Roguing to ensure high quality seeds

It's gone time I should have done my first roguing on my cowpeas, but I find it just so darn difficult.

One of my big problems is that cowpeas don't grow this far north.  The first year I tried, they all died.  Last year, I tried again, four or five survived so I saved seeds from them.  Now, this year, I have three short rows of rams head cowpeas (also known as pretzel beans).  They are growing too close together so I need to thin them out anyway.  Once I've done that, I can stick some mulch down and with any luck, they will need less water.

Why rogue?  Sometimes some of the plants just aren't up to scratch.  If we let them produce seed, then saved the seed, our line of seeds could deteriorate.  Roguing helps keep the variety strong.  

How to choose which plants to rogue?  If we are maintaining a variety, then we can find the breed standard and kill any plants that don't conform to the requirements.  Or we can weed out the weaklings.  

In my case, I don't know which of these plants are stronger.  Most of them are the same height, so I guess I can cut out any that are less than 50% that height.  Some have dark green leaves, some light.  Some bug damage.  Some have shiny leaves, some not.  What are cowpeas suppose to be like?  Which ones are thriving in my conditions and which ones need to go?


this is the photo from the person I got the beans from.

I'm curious about my beans, but I would also like to make this a thread where people can ask questions about roguing or just chat about it.

One thing I'd look for are any that seem to be attracting pests more than others, this indicates they're stressed so less likely to be suitable for your growing conditions.

Will have to be making some of these decisions soon as well.  Garden went in late, but was out of the gate like a racehorse this year.  After reaching a stage of abundant foliar growth, some worrisome developments in disease progression.  In the past, the heavy artillery would come out in fungicide use, but that would be expected to mask any disease resistance or tolerance that would have been beneficial at this point.  So this year, we will probably just wait and see how bad the diseases get,.....and remove as much diseased matter by hand as possible.  The top photo is of probably Septoria on tomatoes (left) and Cercospora on Swiss chard (right).  Below that is blight on potatoes (most likely early blight with these symptoms) and possible Goss' wilt on the heirloom sweet corn (top and bottom panels, diseased and healthy leaves, respectively).

Seems like a good year to make some selective cuts in what gets saved.  I'm always inclined to save a few seeds from even highly-diseased plants:  It's known that in certain cases a gene for resistance to one disease is actually a susceptibility gene for a different disease.  So even at the risk of having an Achilles' heel in the garden each year, it may be wise to keep a bit of seed around for that purpose.  It will be interesting to get additional views on this.

I do a tremendous amount of culling... My criteria varies all over the place, but I'll give some examples...

Watermelon: Some years ago, we gathered together hundreds of varieties of watermelon, and let them cross pollinate. We included some wild watermelons in the mix.... So we picked up two undesirable traits. First was that some of the seeds were "hard". That means they didn't absorb water and germinate with the rest of the crops. Culling for that trait was as easy as going through the patch about a month later, and culling any plants that had just germinated. "As easy as..." Sheesh. There are so many things going on in a garden, it's not always easy to catch things at the right time to cull. But eventually I mostly got it right a couple years in a row, and the hard-seed trait went away. The other wild trait we picked up from the wild melons was "exploding melons". Basically, the rind was so thin that the melons  would get ripe and burst before we could pick them. Eliminating that trait meant not saving seeds from any melon that had exploded. It was harder to eliminate than the hard-seed trait, because by the time a melon is exploding, it has already shed it's pollen into the patch.

Muskmelons: The first few years I grew muskmelons, the most important trait was survival-of-the-fittest. They had to make seeds in my garden. Then that changed to earliness of fruiting. These days I cull a few slow growing plants, but the highest priority selection factor these days is amazing taste.

Corn: Vigorous growth of corn plants seems critical in my short season. It seems important to get the cobs high enough off the ground to prevent predation by mammals and birds. So I often go through the patch and cull corn plants that are growing much more slowly than the rest.

Here's an example of culling based only on the size of the plants. I don't remember if I took both of the slow growing plants or if I left the stronger of the two.


This corn plant was culled for what I thought of as a genetic defect. It lacked sufficient chlorophyll in it's leaves. There were a number of plants from the same parent with the same trait.


Squash: There might be times, when I don't cull a plant, even if it is growing slowly, especially if it has a trait that I'd like to explore... For example this squash has leaves like I have never seen before among it's species, or any squash species... I wonder if it's an inter-species hybrid? I liked this plant so much, that I culled the robustly growing, healthy plants next to it, to give it plenty of space to grow and develop. Especially in squash, I pay a lot of attention to keeping plants that are different than their peers. I value different leaf shapes/colors, and different colors/shapes of fruits, and different types of vines.  All things being equal, I tend to keep the things in my squash that are different from their peers, even if it means I am selecting slightly less productive plants. I found one moschata squash plant this year that looks like the mother might have been pollinated by Curcurbita palmata last growing season. It's a keeper. Photo to follow.  I didn't cull another squash plant with very odd leaves. It is growing very slowly. It's well on it's way to self-eliminating.

