Exploring “Crazy” Watermelon Genetics

The other day there was an interesting discussion about watermelon genetics that started on the Alan Bishop Homegrown Goodness plant breeding forum from a fellow who lives in Australia. Turns out Watermelon genetics are sort-of complicated, but interesting.

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Approx. Watermelon Flesh Color Spectrum, from most dominant to most recessive.

The discussion started by asking about which traits in watermelon were dominant, mostly referring to flesh color but also open to other traits as well. The original poster mentioned that he started his own mass cross of over 30 watermelon varieties together (a grex) in preparation to developing his own landrace adapted watermelon to his Australian climate. He said this past season he planted only the seed for any F1 hybrids from any yellow fleshed watermelons he had but got about 90% red fleshed watermelons and concluded that obviously red-fleshed watermelons were dominant. The interesting thing is they are BOTH dominant AND recessive at the same time! Yes, watermelon genetics is a little complicated to say the least, lol.

Wait… what??!… haha yes, you did read that last sentence correctly. Red-fleshed watermelons are both dominant to yellow-fleshed watermelons AND recessive to yellow-fleshed watermelons. Turns out there are actually TWO different kinds of yellow-fleshed watermelons.

Watermelon Flesh colors range from various forms of red, pink, yellow, orange, and white. So how does one figure out what is recessive and/or dominant over what? Turns out most of these have already been studied and we can interpret that data. I’ve recently resurrected my old website domain and turned it into a plant breeding wiki of sorts. Feel free to check it out @ www.biolumo.com. The main resource i am using is the wonderful watermelon genetics info posted online by the Cucurbit Genetics Cooperative hosted by North Carolina State University and in particular Todd C. Wehner part of the Department of Horticultural Science at North Carolina State University. http://cuke.hort.ncsu.edu/cgc/cgcgenes/wmgenes/gene12wmelon.html

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From the data available we can come up with a rough basic pictorial based diagram. I like pictures; they help me understand things better. Basically there are at least two types of red-fleshed known as “Scarlet Red” and “Coral Red” in addition to two forms of yellow-fleshed known as “Canary Yellow” and “Salmon Yellow”. Turns out Canary Yellow is dominant to all other forms of color. Scarlet Red is dominant to Coral Red, Orange, and Salmon yellow. Coral Red is dominant to Orange and Salmon Yellow. Orange is dominant to Salmon Yellow. You get the point. And basically seems to work in a cascading effect of “more color” to “less color”.

I personally prefer the taste of the Canary Yellows over most red/pink, though there are still some good red ones out there! What i don’t like are the Salmon Yellows (and maybe orange). To me and in my climate the Salmon-Yellow watermelons have a weird mealy and/or mushy texture and have a muted / poor flavor. By contrast the Canary Yellows seem to be really sweet and might even get sweeter more easily / earlier in a northern and colder climate like mine. That is just my personal preference, your taste buds and soil conditions may differ.

Now this is a general simplified version. There are a few caveats however. Such as the fact that there is a Canary Yellow inhibitor gene that when present will turn a Canary Yellow back into a red that is hiding underneath. Also the fact that there may be a few other minor colors that have not been studied yet such as “dark red“, “rose” , and “pink“. It is possible that these colors are just minor variations of the former reds and function the same way from “more color” to “less color” in terms of dominance. It is also possible that if these are indeed separate shades of color that they may buck this trend and function in completely different ways from different biochemical pathways. Hard to say at this point. But i will leave the possibility open either way in case new studies in the future address these watermelon flesh colors.

Oh, and what about white-flesh?! Yes that’s right, we have completely forgotten to talk about white fleshed watermelons. Oh, you didn’t know there were white-fleshed watermelons? Yeah there are. They are not generally as common but there are white fleshed watermelons out there. Turns out white-fleshed is a little more weird. Let me explain.

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F2 Generation of White-Fleshed Watermelon Genetics

 

White-fleshed watermelons are currently being studied more in depth in China and a new paper is due any time in the near future. But until then all we have is the data gathered already from a past study on it. According to that study: white-flesh were found to be dominant over all color. In an F2 (Second Filial) Generation the ratio is: (12 white : 3 canary-yellow : 1 red).

