11-14T08:00:00Z
Background==

From my understanding, evidence from archaeology, genetics, and molecular biology strongly suggests that Cucurbita pepo was domesticated twice. One group of squashes that includes pepo pumpkin, calabaza, and marrow/zucchini was likely domesticated in Central America, and another group that now includes crookneck, acorn, scallop, and ornamental gourds was likely domesticated somewhere between Texas and the mid-Atlantic.

There is information scattered across the web and in academic papers about the separate C. pepo domestications. I found the squash chapter in “Rivers of Change” to be an easy-to-follow narrative account of the proposed history of the pepo species, and it can be read via Google’s preview of the book at [ Google Books ]

My goal==

I am interested in creating as diverse of a grex of edible squashes as possible from the Ozark/Atlantic lineage. As a secondary goal, I am interested in whether there are desirable traits that can be added from genetically related feral and wild-type squashes.

I have not undertaken a project like this before, and I am particularly interested in advice and reference material with how I might approach adding genetics from the wilder varieties. I have not yet unlocked the squash section of the curriculum here, but I will certainly do so over the next week or two!

For my project, I have been saving, buying, and swapping seed from these varieties with the intention to encourage them to freely cross-pollinate in 2023:

• Large green acorn
• Small yellow and orange acorn
• White scallop
• Yellow round
• Yellow crookneck

I also have seeds of ovifera varieties that may or may not be bitter (I have not grown any of these yet):

• Nest egg gourds collected from two populations in Missouri
• Tennessee spinner gourds
• Common ornamental ovifera gourds

Because I live in Kentucky, my wish list includes feral nest egg or pear gourds from my state, but I have not found a source yet. Please let me know if you are aware of any opportunities!

[Seeds]

Joseph Lofthouse
My only suggestion is that if you introduce poisons (bitterness) into your population, then you have to select againstt them later on.

William S
I suspect the “Mandan” pepo squash sold by Sandhill is a North American domesticate group. I crossed it last year to both Lofthouse crookneck and Lofthouse zucchini a marrow type. Honestly the seed from the zucchini cross look like better seed. I wonder why folks interested in this two centers of domestication story want to keep the two groups separate? I want to keep the “Mandan” squash as the mother of my grex because it is an amazing short season squash with deep ties to my region. I’m excited for the next generation which should segregate wildly.

Mark K
For me, I am interested in dedicating one squash plot to an ovifera grex because I live in the general area where the ovifera varieties were domesticated. My hope is that this grex will be well-adapted to this area while producing lots of summer squash. There’s no reason in my mind why I wouldn’t also cross with the C. pepo subsp. pepo varieties too, albeit in another plot.

Mandan was on my list of interesting C. pepo squash, but I hadn’t looked into it too closely. Honestly it was because it looked more like a pumpkin than I associate with the ovifera morphologies, but it sounds like I need to take a closer look at Mandan. Thank you!

[markwkidd]

I have narrowed the focus of this project quite a bit. The goal at the moment is to cross egg gourds with white patty pan squash, then back cross the progeny with egg gourds. Offspring from the back cross will be selected for conformity to the egg gourd shape and non bitterness.

If I have understood what I’ve read about the genes for bitterness, the non-bitter genes should be dominant and therefore this will be a relatively straightforward project. If I do have successful crosses in the F1, many or most of the third generation after that should be free of bitterness.

I plan later to add some research links and photos to this thread. At the moment, I have two strains of egg gourd growing alongside the patty pan squash. I plan to remove male flowers from the egg guard vines.

[markwkidd]

This photo depicts the largest bed where I am growing squash for this project. The vines with plastic ties are egg gourd, the others are white scallop squash.

In addition to this bed, I have two others. They are all at this point where they have a few true leaves but haven’t flowered. They haven’t grown very quickly, but they were the last of the squash I planted this year so the fact that they are small is mitigated by the late planting.

[markwkidd]

I have three plantings total, and they are all at a similar stage. The smaller group on the left of this photo is the egg gourd, the slightly larger group on the right is the white patty pan squash.

In general, the patty pan has been flowering for 8 to 10 days. None of the egg gourds are flowering yet. I’m trying to remove male flowers from the egg gourds so I feel like any morning now I will spot one that I need to detach.

I’ve seen a little bit of powdery mildew on patty pan squash and because it was widespread last year, I assume it’s endemic to my garden. That’s one of the pressures this project will have to be able to handle.

[markwkidd]

I’m coming to realize that if I wanted insects to make this cross, I have planted in the wrong order if I want the egg gourds to be the mother.

