Hybrid Vigor

General Discussions
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I’m interested in this topic, and I think my interest tends towards being able to come up with an appropriate definition of productivity for landrace gardening so that it can be compared in those terms to the vigor and productivity of conventional F1 hybrids. I am currently reading One Straw Revolution for the first time, and I’m sure Fukuoka is influencing my thoughts on framing.

In terms of the academic literature, at some point I am pretty sure I had access to the full text of the chapter I’m linking below, but at the moment I don’t seem to be able to access it. In my recollection, it speaks to this, but I am hoping that you all might have credentials where you can pull up the whole thing. If not, I can see if I can find someone at an institution who can access this on my behalf.

Edit: If I recall correctly, what they are referring to as “participatory plant breeding” is participatory breeding with “evolutionary populations”, which is akin to landrace gardening.

Here’s the abstract:

Despite its demonstrated efficiency, participatory plant breeding (PPB) has not gained widespread acceptance. Selection theory and variety adoption dynamics provide the scientific basis of PPB. Decentralized selection (selection in the target environment) yields greater genetic gains, particularly with heterogeneous target populations, as is common in marginal environments. Moreover, when the efficiency of a plant breeding programme is measured by both the genetic gain and by a measure of adoption, PPB has been shown to increase the probability of adoption, biodiversity and hence nutritional quality; it also has a higher benefit/cost ratio than non-participatory breeding. However, PPB has failed to gain favour even in institutions working to reduce poverty and malnutrition, promote improved livelihoods and assist marginal farmers. Its wider adoption has been hindered by reluctance to accept the implicit paradigm shift regarding seed sovereignty and food sovereignty. We propose evolutionary participatory plant breeding (EPPB) as an alternative: it has many of the advantages of PPB, but is more effective in bringing back diversity in farmers’ fields without necessarily requiring the support of a scientific institution.

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it would be super helpful if you could make a little screenshare summary explaining this graph

Rather than a screenshare I’ll just drop this simplified version of the same graph. It should be much more self-explanatory.

wheat
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The purpose of this graph is to demonstrate a technique called PCA; the goal of it is mostly just to suss out behavioral trends. Given all of the data they collected: plant height, plant temperature, time to maturity, yield, spike number, etc … can we create broad groupings or predictions about the behaviors of the plants? Do some traits imply or predict other traits? PCA can take all of these variables and try to ‘compress’ them down based on the assumption that traits are sometimes likely to be correlated. Because we can’t very easily visualize a 8-dimensional graph.

As you see, there is a distinct separation between the modern cultivars (blue) and the landraces (orange). There’s also a distinct separation between the ‘Arid, Low Irrigation’ environment, all of those squares bunched up on the left hand side. The gulf between modern cultivars and landraces was narrowed in that stressful environment. But overall the modern cultivars still yielded more, even then.

The study found that thousand kernel weight (TKW) and yield (GY) were highly correlated, which is what the red arrows on the original picture are suggesting (they point in about the same direction, toward the modern varieties). Plant height and time to maturity (GDDtH and PH) were more associated with landraces, the arrows pointing to the bottom right corner. Higher temperatures (CT) generally meant fewer plant spikes, less spike weight, and less dry matter (SPN, SpW,DM_M), so those arrows are pointing in opposite directions. The fact that temperature arrow is pointing directly into the low-irrigation arid environment shows that intuitively. The Coastal High Irrigation environment (down triangles) had lower temperatures and higher dry matter/spike measurements.

I looked into what these ‘modern varieties’ actually are and I couldn’t find hardly any information about them online. I did find that one of them is a GMO variety. I couldn’t find exact information about the farms where these were grown, but based on the naming conventions they appear to be roughly west of Jerusalem.

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Yes, I also read that when it was freely available, not sure why they decided to limit access! But you can request a copy from the authors here: https://www.researchgate.net/publication/336233377_From_participatory_to_evolutionary_plant_breeding
If I recall correctly, they went through a whole explanation of why it was a great thing for grains and then said it couldn’t work for vegetables … huh? (or maybe that was another article).