Pretty interesting huh? Yeah, basically if i interpret this information correctly is that for whatever reason white flesh overrides color. In the wild, watermelons were originally thought to be white fleshed and low in sweetness. This is certainly the case in the wild citron melon (Citrullus lanatus var. citroides) which has hard white flesh and bland flavor. The bitter apple melon too (Citrullus colocynthis) but it obviously is very bitter.

The genetics for watermelon at this point captured my interest so i decided to find out what i could about seed coat colors. If you thought watermelon flesh genetics was complicated, you’ll find the genetics for watermelon seeds is a nightmare. Nevertheless i waded knee deep into the confusing data and came up with some generic info that i think can give us a basic trend that we can use.

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Approx. Watermelon Seed Coat Color Genetics

The genetics for watermelon seed colors and patterns is a nightmare. Truly it is. Partly because the studies we have don’t all agree and we don’t have examples of what these old researchers were really studying. One person’s “tan” might be another persons “light brown”, etc. You get the point. Very subjective. But based on the studies we have it basically looks like in general there are three genes working together and we can come up with a basic trend that we can follow.

Basically black seeds are dominant to other colors. Brownish or greyish seeds with a particular black mottling striping with black dots is next in line. Tan or brown seeds are probably next in line. Green seeds (not pictured here and rare) are dominant over red. Red seeds are the most recessive except for white. White seeds are the most recessive and recessive for all three gene combinations. This is a very simplified interpretation and there are probably actually more than three genes. In my population i have grey seeds which is not a color that has been studied. Also i have no idea what “tan” actually is so i lumped it in with brown. Brown too has not been studied, nor has “reddish-brown” among others.

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Watermelon Fruit Shape is Co-dominant. Elongate (OO), Oval (Oo), and Spherical (oo).

Watermelon Fruit shape is relatively simple however. Yay! Simple co-dominance at work. Two long genes (OO) give you long fruit. One long gene and one round gene (Oo) or heterozygous gene pairs give you medium oval shaped fruit. And two copies of the other round gene (oo) gives you round spherical fruit. Easy peasy!

Golden-rind fruit are easy genetics too. Simple recessive (go). This is a trait more common now as it helps people identify when a watermelon is ripe. They turn bright yellow when ripe.

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Yellow-rind fruit are recessive (go). Fruit become golden yellow as they mature.

And the last trait i will mention is the “explosive rind” trait.

Haha, it’s not as scary as it sounds, but it’s not particularly a trait you want in your watermelons. Fortunately it is recessive and hopefully you wont encounter it in many varieties. I’ve seen it in the unusual striped variety but fantastic tasting ‘Osh Kirgizia’ watermelon, but otherwise not that much. Officially explosive rind (e) causes the fruit rind to burst or split when cut. This is true, but i also find that often when this trait is present the fruits themselves have a higher rate of splitting open while ripening on the ground and even when you lightly grab one to harvest. Not a trait that a market grower would want. For a small backyard gardener it’s not a huge deal as you can eat them right away, but still a slight inconvenience, especially if they split in the field and ants get to them. Black ants really do love sweet watermelon flesh.

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The recessive explosive rind trait (e) causes watermelon fruit rind to burst or split

 

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Wild Galapagos Island Tomatoes and the Secrets of Diverse Wild Tomato Species

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Solanum Cheesmaniae, “the” Galapagos Island Tomato.

Like Corn (Maize) and it’s ancestor Teosinte, Tomatoes have wild relatives as well. And what a variety of species they have too! My love and interest in growing, observing, and breeding with these wild tomatoes, like tesosinte, is only continuing to grow.

The wild tomato that I learned about first, and led me down this path, was the almost mythical “Galapagos Island Tomato”. From the same famous islands visited by Charles Darwin in his expedition to catalog biological diversity in all it’s forms. And what better place to start learning about wild tomatoes than from the Galapagos Islands (Ecuador), an enchanting place steeped in biological diversity.

There are actually two main species of native Galapagos Island tomatoes, Solanum cheesmaniae and Solanum galapagense, and they are closely related. Originally, S. galapagense was thought to just be a subspecies of S. cheesmaniae, but was later discovered to be a separate species fairly recently by Sarah Darwin, the great great granddaughter of Charles Darwin. Interesting to see a family legacy of scientific inquiry passed down, but also somehow fitting.