The egg gourd vines are now starting to produce male flowers which are not open yet. None of them have any female flowers so far.

I have not manually pollinated squash, but while I ponder this situation, I am gathering some male patty pan flowers to dry out and serve as a pollen bank for the egg gourd vines so that I don’t inadvertently lose the opportunity later.

There is definitely powdery mildew on both egg gourd and patty pan individuals, but they still seem to be doing okay with it so far.

[VeggieSavage (Professor Porcupine)]

Has anyone tried Eating Squash Leaves, to taste test for Cucurbitacin? Think about it… If the Leaves Taste bitter, I’m almost Certain the fruit will Taste Bitter too. I have not confirmed this but I suspect it is universally true for all Cucurbita spp.

Might Legit help you breed out Bitter Cucurbitacin much Faster. Also you wouldn’t have to sacrifice your entire Seed Collection for the year like how Lofthouse did.

Regardless All Squash/Cucurbita spp. Have Edible (Raw or cooked) Leaves, Shoots and Flowers so long as they are not bitter. Only problem is some Squash have Texture issue but Cooking them solves the texture problem.

[markwkidd]

Great idea, I have not thought about this and I have no idea. Thank you!

[VeggieSavage (Professor Porcupine)]

Give it a try and tell me what you think! I want to hear if this is true from other people’s experience.

[markwkidd]

No updates, just research notes. In the past I haven’t kept a log of my squash bitterness research, so I’m out looking for references. In particular I’m trying to learn about the two theories about Cucurbita bitterness: a single dominant gene, or several recessive genes that interact in a more complex way.

Maybe this question has been solved, but as of the 1980s it was still an open question This is a short summary but it has some information I would like to remember.

Interaction of Cucurbitacin Genes. R.W. Robinson, A. Jaworski, P.M. Gorski, and S. Shannon. 1988
https://www.ars.usda.gov/ARSUserFiles/60800500/CGC/CGC%2011%20(1988).pdf#page=31

A single gene, cu, of Cucurbita pepo is known to govern cucurbitacin B content of cotyledons (4). We confirmed this, and found that cu determines cotyledon content of cucurbitacins D, E, and I as well as cucurbitacin B. Classification for cu can be made by tasting cotyledons. Cultivars such as ‘Scallop’ and ‘Straightneck’ that are recessive for cu have nonbitter cotyledons, whereas Zucchini’ and other cultivars dominant for cu have bitter cotyledons.

In this respect, the cu gene of Cucurbita pepo is similar to the bi gene of Cucumis sativus, since both produce a phenotype of nonbitter cotyledons. They differ, however, in gene action. Cucumber gene bi completely blocked cucurbitacin biosynthesis, while squash gene cu reduced but did not eliminate cucurbitacin formation.

Another fundamental difference between Cucurbita gene cu and Cucumis gene bi is that cu is not epistatic to the dominant gene in the species for bitter fruits. The F 2 of C. pepo cv. Early Prolific Straightneck x C. texana segregated 3 bitter fruits: 1 nonbitter, not in the 9:7 ratio that would be expected if cu were epistatic.

[markwkidd]

Another hypothesis for bitterness genetics arising from a cross between argyosperma and pepo:

Inheritance of Fruit Bitterness in a Cross of Cucurbita mixta x C. pepo

Inheritance of Fruit Bitterness in a Cross of Cucurbita mixta × C. pepo

A cross of ‘Green Striped Cushaw’ pumpkin {Cucurbita mixta) x ‘Goldbar’ hybrid summer squash (C. pepo), neither of which have bitter fruit, produced an Fx having extremely bitter fruit. Inheritance data suggest that fruit bitterness in this cross is conditioned by three dominant, complementary genes with two contributed by ‘Gold-bar’ and the third by ‘Green Striped Cushaw’.
…
These data indicate that three dominant genes are required to produce bitter fruit, with ‘Goldbar’ being homozygous for two of the three. The recessive gene at the third locus may be the genetic mechanism described by Rehm and Wessels (9) that some times suppresses the development of cucurbitacins in fruits produced on cucurbit plants that developed from bitter seedlings. Chambliss, et al. (3) describe a similar recessive, suppressor gene in watermelon. ‘GS Cushaw’ lacks the two dominant genes required for bitterness found in ‘Goldbar’ but possesses the third dominant gene required for the development of fruit bitterness. The unusual condition demonstrated in this interspecific cross is that three dominant, complimentary genes from nonbitter parents interact to produce an ¥1 having bitter fruit.
…
Fruit bitterness in this cross is entirely dependent upon dominant genes, therefore there will be no problem with bitter-fruited progeny arising from the selfing of F2 or back-cross plants having nonbitter fruit.

