The limits of undirected selection

[ThomasPicard]

@MalcolmS

Maybe another issue is that taste could in theory be a very polygenic trait, and that in an unstable grex of an outcrossing species this makes any progress in the right direction very slow? Presumably many of your “best of the best” seeds actually represented a natural cross between “best of the best” plants and merely “good” plants, and similarly with the “good” ones?

@malterod

This was my thoughts too. So patience could be a friend.

@JesseI

I was thinking if the variance is bigger than the difference between different populations and so it’s hard distinguish if selection has moved the needle any way. Like if you can select average 5% improvement it would be very hard to notice without measuring brix from every fruit. I would just hold the course and keep favouring those with best taste.

It’s where it’s both a reflexion of our understandings and personnalities, and we can offer new intuitions or understandings or questions to others :

here is the synthesis or interpretation I made in 2024 from Joseph’s way of selecting allogamous like squash or melon over the years + my strategy which was relative to super diverse grexes with a hundred varieties of watermelon and melons for example.

That is :

• 2 years of crossings and zero selection (year 1 = AN 1 and year 2 = AN 2), so to say the “grex” stage
• then three year of taste selection, for me starting in 2024 (AN 3),
• and eventually the “maintenance” stage Joseph is talking about, with from then on a super gentle selection to maintain the qualities selected + marginal addition of nice varieties (1-2% of plants per year)

As I had big wide grexes in a climate where all varieties were fruiting (nothing compared to Utah!) I felt that the high potential of those grexes was all in the inner diversity which I didn’t want to loose too much in the selection process (that reflexion was mostly inspired by Cecarelli’s chapter on philosophies regarding assembling of evolutionary populations, a.k.a. modern landraces, and specifically by the 2nd philosophy outlined page 79 as I intend to bring my crops to new agroecological frontiers, that I won’t delve into here). So I decided to go through a rather slow selection process : trying to maintain some diversity at each step.

So that was my context and mindset. But as the outlined strategy (getting rid of the “so-so” at year 3 harvest , ofthe “average” at year 4 harvest, and then of the “good” at year 5 harvest, then maintaining excellence from year 6 on…) was purely based on my own synthesis and theorizing, I had to assess the result of that strategy. The 2025 melon and watermelon deployment of those different qualities in different plots was the occasion for that.

And so to build on my experience and trying to reply to your remarks, my understanding right now is that :

• the harvest criterias are crucial to make any progress in selection (talking particularly for places where the growing season is long! Where frost isn’t a selection factor!). An hour long video of Agrobio Perigord details a decade long zero progress in participatory selection of corn… despite tens of thousands of Euros in it (employees helping) + thousands hours of voluntary work by farmers… due to a lack of focus, lack of understanding of heredity, too much criterias in selection, lack of methodology… But essentially : subjectivity in the field! They were looking for too many things at the same time… So now they are focusing on just one or 2 objective criterias and they measure their progresses… eventually!

Harvest criterias are also of particular importance if you want to share your seeds to others : for ex I’m a very excellent harvester of watermelons with the “sound method”, so my selection was consistent with that, but when it went to farmers places in 2025 (about 6 farms) they were incapable of reproducing my “feeling” with the sound… So I had to go back to a more objective criteria (= opposite tendril must be dry), and ALL my selection will be coherent with that trait from now on. Same story for full-slip / half-slip / no slip harvest indications in melons in my very (too?) wide melon grex which encompasses about everything in the huge cucumis melo genome - much bigger and more complex than watermelon : only one type of watermelon against 7 to 9 types in melon!

So as my 2024 harvest wasn’t strict on simple objective criterias, and adding to that because there was so much diversity in those mixes, there was a first reason for that mess in the fields in 2025… Despite tens of hour of - what I thought was - “selection” in 2024!!!

• Complementary understanding from that 2025 years of selection is that, even if it was nice in theory to do a relatively slow selection, to stay coherent with new agroecological qualities I envisionned, in practise there could be too much of a dilution effect regarding fruit quality, that due to the fact that, as most of us doing selection with the fruit of an outcrossing plant, the outstanding fruit quality we keep seeds from is diluted proportionnaly to the “crap” of the surrounding plants. Meaning, in my case, and for melons especially as it appeared to be sssso inconsistent : I’ll be increasing the selection pressure drastically in 2026!!! And also to be fair I should add that, still for melon, the dilution of quality, due to an initial lack of understanding of what I was doing and consequentially of smart selection in first years, maybe too advanced! Next year will tell : either it’s too advanced (and so I’ll throw away all my melon seeds! bye bye melons…) or I measure progresses, and so I will keep on selecting with clearer and more objective harvest and taste criterias. And that shoud do.

For melons in 2026, I’ll strictly plant full-slip types (and so full-slip will also be THE harvesting criteria), and will plant only “excellent” melon seeds of the 2025 selection. I cannot do more with what I have : I won’t risk any “dilution effect” any longer. Then I’ll do a double taste evaluation with a brix minimum threshold + a secondary taste evaluation for complex aromas that no tool can tell, and only those superior types should be replanted in 2027.

In watermelons it’s less of a problem as - even if I didn’t make any progress in 2025 - overall quality is good to very good. And yields are there too. Did yields comparable to better than Sugar Baby in most cases (even in farms in complete different soils and climates).

In moschata and maxima taste selection in 2 months from now will tell.

Finally : I agree with @MalcolmS overall view on the topic : I’ve seen more and more vigor in my populations over the years, which is probably due to my intense oversowing and culling of 95% on early vigor over 3 years (anyone can check his/her supplementary vigor by simply growing "new varieties” on the side of his/her population), but in my experience there is still a fair amount of work on taste selection to get something consistent out of that first emerging trait. And that is more or less crucial depending on species and personnal objectives.

Objective harvest and taste criteria + selection pressure adapted to the consistency observed in the population, seems to me as the base formula of taste selection when dealing with our populations.

I hope that “dilution effect” is not a fiction - as I never heard of such thing ! - but it’s how I see the risk associated with wide grexes and/or too weak taste selection pressure in allogamous.