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One form of Solanum cheesmaniae leaves and growth pattern.

Both forms are said to be quite salt tolerant (S. galapagense in particular) and may posses some disease resistance. But they also still retain many traits in common with domestic tomatoes and are easily crossbred with them. This salt tolerance is one reason why these tomatoes are so sought after for introgression into modern tomato varieties. Crops that can survive in the harshest of climates and that could be watered with sea water rather than the worlds increasingly limited supply of fresh water is one high area of worldwide interest.

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Solanum galapagense, small orange hairy fruits.

Both S. cheesmaniae and S. galapagense are very different in appearance and traits despite both originally thought to be the same species, though similar in many respects. I find the scent of S. cheesmaniae leaves to be of a mild lemony scent but with a strange overtone along with it. The smell of S. galapagense is much stronger with still a sort of lemony smell but a very pugent after odor as well. One person i talked to went to the extreme as saying it smelled like “burning garbage”. Haha, i wouldn’t go that far, but it is an odd smell indeed. Not exactly pleasant.

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one example of typical S. galapagense leaf shape and typical sickly yellow appearance.

S. galapagense is of particular interest because not only does it have salt tolerance as well (if not more so that S. cheesmaniae), but it also has unique pest resistance to the common whitefly, a major domestic tomato pest that can spread disease and decimate tomato crops. Solanum cheesmaniae however does not contain this resistance to whitefly, nor do many of the other wild tomato species either. And of those rare few accessions that do, S. galapagense beats them hands down. This is due in part by two factors. One is that it is densely covered in type IV glandular trichomes, or hairs, while simultaneously producing volatile acyl sugars which help repel insects. A sort of bug repellent and/or insecticide. Pretty cool, huh?

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Additionally S. galapagense is the more interesting species anyway, by way of genetic diversity and divergence from domestic tomato DNA / genomes. According to one study, that compared to the DNA of S. galapagense, S. cheesmanie, and domestic tomato S. lycopersicum, they found that S. cheesmaniae shares 71.5% of DNA markers with domestic tomatoes, while S. galapagense only shares 57.6% of it’s DNA markers with domestic tomatoes. With only of about 50% DNA markers being shared between S. cheesmaniae and S. galapagense.

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Distribution map for S. cheesmaniae and S. galapagense on the Galapagos Islands.

A map of the distribution of S. cheesmaniae and S. galapagense shows that S. galapagense is not present on the eastern islands. This has led to speculation and conflicting data about the origins of both species and evolutionary distribution on the islands. One study suggests a colonization from east to west , from older to younger islands, supported also by the fact that ocean currents average an east-west direction. If the colonization of Galapagos Islands was east to west, then S. cheesmaniae could be an older species than S. galapagense, and could even be an ancestor to it.

However, high diversity in the S. cheesmaniae group and its correlation with the islands of origin were also suggested. This indicates a possible influence of the movement of the islands, from west to east, on the gene flow, which is the opposite direction. And the lower genetic variation in S. cheesmaniae found in the older islands could possibly be due to a founder effect, and colonization could have happened from west to east. If this was the case, S. cheesmaniae and S. galapagense could have diverged around the same time from the same ancestor. So in short, while that is all fascinating speculation about whether S. cheesmaniae is descended from S. galapagense, or S. galapagense is descended from S. cheesmaniae, or whether they both diverged from a common ancestor we just don’t know. I personally am inclined to believe based on the evidence (until further studies come forth) that both diverged from a common ancestor and moved east to west. Older populations of S. galapagense could possibly have been eradicated on the eastern islands from continual volcanic eruptions and S. cheesmaniae could have been reintroduced onto the eastern islands by traveling animal species. We just don’t know.

One word of caution though if you decide to go looking for seeds for these Galapagos Island tomatoes. You almost certainly wont find pure S. cheesmaniae or pure S. galapagense seeds out there except direct from a seedbank. There are a LOT of snake oil salesmen out there that claim to have them, but while it is possible that they have some wild galapagos tomato heritage, these varieties are almost certainly not pure. Some may very well have S. cheesmaniae ancestry, but are not pure. I have yet to grow out many accessions of S. cheesmaniae and access the genetic diversity in the species, but one that set fruit this last season was about the size of about the nail of my ring finger. Super tiny. One way you can tell if they might be authentic is if the seeds themselves are incredibly small. But if they are the same size as regular tomato seeds they are not pure.