Bitterness in cucurbit fruit has been shown in several studies to be dominant to nonbitterness. Possibly, the edible, cultivated cucurbit cultivars originated from wild bitterspecies following recessive mutation (4). If a sequential series of biochemical reactions, each under gene control, is necessary for the production of cucurbitacins in cucurbit fruit, mutation of any one of these genes could interfere with cucurbitacin development and result in the production of nonbitter fruit.

Although several genes affecting bitterness and the suppression of bitterness in fruit have been identified in this and other studies, it is possible, and even likely, that cucurbit species and cultivars exist that are nonbitter because of other, as yet unidentified, recessive mutations.

[VeggieSavage (Professor Porcupine)]

@markwkidd

A single gene, cu, of Cucurbita pepo is known to govern cucurbitacin B content of cotyledons

Wait hold up, it said in the Cotyledons!? That might just explain why PFAF Says “The sprouting seed produces a toxic substance in its embryo[65].” I’m not the only one who sees this connection am I?

@markwkidd

Cultivars such as ‘Scallop’ and ‘Straightneck’ that are recessive for cu have nonbitter cotyledons, whereas Zucchini’ and other cultivars dominant for cu have bitter cotyledons.

That would explain why slugs avoided some squash seedlings over the others (If snails are affected by Cucurbitacin).

So it is true, You can Detect Bitter Cucurbitacin via tasting the Leaves! Although now we know not to cull plants based on the Cotyledon Taste, but based on the actual true leaves taste. I’ve eaten Squash leaves of all my plants (So has my Groundhog, he approve of every single leaf ), none of them bitter but some have a better taste then others.

I also wonder if this extends to the Flowers, I’ve ate Cucurbita pepo & Cucurbita moshchata male flowers, both have good taste with the Pepos being my favorite. But the Cucurbita maxima has a weird (But not awful) taste, it wasn’t bitter just a completely different vegetable flavor and wasn’t sweet like the pepo was.

@markwkidd

The unusual condition demonstrated in this interspecific cross is that three dominant, complimentary genes from nonbitter parents interact to produce an ¥1 having bitter fruit.

Thank you for finding this Valuable information. The advise her is to just cull any bitter fruits and only save the non bitter types. Hmm… This also got me thinking, maybe
1 gene controls if Cotyledons would be bitter
2 gene controls if leaves will be bitter
3 gene controls if fruit will be bitter

It could help understand why my water leaves tasted bitter (Hence why it Survived the Ground Hog).
The big question to ask is, what about the gene that affect bitterness in the seed? Because If i recall correctly, domestication of squash 1st started by domesticating non bitter seeds. Then after years & years of selecting for non bitter seeds a mutation occured that also made the flesh of the fruit non bitter and so on and so on until WHUALA, we have modern cultivars.

I’ve also noticed (Tho I may drawing wrong conclusions) that the more the groundhog ate my squash plants, the more spikeyer the younger leaves became of my pepo type. Maybe it was just simply maturing or maybe Groundhog had an influence (Hard to confirm without control).

[markwkidd]

@VeggieSavage

So it is true, You can Detect Bitter Cucurbitacin via tasting the Leaves! Although now we know not to cull plants based on the Cotyledon Taste, but based on the actual true leaves taste. I’ve eaten Squash leaves of all my plants (So has my Groundhog, he approve of every single leaf ), none of them bitter but some have a better taste then others.

I interpret that part of the research as indicating that some bitter individuals would have bitter cotyledons, but not all, depending on which of the bitterness loci were present for the particular individual.

I have been tasting young leaves from the white patty pan and the egg gourd plants. I can’t at this time speak to whether that can be a viable way to distinguish between bitter and non bitter fruit.

• I have never tasted bitter Cucurbit fruit. This year’s crop will be my first chance to make sure I know what the flavor is
• Among the leaves I have tasted from a total of five different plants, including (presumably bitter) egg gourds from two different sources, I haven’t tasted anything that I wouldn’t consider eating by choice in the future. One egg gourd leaf I tried was fairly bitter, but no more bitter than something I would consider putting into salad. It was kind of an interesting numbing bitter, but less than many mustards I’ve tasted

[markwkidd]

It seems like it has been a rough year for growing squash in my region. It was a little rough at my garden, anyway. Two of the egg gourd vines are producing fruit, which I’m very grateful about.