Odd type of squash. Definitely keep this one since it might be an inter-species hybrid.  


Beans: I don't do much culling on beans. I figure that those that succumb to disease, or to lodging are mostly self-eliminating anyway. And those that produce the most seeds are well on their way to dominating the population. That could be detrimental, if I were selecting for plants that produce lots of small seeds instead of fewer/larger seeds. Not that small seeded beans are undesirable... It's just a choice: People like their large beans, even if it means that they get less total yield.  I cull the bean patch to keep the plants mostly growing as bush beans instead of pole beans, but other than that, I tend to  leave them alone.

For the first few years after I start developing a new landrace, I tend to keep culling to a minimum. I am mostly interested in survival-of-the-fittest culling. Let whatever can produce a seed here go ahead and do it, and hopefully it will cross pollinate as much as possible with other plants that might be able to produce pollen here, even if they can't produce a seed. Then after a few years, I start selecting more heavily for production. Then once I get a variety that does really well here, I might not cull much any more...

John Weiland wrote:I'm always inclined to save a few seeds from even highly-diseased plants:  It's known that in certain cases a gene for resistance to one disease is actually a susceptibility gene for a different disease.  So even at the risk of having an Achilles' heel in the garden each year, it may be wise to keep a bit of seed around for that purpose.

Raul Robinson, in "Return To Resistance", recommends to start saving seeds from plants that are riddled with disease, and not from healthy plants. His reasoning is that the plants were healthy enough to produce seeds, and their resistance is likely due to many small synergistic traits rather than to one super-gene that will eventually be overcome by the pest or disease.

As ususal, Joseph, great insights on seed saving and what to look for one's various crops along the improvement programs.  Even with the rind so thin, what causes the melon to explode....is it just the water pressure inside?   I don't know much about that physiology...as the melon sweetens, does that result in osmotic swelling?

With regard to "His reasoning is that the plants were healthy enough to produce seeds, and their resistance is likely due to many small synergistic traits rather than to one super-gene that will eventually be overcome by the pest or disease."

I'm chuckling a bit because, in a sort of sick way, I'm thinking that could work for 'cold tolerance' as well:  If  plant papayas in northern Minnesota, there's that possibility that the cosmos will smile upon me and grant me a few plants with juuuuuuust the right synergy of traits to produce the first dwarfed, papaya row-crop harvestable by combine....     But to be sure, Robinson would have been selecting for the many factors that combine to provide horizontal resistance.  Unfortunately, there would be an assumption that the already-resistant parent material at the start of the project was resistant due to presence of a super-gene for that effect.....and there's no way of knowing that for sure without some molecular or pedigree testing having been done in the background.  And even if the gene does become defeated by the disease-causing organism, there is evidence that the concept of "defeat" is a quantitative one.....that if the gene is 90% defeated, then there is still a 10% resistance contribution.  In that case, this 10% combines with the other factors in Robinson's selection scheme to provide, down the road, the horizontal resistance that is more durable over time.  So I wouldn't exclude that highly-resistant parent material, but there would be a case for maybe keeping it separate:  With that high resistance present, other genes that normally would have to step up to the plate to assist in resistance against that disease might go un- or underdeveloped in subsequent generations.  So having both populations advancing along...if resources allow...may be the most prudent strategy of all.


And see:

Mol Gen Genet. 1999 Feb;261(1):58-63.

A "defeated" rice resistance gene acts as a QTL against a virulent strain of Xanthomonas oryzae pv. oryzae.

Abstract

The genetic components responsible for qualitative and quantitative resistance of rice plants to three strains (CR4, CXO8, and CR6) of Xanthomonas oryzae pv. oryzae (Xoo) were investigated using a set of 315 recombinant inbred lines (RILs) from the cross Lemont (japonica) x Teqing (indica) and a complete linkage map with 182 well distributed RFLP markers. We mapped a major gene (Xa4) and ten quantitative trait loci (QTLs) which were largely responsible for segregation of the resistance phenotype in the RILs. The Teqing allele at the Xa4 locus, Xa4T, acted as a dominant resistance gene against CR4 and CXO8. The breakdown of Xa4T-associated resistance mediated by the mutant allele at the avrXa4 locus in the virulent strain CR6 results from significant changes in both gene action (lose of dominance) and the magnitude of gene effect (approximately 50% reduction). Nevertheless, Xa4T still acted as a recessive QTL with a significant residual effect against CR6. The mutant alleles at the avrXa4 locus in CXO8 and CR6 that lead to a reduction in effect, or "breakdown", of Xa4T were apparently accompanied by corresponding penalties for their fitness. The quantitative component of resistance to Xoo in the RILs was largely due to a number of resistance QTLs. Most resistance QTLs mapped to genomic locations where major resistance genes and/or QTLs for resistance to Xoo, blast and sheath blight were identified in the same cross. Most QTLs showed consistent levels of resistance against all three Xoo strains. **Our results suggest that a high level of durable resistance to Xoo may be achieved by the cumulative effects of multiple QTLs, including the residual effects of "defeated" major resistance genes.**