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I have used this research review as a source for the wikipedia article on plant breeding. It speaks to the question of how to define the potential advantages of diverse crops in order to compare to conventional cultivars.

Decentralized-Participatory Plant Breeding: Adapting Crops to Environments and Clients

…two causes of the controversy are the range of environmental variation sampled and the type of genetic (or breeding) material being used, and most of the studies comparing the two strategies are biased either because they use a narrow range of environments, or because breeding material selected for specific adaptation is not included.

Breeding for specific adaptation is particularly important in the case of cropspredominantly grown in unfavorable conditions, because unfavorable environments tend to be more different from each other than favorable environments (Ceccarelli and Grando, 1997)… Breeding for specific adaptation to unfavorable conditions is often considered an undesirable breeding objective because it is usually associated with a reduction of potential yield under favorable conditions.
This issue has to be considered in its social dimension and in relation to the difference between adaptation over space vs. adaptation over time: for example Australian farmers prefer maximizing yield in favorable years, while for North African and Near East farmers yield in very poor years is more important.

However, the most serious limitation of decentralized selection for specific adaptation to unfavorable environments is in the large number of potential target environments. Moreover, the number of target environments increases if we consider that environment is not only climate, soil, agronomic practices, farming system, etc., but also people leaving in that physical environment, their perception of risk associated with yield variation over time, their usesof the crop, and the consequent importance of quality traits even if neutral in terms of adaptation to the physical environment. Clearly, selection for specific adaptation to unfavorable conditions needs a larger sample of selection environments than selection for favorable environments

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edit: posted in the wrong place by mistake

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How Do Older Wheat Cultivars Compare to Modern Wheat Cultivars Currently on the Market in South Africa?

Bread wheat is cultivated globally and is currently the major staple crop in temperate zones. After maize, wheat is the most important grain crop, cultivated in South Africa. ‘Ancient’ wheat landraces were cultivated commonly in the past, but are today only grown on a small area in some countries for traditional foods. Because they have been proposed to be rich sources of bioactive components these historical wheat landraces, compared to current wheat cultivars on the market, are believed to produce higher value food products with enhanced health benefits. In South Africa there has been a renewed interest in older wheat cultivars, such as Witwol, by farmers producing wheat for niche markets. Bolane and Makaloate are cultivars planted traditionally in the highlands of Lesotho. To determine how these older and traditional cultivars compare with modern wheat cultivars on the market, Witwol, Bolane and Makaloate were compared to dry land wheat cultivars, currently on the market in South Africa, with regard to Russian Wheat Aphid (RWA) resistance, yield, hectolitre mass, protein content, mixing time and loaf volume. Since these ‘heritage’ and traditional wheat cultivars are low yielding in comparison with modern wheat cultivars on the market and not adapted to modern agricultural practices, they will not contribute to feeding the growing world population, but the re-introduction to the market and use of ‘heritage’ and traditional wheat cultivars might have a place in markets where its holistic use as crop is a viable option for producers, millers and bakers who cater for specific consumer markets. Encouraging the cultivation of these cultivars will also increase the biodiversity of our food products.

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Agronomic and Kernel Compositional Traits of Blue Maize Landraces from the Southwestern United States

Diverse landraces of maize have been cultivated for centuries in the southwestern United States and northern Mexico primarily for human food consumption. A striking feature of these landraces is the wide array of kernel colors displayed. Traditional cultivation is declining, but blue maize has received increasing commercial interest due to rising consumer demand for unique food products with health benefits and special culinary uses. We evaluated grain yield, agronomic and morphological traits, and analyzed the kernel biochemical composition of five blue and one purple landraces representative of diversity in the Southwest. These were compared with selected open-pollinated populations derived from Southwest and Corn Belt blue maize at several New Mexico locations in 2012 and 2013. Kernel amino acids, oil, protein, starch, fatty acids, crude fiber, ash and anthocyanin pigment contents were determined. Grain yield across all locations, years, and accessions averaged 2.11 Mg ha−1. Navajo Blue and Hopi Blue were the highest and lowest yielding accessions, respectively. The majority of southwestern landraces displayed higher oil content, and two displayed higher protein content, than the Corn Belt Dent variety. Little variation in total amino acid content was observed. Several southwestern floury accessions displayed ∼10% greater lysine and methionine than did dent or flint genotypes. Considerable variation for plant, ear, and kernel compositional traits within and across southwestern landraces was consistent with the presence of racial admixtures. The health-promoting properties of anthocyanin-rich landraces contribute to sound dietary nutrition and human health. This study further illustrates the diversity of southwestern maize and supports the rationale for their continued conservation through sustained cultivation and utilization. Directed selection to improve grain yield and uniformity will be necessary to enhance their potential for commercial production.