Both S. cheesmaniae and S. galapagense seem to be day length sensitive and only set fruit for (like some of the other wild tomatoes and hybrids) at the very end of the season in August-September. Some did not set fruit at all. A common myth of the Galapagos tomatoes is that they are hard to germinate with the reason being that they evolved to pass through the stomach of a tortoise before germinating. It is true that they are some-what hard to germinate, but they are not impossible to germinate without treatment with bleach or acetic or tartartic acid.

Germination is variable in this regard, and considering that not all islands where S. cheesmaniae and S. galapagense are found, don’t even have tortoises that visit them makes this supposition seem dubious at best. There could be some adaption to the islands in regards to germination, but i am inclined to believe at this point in time that it is an adaption to the soil with high volcanic ash (and thus high pH). After all, many if not most of the accessions of these from the TGRC directly mention that they were growing out of cracks in lava flows. A coincidence? I think not. Recommended seed treatment 50% bleach 50% water does indeed help germination a bit, but it is also recommended to prevent disease and seed borne pathogens. I suspect even soaking the seeds in plain water or soaking in lemon juice may also help germination, but i have yet to do an experiment that tests this idea.

It is obvious that the Galapagos continues to amaze us with it’s fantastic contributions to biological diversity, but what about some of the other wild tomato species? What secrets do they hold for the future of tomato breeding and future tomato varieties? It turns out a lot. Quite a lot actually.

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LA1777, Solanum habrochaites fruit, photo by Joseph Lofthouse.

Solanum habrochaites is the next species that researchers are paying attention to. It is from Ecuador and Peru in South America. It is hard to cross with domestic tomato lines, though not impossible, generally through one-way crosses by using the wild parent as the pollen donor and the domestic parent as the pollen recipient. It turns out lots of domesticated plants work this way, having lost the pickiness of their pollen receptors, while wild species are very picky about what pollen they accept.

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Solanum habrochaites, bold floral display. Photo by Joseph Lofthouse.

S. habrochaites has lots of genetic diversity within it’s species clade. One, like the most commonly requested accession, LA1777, is a unique off-type. Compared to the rest of the species of S. habrochaites, accession LA1777 has been classified as unique and having genes that may be desirable for introgression into commercial tomatoes.

LA1777 tends to grow small delicate and wispy. The stems on LA1777 are thin and only a couple feet long. The stems on other habrochaites accessions are thick, and grow 4 to 6 feet long. The stem on LA1777 is fibrous. The stems on other accessions snap when bent, like one might snap a young green bean. The leaves on LA1777 are smaller than other accessions.

LA1777 has an unobtrusive floral display that gets lost in the foliage. The floral displays on the other accessions were bold and carried high above the foliage. LA1777 is reported as having better tasting fruits, and not as much brown coloration in the fruits. And though it is reported as being Self incompatible (SI), it somewhat behaves as if it is Self Compatible, at least to some degree. S. habrochaites has both Self-Incompatible and Self-compatible forms.

It is sort of ironic then that LA1777 is the most requested accession of S. habrochaites from the TGRC even though it does not represent the species very well as a whole. However this may be explained by the fact LA1777 has become sort of standard accession in university research and published articles reflect that. But also from the research being done by big seed companies as well. One of the big seed companies tested LA1777 and found one unique gene that nearly doubles production of commercial tomatoes when it is introgressed into breeding lines. Between the university research and the seed companies, LA1777 has become the standard variety for most research on this species of tomato.

But caution should be noted as there may be much more diversity and worthwhile genetics in S. habrochaites than in just accession LA1777. I find it to be poor research that most of these published university studies have ONLY used ONE accession in comparison to domestic tomato varieties, namely accession LA1777. Shame on them.

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LA1777 on left, F1 hybrid on right. Solanum habrochaites outlier accession.
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Solanum habrochaites, photo by Joseph Lofthouse.
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Solanum habrochaites, photo by Joseph Lofthouse.