(my asterisks added)

I get splitting muskmelons sometimes from irrigating... They don't explode, so much as just split apart. With the muskmelons, the green flesh has some structural integrity that the ripe fruit is lacking.

The exploding watermelons seemed to be due to getting warm in the sun... I wonder if  they had a bit of air inside the fruit, that built up pressure when the sun shone on the fruit. It was common for them to shatter apart during harvest...

John: Thanks for additional details about QTL resistance to diseases. I think another reason for choosing to breed with plants that show signs of disease, is that you can be sure that the plant was exposed to the disease. If you select from an unblemished plant, you can't know if it's because it is resistant, or if it's because it didn't get exposed.

Joseph Lofthouse wrote:
The exploding watermelons seemed to be due to getting warm in the sun...

Around here, they put hay mulch *over* the melons to stop them exploding.

I just got back from my garden to harvest my tomatoes and I thought of this thread.

I plant two OP heirloom tomato varieties every year because they are early, productive and very tasty. I usually plant them in my side garden and they get about 4ft tall and are pretty productive. I have some black spot and had whiteflies one year, but the plants didn't seem to care or be bothered.

This year I grew them in the back garden, which has a lot more disease pressure, notably verticillium wilt. I've noticed a degree of tolerance in some of the many varieties I have trialed in the back garden, but have never planted my two staple tomatoes in the back garden.

The plants grew to 6-7ft tall, fell over (I can't seem to stake tomatoes well), got black spot, got verticillium wilt, and possibly late blight. I watered way less than I should have, barely weeded and pretty much neglected my tomatoes very badly. The wilt caused the fruit to be in full sun and gave them sun scald.

Even with all the problems, I just got done harvesting about 50 lbs of tomatoes from 5 very sickly plants. This is my third time harvesting, and I'd say I have harvested close to 100 lbs of tomatoes with no cides, fertilizer, or anything other than our homemade compost and some grass clippings from our lawn.

Despite the insane disease pressure, my tomatoes still did amazing and although my tomato season is done thanks to verticillium and late blight, I have to say I am really happy with them. Even though they aren't resistant or tolerate all the disease pressure, I'm still going to save seed from every one of those 5 plants and try and breed some verticillium and late blight resistance into them. I want to develop a landrace with these varieties because of the fact that they are so productive despite total neglect and attack. I'm dreaming of how they would produce if they had resistance and lasted all summer.

@Thomas Z.: "... I just got done harvesting about 50 lbs of tomatoes from 5 very sickly plants....Despite the insane disease pressure, my tomatoes still did amazing and although my tomato season is done thanks to verticillium and late blight...."

Kind of a contrary observation, but it's been noted with tomatoes how certain diseases can accelerate ripening of the fruit.   Like you indicated, if you get what you need, it's all good in the end and one can tolerate a certain amount of disease pressure.  The data indicate that there is indeed some sacrifice of yield with these diseases, but there are years when I'm appreciative that the Septoria leaf spot actually sped up the harvest period, even at the expense of a bit of yield.

I allow a few tomatoes, squash, etc. to rot on the vine and re-seed themselves and look for volunteers the next year.   If I do get a volunteer, I mark that plant as one that for seed collection.  

I assume any plant that volunteers as being naturalized to my area or on the path towards naturalization.   I used to seed barley in the fall as a cover crop.   I collected the seeds for the fall crop from the spring's harvest.   One year, a family emergency called me away when the barley was ready to harvest.   When I came back, the barley had already shattered and was on the ground.   That fall I noticed barley coming up, and the following April I had a crop.   Being lazy, I let the barley shatter and scatter.   Since then, the barley that grows has grown thicker and sturdier every year.   I think this is because the barley best suited to my climate is what survives to seed again.

So now I try to give each of my plants a chance to volunteer.   Except for heavy mulching in the fall because of my cold climate, I offer no other aid.   I had 1 volunteer tomato, a mystery squash volunteer, and a large number of cabbages volunteered.   Too soon to say if I have naturalized plants to my location, but I made sure that envelopes containing seeds from these volunteers are marked so that I can track them next year.