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Landrace Germplasm for Improving Yield and Abiotic Stress Adaptation

Note: I haven’t gotten a copy of this text yet, but I am pretty sure it is relevant to this topic. Probably someone at ttps://www.reddit.com/r/Scholar/ will run off a PDF of this if asked

Plant landraces represent heterogeneous, local adaptations of domesticated species, and thereby provide genetic resources that meet current and new challenges for farming in stressful environments. These local ecotypes can show variable phenology and low-to-moderate edible yield, but are often highly nutritious. The main contributions of landraces to plant breeding have been traits for more efficient nutrient uptake and utilization, as well as useful genes for adaptation to stressful environments such as water stress, salinity, and high temperatures. We propose that a systematic landrace evaluation may define patterns of diversity, which will facilitate identifying alleles for enhancing yield and abiotic stress adaptation, thus raising the productivity and stability of staple crops in vulnerable environments.

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Reactivating this old thread to suggest a possible solution to the question of why hybrids might yield more than a local landrace.

We’ll assume that hybrid vigor is mostly due to the dominance hypothesis; ie, that it is simply the opposite of inbreeding depression. Populations of plants accumulate deleterious recessive mutations over time; a plant that is homozygous for such a mutation will have lower vigor, while one that is heterozygous will have normal vigor. Inbreeding leads to the fixation of these deleterious mutations, while hybridization/outcrossing yields plants that are heterozygous and therefore more vigorous. (Leaving aside any other effects of breeding such as selection for higher yield, etc.)

With this as the background, I think we can see why landraces, even ones which are genetically diverse (as someone noted above, some landraces in these studies may actually be inbred) might have a lower average vigor when compared to hybrids under standard farming conditions. In a hybrid line, every plant is completely heterozygous. By contrast, in any given generation of a landrace a certain percentage of plants will be homozygous for deleterious recessive mutations, simply due to the nature of genetics (the basic idea behind a Punnett square.)

In a home garden, such plants can be eliminated by planting twice as many plants as needed and thinning out the weaker ones. But under standard farming conditions, I’m guessing this is difficult or impossible to achieve. And so, under standard farm conditions (anything over a few acres) hybrid plants will preform better, because their average isn’t pulled down by the inevitable weaker plants produced by a hybrid.

In a small garden/small farm where plants can be individually thinned, a landrace might actually yield better than a hybrid, because weaker plants could be removed and the other advantages of a landrace would still be in effect. Even on a larger farm, landraces might prove more resilient, and will continuously adapt to changing conditions, which is a large advantage and might make losing some yield worth it. But the larger the farm, the harder selection will be to perform, both when it comes to selecting individual plants and when it comes to shaping the whole genepool.

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I’m not a farmer, simply a backyard gardener. So take my thoughts with a grain of salt.

It seems likely to me that farmers could probably plant extra landrace seeds, just like gardeners do, and get just as much of a harvest as from hybrid seeds. The larger number of seeds used would be offset by the fact that they wouldn’t have to pay for new seeds every year.

That said, diversity in traits like high or ripening times might be highly undesirable to a farmer and cause a lot of extra work.

That said, a local landrace can be bred to select for uniformity in the traits that matter to the individual grower, so I would think this issue could be settled quite easily just by saving seeds only from the ones that are most what the grower wants to achieve.

And of course, this is what farmers have presumably been doing for thousands of years . . . so it seems logical to me?

