I have been reading about parthenocarpic squash over the past two months. The idea of a plant that sets fruit without requiring pollination is useful at least in-theory, but from my experience trying to find seeds for parthenocarpic squash varieties, I've found that the only readily available parthenocarpic squash varieties are proprietary hybrids.
I'm hoping there's at least one member on this forum who's familiar with parthenocarpy genetics in Cucurbita sp. especially Cucurbita pepo. In the meantime, I will try to find journal research on this topics.
If the parthenocarpy trait must be heterozygous in order to be expressed in the daughter plant, then two stabilized inbred lines will have to be registered with the OSSI.
That was fast. I've already found one journal article on parthenocarpy in C. pepo. I'm hoping I find more.
http://www.funpecrp.com.br/gmr/year2005/vol1-4/gmr0093_abstract.htm
Based on the first journal article that I posted, it appears that the Whitaker squash mentioned in the article is an inbred line, so it might not be as hard as I thought to stabilize the parthenocarpy trait in a variety of squash. Of course, if I were to develop an open-pollinated landrace, I would need to be reasonably sure about the presence of wild and volunteer C. pepo squash in my region as well as rhe presence of any neighbors also growing C. pepo squash. There is also the inherent problem that parthenocarpic fruits will by their very nature produce fewer fruits with viable seeds per plant.
Yeah. My plan is to introduce parthenocarpy into my pepo squash landrace, and then see what happens. I'm not sure yet whether I'll like it or not (I'm guessing I will, but we'll have to see if there are any connected negative traits I don't want!). I got a Burpee hybrid called Sure Thing for that purpose.
I also suspect that another Burpee hybrid I planted last year, Butterstick, was parthenocarpic, even though it didn't claim to be -- it had way, way more female flowers than usual, all of which set fruit immediately, and I'm pretty sure they weren't all being pollinated. So it may be worth checking some hybrids for parthenocarpy; it may be present even in varieties that aren't labeled that way. I call that a bonus!
I really like the idea parthenocarpy mainly because of the end of the season. I have plenty of pollinators all summer, and we don't get much (or sometimes any) rain, so most female flowers get pollinated during the summer. But when it gets colder in fall, and/or we get some rains, the bees stop being so active, and I get far less fruit set. With summer squash, that matters!
On top of that, if a squash is parthenocarpic, I can put an unheated hoop house on top of it and get it to sail through a few light frosts, which means an extra month of production until the first hard freeze. I can't do that if the plant needs pollination by insects, however.
So yeah, it's not a trait I need, but I suspect it will be very useful in fall. If I can mix parthenocarpy with an extra long shelf life even when harvested unripe (which is a trait I have in my spaghetti zucchinis -- eight months of shelf life so far, and counting!), that may make for some great winter food production during the last month of growing season before snow starts coming.
My interest is in having squash with female flowers as some years my plants have none.
So I started reading. About 1985 Rutgers started crossing plants that produced a lot of female flowers - Caserta, Early Prolific Straightneck and Precocious Early Prolific. However, there were no females in the F2 of PEP x Caserta.
They developed NJ260 which begins to flower as a male but soon becomes intensely female.
I bought Caserta and Early Prolific Straightneck but couldn't find a source for the Precocious one.
Partenon F1 is a parthenocarpic zucchini. I didn't find seeds of that, but I did get Raven which has a concentrated fruit set. That sounds as though it has lots of female flowers, so I hope I'll get some zucchini this year.
I grew Early Prolific Straightneck last year. I wasn't impressed. Out of the five plants I grew:
- One died quickly. It seemed it couldn't handle the competition of being planted quite near my spaghetti zucchinis. Good riddance, then. My spaghetti zucchinis were much more closely crowded together, and they all did fine.
- Two did okay, but produced fewer fruits than my spaghetti zucchinis. They were also much smaller fruits, so I got only about a quarter as much food production per plant.
- One had only male flowers! I was downright incredulous! I kept on being patient and waiting for fruits to appear, and nothing. Just lots of male flowers. Two months after all my other pepo squashes had started fruiting, I finally pulled it out in disgust. I do not want andromeciousness in my pepo population, thanks.
- The fifth and final plant was actually what I was promised on the seed packet. It had loads of female flowers that produced loads of fruit.
All five plants also had the sharpest, nastiest pepo squash thorns. And it wasn't especially early -- it started fruiting at the same time as my spaghetti zucchinis, which are about average. And honestly, the taste was okay but not great. My spaghetti zucchinis were far better. Overall, Early Prolific Straightneck is not a variety I plan to grow again.
So yes, it can be highly productive, and it probably originally was, but my suspicion is that it's been poorly maintained, and now contains a whole lot of garbage DNA. It definitely wasn't early -- that one plant that was productive started fruiting at the same time as my spaghetti zucchinis, so I'd say right at the usual time.
Overall, if you want something that fulfills the promise of Early Prolific Straightneck, I would recommend trying Butterstick. It was early, extremely productive, had tiny thorns, loads of female flowers, I think it was parthenocarpic, and it's also a straight yellow pepo variety. It's a hybrid, but I'm sure you could cross it with something to breed your own variety -- maybe Early Prolific Straightneck, for example!
There's a thread (https://www.facebook.com/groups/950816328591402/posts/1645230525816642) in the Heirloom Cucurbits FB group about parthenocarpic squash. There a paper by Robinson and Reiners (1999) was mentioned that includes a handy table with quite a few cultivars that have been analyzed regarding their ability to set parthenocarpic fruit. You probably know it already, but here it is for completeness:
Robinson, R. W. and Reiners, S. (1999): Parthenocarpy in Summer Squash. HortSience 34(4): 715–717.
https://journals.ashs.org/downloadpdf/journals/hortsci/34/4/article-p715.pdf (https://journals.ashs.org/downloadpdf/journals/hortsci/34/4/article-p715.pdf)
Unfortunately, I think that all commercial efforts in squash have focused on hybirds for a long time. So no commercial seed growers have made any effort to maintain OP populations unless they have been demonstrated to be useful for hybridization.
So maintaining OP squash varieties depends on amateur efforts, and not enough effort has been put in to keep all varieties cleaned up.
Quote from: Klaus Brugger on 2023-04-06, 04:38:11 AMThere's a thread (https://www.facebook.com/groups/950816328591402/posts/1645230525816642) in the Heirloom Cucurbits FB group about parthenocarpic squash. There a paper by Robinson and Reiners (1999) was mentioned that includes a handy table with quite a few cultivars that have been analyzed regarding their ability to set parthenocarpic fruit. You probably know it already, but here it is for completeness:
Robinson, R. W. and Reiners, S. (1999): Parthenocarpy in Summer Squash. HortSience 34(4): 715–717.
https://journals.ashs.org/downloadpdf/journals/hortsci/34/4/article-p715.pdf (https://journals.ashs.org/downloadpdf/journals/hortsci/34/4/article-p715.pdf)
The good news is that I'm also on this Facebook group. I'll ask around to see if any members know of any true to seed parthenocarpic squash varieties that I can use for breeding.
Besides increasing the number of female flowers, the goal of parthenocarpy is also to provide a reliable fruit set under otherwise poor conditions for pollination such as in very hot Summers or areas that lack squash bees. Another added benefit for this trait is that it would theoretically make growing squash under bug netting feasible for commercial market gardeners since the fruits shouldn't need pollination to form fruit. I've seen some varieties of squash marketed as parthenocarpic but when someone tries to grow such verieties the fruits end up tiny.