If I could change one thing about my approach to the season, it would be to have covered female flowers with bags and pollinated manually. I would say that removing male flowers is insufficient in a case like this when it’s essential to have a cross. However, I do have some belief that there are some crosses among the four fruits that I expect to harvest.

I’m uploading a few photos of the patty pan squash that I am using to pollinate the egg gourds. I have found myself tempted to try to grow a few of these seeds indoors over the winter.

[H.B (HasBean)]

Following with interest. Bitter melon is one of my favorite vegetables. My understanding is the bitterness comes from the cucurbitacins and momordicines. Since finding this out I can’t help but wonder if the case against cucurbitacins has been overstated the same way breeding against bitter tastes appears to have been overdone.

I’d probably try the F1. Heck, I might try the egg gourd

[markwkidd]

I have reason to hope this fruit was pollinated by the patty pan. It is extremely bitter. After removing seeds, I placed a tiny amount on my tongue for a second and removed it.

A few seconds after that I tasted an incredibly bitter flavor that lasts for a while but eventually fades. I don’t feel that I was sick or poisoned, but I’m very glad that I didn’t swallow it or put any more on my tongue at once.

The flesh smells like a bland pumpkin. Even though it wasn’t seasoned in storage, I don’t think this would be very much sweeter with time. This one is solid with flesh, which seems promising for potential summer squash use if it wasn’t bitter. I placed a United States penny next to the seeds for scale in the photograph.

[markwkidd]

One of the seeds portrayed in my previous post has sprouted indoors. This is an image of its current progress.

I tore about 1/4 of one of the cotyledon leaves and ate it. It was totally palatable (nothing like the the ripe fruit which was incredibly bitter) but I could definitely detect a bit of the “numbing tangy flavor” that I am associating with palatable amounts of cucubitacin.

Maybe it will be easier for me to judge bitterness from cotyledons and leaves when I have more experience, but for now I don’t think that is an indicator I will be able to use. On the other hand, the juice and flesh of the ripe bitter egg gourd continues to be unmistakable. Breathing it in could be compared to menthol, somehow a little like vapo-rub. May not be good for a person, I only know this from processing the fruit; makes me want to be sure to wash my hands once I’m done handling pulp and wet seeds.

I planted three or four of these seeds, and while I’m not positive I’ll be able to raise them all the way till they form fruit indoors this winter, I will go as far as I’m able under my circumstances. Maybe I’ll be able to make it through another generation indoors, although it would be self- and sibling-pollinated.

[markwkidd]

Today I harvested the last of the egg gourds representing potential crosses. It’s a little small but I have reason to hope there will be some viable seeds. That makes five potential crosses to work with, which is probably enough for me to manage.

The final egg gourd is portrayed next to one of the fruits from the patty pan squash vines that are the intended pollen source for the cross.

[VeggieSavage (Professor Porcupine)]

@VeggieSavage

ikeyer the younger leaves became of my pepo type. Maybe it was just

Bitterness in Cucurbita is well behaved (It will let you know Loudly!). I’ve been eating Male flowers of my Cucurbita maxima and the bottom end (The Green Part) of my Flowers were bitter but especially the part with the stamens, those were extremely bitter.

Strangely the leaves weren’t bitter at all, mostly the stamen of male flowers were. Seems like different parts via breeding can be turned off or on. The leaves weren’t bitter at all, the young leaves were pretty good but not as good tasting as Cucurbita pepo.

Also Cucurbita pepo didn’t have bitter flowers whatsoever, even has a sweet taste thanks to the nectar at the bottom of Cucurbita pepo male blossoms.

As for Squash Greens go, Cucurbita pepo wins by a long shot in flavor, so long as they’re young and easily pinchable, I enjoyed their flavor very much. Makes me want to make a Squash Landrace for the Greens & Flowers alone.

[VeggieSavage (Professor Porcupine)]

Interesting Question, But I don’t really like bitter foods. I do know that the bitterness in plants is usually the part that is also the medicine (I’m not a medicinal plants expert by a long shot!).

I’m surprised to hear Bitter Melon is among your favorites? How did you make it taste, did you cook the bitterness away?

In terms of breeding the bitterness out of Cucurbita, I don’t think it was overdone cuz I’d rather play it safe and enjoy the foods I’m eating. It is a well behaved toxin cuz the Bitter taste is STRONG AF (Taste like Ear Wax that sometimes Lasts like the Warm Burn of a pepper but instead of heat, it’s bitterness). I supose small amounts couldn’t hurt too badly but why bother.
The Native Americans who first bred out the bitterness probably did so for a good reason, we could experiment to find out the same reason again, tho I wouldn’t really want to.