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I’m also a gardener, not a farmer, though some of my gardens have been rather large.

And I agree; small farmers have been growing landrace crops forever! But they’ve tended to be getting lower yields per square foot than they would if they were growing a well-suited hybrid; my thought on this, as described above, is that any landrace will inevitably produce a certain percentage of inferior plants every year, which will drag the average production value down . . . unless they are thinned out.

As to why farmers can’t just plant extra; they could. The problem would be thinning, which can’t be mechanized, since the goals is to pick the superior plants. And thining for superiority is harder with some plants than others.

For instance; I probably thinned out 30 broccoli plants for every one I finally left. I planted thickly, and removed half the plants in the seedling stage, selecting for vigor. Then I removed more a few weeks later, again selecting for vigor and aphid resistance. And finally, I culled out plants that “buttoned” and produced a small head too early. I could do that because I had a hundred square feet of broccoli. If I hadn’t thinned, I wouldn’t have got any broccoli because they would have been too crowded to produce well; as it was, I got behind and probably stunted things a bit.

And broccoli is an easy crop! Let’s imagine thousand acre wheat field; no way anyone is going to be hand thinning that and selecting for the best plants. Somebody could hand-select a few hundred square feet for genetic improvement, and then plant that seed on a larger area; but they won’t have been able to remove invisible damaging recessives, and so when planted out in the larger field, a certain percentage of plants won’t be as productive. By contrast, with hybrids, none of the plants will be homogeneous for a damaging recessive.

I’m not arguing that we should grow hybrids instead of landraces, since landraces are more adaptive, easier to produce for oneself, and have other advantages. But my thinking, backed up by the studies discussed above, is that landraces will probably always be a little lower yielding . . . except in small plots of a couple of acres or less, in which the inevitable inferior plants can be removed rather than allowed to take up space for the whole season.

And since I would advocate for more food production at “garden scale” (a couple of acres or less) that’s a conclusion that I’m OK with.

It is also possible that landrace plant breeders could do some type of mass line selection to remove lines carrying unwanted recessives, and then combine lines to maintain a high level of adaptive diversity. But that’s a pretty big investment of time and energy, probably something that would be done by just a few people on the village level for the benefit of the rest of the village.

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Ahhhh, I see what you mean. Yeah, I can see why thinning — because it requires making value judgments — would require a lot more hands-on time, most of it from the farmer themself, because it would be challenging to delegate and almost impossible to mechanize.

I really like your “village” approach. That seems like a fantastic long-term solution. It makes me think maybe that’s something subsistence farmers have been doing for ages.

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Farmers have a system that is optimized for the particular variety they grow. It makes sense that other varieties might not thrive in those conditions.

I see commercial farmers as more of an end-process contributor.

If a stabilized landrace produces, say, two thirds of the yield of a commercial crop, with no fertilizer, no patented seed, no fungicides or herbicides or pesticides, the difference might be workable. Without all the purchased inputs, a farmer might actually be able to make a profit.

The thinning and careful observation would be for the seed producer, not the large commercial farmer.

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I think the problem is that the current farming system is so dummed down. Not seeds, but how we farm. It’s not very effective in terms of yied per m2, but rather goal has been to make everything as effective in terms of time spent on m2. Even if land isn’t suitable for that type of farming it is still used as only averages matter. This was brought forth in one study and subsequent trial (that there was a documentary of) that they could (in Minnesota if I remember correctly) farm only 50% of the area used for corn at this moment and still get 90% of the yield. They used new scanning methods to see which parts of the fields reliably underperformed and thus would be better left to the nature. That’s a problem with any large scale farming no matter how you slice it. Landrace could, with thinning, do better in those worst performing spots, but is it worth it still? I would say we would need go back to smaller farm sizes with more consideration how to get maximum yield with as little damage to the land. I also think it wouldn’t be too expensive to do thinning in crops like squash, even manually. Like 10 seeds per m2 for 1-2 plants m2, how many seconds it would be per m2 to walk through with something like rubbish pickers to cut those extras? It would be just an extra step, and that’s what current farming system hates. Even if it would be beneficial.