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S. peruvianum illustration, year 1828.

Solanum peruvianum is a well known and highly interesting wild tomato species. It’s name obviously hints at it’s origins being from northern Peru and Chile. Solanum peruvianum was originally thought to be a very diverse species of wild tomato, and it still may have much diversity, however it recently has been reclassified into four separate species: Solanum peruvianum, Solanum corneliomuelleri, Solanum huaylasense, and Solanum arcanum.

Solanum peruvianum has purplish fruit when ripe, along with green stripes similar to S. habrochaites. The fruits are said to be fruity and pleasant tasting when fully ripe, but not before. S. peruvianum is said to be harder to cross with commercial tomatoes. However, by using a bridge species that is more readily able to cross with domestic / commercial tomatoes it is said to be possible to move the S. peruvianum genome into the domestic tomato genome.

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S. peruvianum flowers, highly attractive to solitary bees in North America. Photo by Joseph Lofthouse.

S. peruvianum might have interesting genetics for it’s fruit characteristics and sugars. It also is said to contain some salt tolerance and ability to grow in harsh areas unhindered. It is also resistant to the tomato leaf curl virus. S. peruvianum is a mostly outcrossing species (Self-incompatible), with some Self-compatible accessions known and collected from isolated specimens. It seems to be fairly drought tolerant in my experience.

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One of two species of bumble bees that loved Solanum peruvianum flowers in my garden, Colorado, USA.

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S. chilense, flowering

Solanum chilense hails from the desert regions of southern Peru and Chile and hasn’t had much research attention paid to it, and thus i don’t have very much information about to share. However it has had some, and it has three main claims to fame. The first is that it is often cited as being a bridge species for S. peruvianum, and other distant species such as S. sitiens and S. lycopersicoides.

The second is that is said to be quite drought tolerant, having a unique root system unlike the other species that allows it to have a very deep root structure. In a desert environment having a deep root structure could be invaluable for surviving rough times.

The third is that this species supposedly has anthocyanin colored fruits and contains the “Aft” gene. The “A” gene being the gene that codes for anthocyanin production, and the “ft” referring to fruit. Haha, simple, but effective terminology.

The Aft gene has been introgressed from S. chilense into domestic tomato breeding lines and is directly responsible (in conjunction with other anthocyanin introgressed genes from S. cheesmaniae) for those new “Blue Tomatoes” you have been seeing on the market now. ‘Indigo Rose’ being the first official tomato variety of this kind. Indigo Rose, was developed from the Oregon State University tomato breeding program. The P20 blue tomato was a leaked breeding line from OSU that eventually became ‘Indigo Rose’. Indigo Rose was released after it was clear that many tomato breeders were already using P20 to breed better tasting blue tomatoes. ‘Indigo Rose’ does not have the best flavor as do most blue tomatoes at this time, but that is steadily being changed as more tomatoes are bred and crossed with each other for better flavor.

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The ‘Aft’ tomato (LA1996), growing in N. Colorado in 2017.

This last year, i had the opportunity to grow one of the precursor blue lines to ‘Indigo Rose’, LA1996, which is a determinate tomato, bears fairly large fruit, and has the Aft gene for anthocyanin fruit. LA1996 however does not have blue tomatoes, but rather a dirty blue speckled appearance. I kind of like it though, and i found it to be one of the few tomato varieties to do well in my garden, so i am keeping it. A great tomato variety for me. I have simply just been calling it ‘Aft’. Haha, not very original, but i don’t care.

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Solanum pennellii, a wild tomato species from Peru, with waxy leaves that help with drought tolerance.

The next species that holds great promise is Solanum pennellii from the dry regions of Peru. This species holds a wealth of potential genetics that domestic tomatoes could benefit from. The first is it’s small unique shaped leaves. These leaves also have a unique thick waxy coating on them that has been shown to help with conserving moisture and providing one form of drought tolerance. This is a completely different desert / drought tolerance adaption than S. chilense’s root structure, how exciting!

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Solanum pennellii flower close-up view. Notice how it has loose anthers and a unique curved and exerted stigma.