Also slightly off topic (maybe). World record yield (per hectare, acre? not sure which) was set for rice in India with regenerative farming, without chemical fertilizer, without tilling (if I remember correctly) and with a lot less water. Someone had figured that we had gone the wrong way all along. Can’t remember if it was hybrid variety or local variety, but in any case it shows that farming has become more about playing with technology rather than farming and caring for the land. Not that technology can’t be good help, but those that build machines or sell the fertilizers shouldn’t be the ones deciding how land is farmed.

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Hi Jesse, yes, I think smaller farms are much more efficient at use of space (all else being equal).

And I agree, some crops would be much easier to thin manually (squash, corn, most vegetables)

The hardest would probably be wheat and other small grain crops. Each plant doesn’t yield that much, plantings are closely spaced, and at reasonable scales (anything beyond a garden plot) they are planted either broadcast or by drilling, neither of which are very conducive to overplanting and thinning. I can’t imagine anyone manually thinning even a few acre of grain (a very small field), at least in such a way as to reliably select the best plants.

Another factor is that some unwanted traits only show up late enough that thinning won’t eliminate them. For instance, in my broccoli landrace, there is an odd trait where plants just keep flowering and don’t set seed; it must be some sort of recessive, otherwise it would have been eliminated by now. With broccoli it isn’t a big deal, but with a crop where seed was the desired crop it would be a problem, and would only show up when it would be too late to thin it out and allow a more productive plant to use the space for the season.

One possible fix for some crops is to maintain an evolving landrace population, select some of the best plants every few years, do a couple of rounds of inbreeding/line selection on them, and use them to produce a bunch of local hybrids; you’d get hyperlocal adaption, community control of seed stock, and gain some of the benefits of hybrids, particularly avoiding double recessive plants.

(Edited to add; lines don’t have to be as inbred as they are commercially to produce reasonable quality hybrid crops, and we would also be able to produce such local hybrids without the use of pollen-sterile techniques by putting a bit more work into it.)

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Hi Lauren,

I agree that saving the cost of inputs can often make lower yields worth it. But some of the studies above seemed to show hybrids still outyielding landraces under low input conditions.

I think that with a landrace crop, thinning and careful observation would be needed by both the seed producer and the farmer, though with a slightly different purpose. For the seed producer, the purpose would be to improve and maintain the population. For the farmer, the purpose would be to remove the inevitable percentage of off-types (largely the carriers of double recessives) which any landrace will produce in each generation and which will pull down average production if left to take up space in the field.

Of course, if the farmer is OK with lower yields, they wouldn’t have to do this. But it makes sense that hybrids do have a real, biological advantage, even if that advantage has been overstated, confused with the yield boost caused by more inputs, and is larger when compared to inbred crops. If it wasn’t so, farmers and experimenters would never have started using hybrid crops with their greater costs in time and/or money.

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One thing to consider is that these hybrids are not just randomly crossed.

Both parent varieties are likely already very well adapted to the growing conditions and when crossed they produce offspring that have a combination of those different beneficial adaptations.

I’m not saying hybrid vigor is not contributing, just that “hybrid vigor” alone is not the only thing (or potentially even the main thing) leading to these increased yields.

It would be interesting to see the performance of a “grex” of many different and well adapted varieties, but all already expressing the uniform traits the farmer desired.

It would not be as genetically diverse as a true landrace, but it would likely be more resilient than most comercial varieties or hybrids.

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One thing to possibly consider is that not all farm-owners are actually interested in being farmers. Some are people who are independently wealthy who own farmland and have to produce something on it, anything at all, in order to use the land as a tax shelter. (I think this system is a bit of a problem because it prevents people who want to be farmers from being able to afford to buy that land and use it more effectively . . . but I disgress.) So they need something easy to grow that they can sell in bulk for a mild profit or even merely break-even, and that’s pretty much it.

There’s a difference between that kind of farm-owner, who will never be interested in landraces, and a farmer who really cares about making a profit and is willing to put time and effort into improving the land and the crops that grow on it.

Just a thought.