The excitement for S. pennellii does not end there however. Next notice the flower structure of this species. S. pennelli has both Self-Compatible (SC) and Self-incompatible (SI) forms, though the SI forms are more common. Like, S. habrochaites and many of the other wild species, This self-incompatibility or mandatory-outcrossing nature helps to ensure maximum genetic diversity within the species as possible.

The self-compatible species, including Solanum lycopersicum – the domestic tomato, Solanum pimpinellifolium, S. cheesmaniae, and S. galapagense, all have small uninteresting flowers with tight flower structures, non-exerted stigmas, and closed anther cones which make it hard for pollinating insects to visit them or make it worth their time.

This combination of large open flowers, exerted stigma, and unconnected anthers in S. pennellii make it very attractive to solitary bee species, including small Colletidae bees, Halictidae bees, and of course various species of bumble bees.

Solanum pennellii however has been praised in articles as being the most interesting species of wild tomato to work with because of unique acyl compounds. Basically the compounds that contribute to scent and flavor in fruit. Some Acyl sugars can be astringent and bitter, but some can contribute significantly to pleasant traits as well. Since S. pennellii differs from the common cultivated tomato quite significantly in this regard it is a highly interesting species to work with as it may lead to new tomato flavors and smells. I would regard S. pennellii to be the nicest smelling tomato species i have worked with yet because many of the F1 and F2 hybrids between [S. pennellii x domestic tomato] neither have the standard smell of domestic tomatoes, nor the sometimes stinky smell of some of the other species, instead on average S. pennellii hybrids smell quite like lemon-basil. A very nice smell for a tomato plant.

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F1 hybrid [domestic tomato x S. pennellii]. HUGE monster plant with wide branching growth. Highly attractive to native pollinating bees.
But that is not all! S. pennellii has reported salt tolerance just like the Galapagos species. But unlike the Galapagos species, it has all the above going for it and the fact that it’s hybrids grow HUGE! I mean HUGE monster plants. The combination of domestic genes with various desert tolerance in S. pennellii in hybrids make it a formidable plant and a great one to use as rootstock. In my climate here in Northern Colorado, where most varieties of commercial tomatoes fail to thrive in my soil and dry atmosphere, S. pennellii hybrids THRIVE! a testament to their will to survive. A badly needed trait in my own tomatoes here.

And finally, the last two wild tomato species i am going to mention are Solanum sitiens and Solanum lycopersicoides, two tomato species unique within the tomato clade. These two species, while probably having other traits in common with other wild tomatoes such as possible drought or salt tolerance, or disease tolerance, or blue fruits (S. lycopersicoides), their real uniqueness lies in the scented flowers they carry.

In all the groups of the domestic and wild tomatoes, none, other than these two species carry scented flowers. Perhaps a trait lost long ago and never really needed. Whatever the case may be, these two distant species carry scented flowers to attract various pollinating insects. S. sitiens flowers are described as stinky and volatile, with a “mothball-like” odor. Presumably this scent works best at attracting flies or beetles which may prefer the stinky smell. S. lycopersicoides on the other hand has flowers which are described as sweet and nectar-like, presumably to attract various bee or moth species that collect nectar. Studies between these two species and the distinct pollinators that visit them would be quite fascinating, especially when put into the subject of adaption, diversification, and evolution.

Breeding domestic tomatoes with wild tomatoes is a slow process. But it is interesting and the amount of segregating diversity is endless. Here are some photos of F1 tomato hybrids, F2, and various Back-crosses and segregates.

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Oh, and p.s. before i end this post, please note that i have started an experimental plant breeding wiki on my test website. I don’t claim it to be very good, but i am working on posting good pictures of wild tomatoes so that i can have a good reference to look back on to identify specific tomato species and the traits they have. Nobody other than myself will probably find such a wiki useful or interesting, but if for nothing else i want it for myself. There is currently extreme outdated or spotty, or missing info about these tomato species on wikipedia currently and the web is scattered with various information in little nooks and crannies. I wanted a central location that was easy to find. Hence, my tomato wiki.

Feel free to create an account and add your own photos or corrected information or cited sources to the wiki. The more people that help, the better it will be. The more photographs of various diverse species and accessions and angles and growers will also help a tremendous amount as well. Thank you.

https://biolumo.com/index.php?title=Tomato_Breeding_Database

Andrew’s Pea Breeding Tips [2017]

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As homage to my older blog post about pea breeding information, which is an archived copy of my currently defunct website, i wanted to share a few tips and a pea breeding technique that i invented that helps increase the rate of pea crossbreeding success and produces a higher seed per pod ratio than standard “paintbrush” or “scalpel” crossbreeding techniques.

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Standard Pea Crossbreeding technique is one that i call the “paintbrush method”. It works, i guess. But i think I’ve found a better way. In the paintbrush or scalpel crossbreeding method you basically find the two pea flowers you want to use. First you select a closed immature flower as the female parent that you then use with a small pair of scissors (lefthand curved embroidery scissors work well for this) to remove all the pollen anthers before they have a chance to release mature pollen and self pollinate. Second, you then take an open mature pea flower to use as the male flower and use a paintbrush or scalpel to collect pollen and transfer it to the receptive style/stigma.

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Andrew’s Pea Crossing Method:

My method is a bit odd looking at first, but in my experience it works MUCH better. On average from what i can tell you usually get about 1-2 peas per pod with the “paintbrush method”. No more than 4. With my method i’d say you get on average of¬†4-5 peas per pod, with the potential of a whole pod 6-8 peas depending on your variety. So i’d say I’ve at least doubled the success rate, maybe even tripled it.

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First, i’d say get rid of that embroidery scissor. While it works, i find that a combination of pulling off the outer petals with your hands and using a small flat beveled or angled pair of tweezers works fantastically well. Get yourself a pair of tweezers like these. They may be referred to as “eyebrow tweezers”.

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Second, find yourself an immature pea flower to use as the female parent. Rip off all the outer petals and remove the immature anthers before it can self-pollinate. Third, find yourself an open mature flower for the male parent. Just cut or rip the whole flower off of the plant, we will need the whole thing. Fourth, use your tweezers to make a small opening in the bottom of the keel petal. Followed by slipping the flower used as the male over the stigma and style of the flower used as the female parent, making sure that the stigma/style gets covered in pollen at the top of the keel petal shown in the picture above. There is a small reservoir of pollen up there that makes for plenty of pollen to go around. Finally, leave this flower covering on there as long as possible. Sometimes they fall off, it helps to try pollinating the flower again during the next few days if this happens.

Why is this technique more successful?

Well, for me i think it’s a combination of things. First and most importantly it serves as a hood or covering for the flower to keep pollen from drying out or being washed away in the rain. In my climate the air can be quite dry and the high altitude with intense sunlight tends to wick away moisture quite easily. These tiny pea styles are quite delicate and seem to dry out so quickly that they can dry out before pollen has been able to set seed. Second, it provides a LOT of pollen over that whole style. I could be wrong, but i suspect that each of the receptive seed ovules mature at different times. If this is true, then it requires enough good pollen to be available over several days for each seed to be pollinated and grow. And finally, it just seems to mimic everything about how a pea flower would naturally self pollinate. Sometimes it’s best to just imitate nature as sometimes nature knows best.

How do you know what age of pea flower to use?

Good question. Here is a good illustration that should help. You need to catch a pea flower used as the female parent very very early actually. The pea flower second from the left is just about perfect because it is big enough to use but young enough it should not have released pollen and selfed yet. The open flower on the far right is about right for using as a pollen donor. If the pollen is too old or not enough, select a similar one that is slightly younger or try one that looks like the third one from the left.

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And that’s it. If you have any thoughts, please leave a comment. I hope you find it interesting and helpful. Happy Tinkering! ūüôā

http://daughterofthesoil.blogspot.com/2007/05/how-to-breed-your-own-garden-peas.html

8. Pea Breeding by Earl T. Gritton

http://daughterofthesoil.blogspot.com/2006/06/how-to-hybridise-garden-peas.html

New Watermelon Breeding Project 2018 and Beyond…

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Today i’m sharing about a new plant breeding project i am planning on working on. The Watermelon Landrace project I’ve been developing for Northern Colorado has started to progress quite well and i am very pleased in the direction it is heading. This past summer of 2017 i harvested many that were of decent size, grew in my soil, and tasted excellent. I started to eliminate the ones that still develop blossom end rot and other poor traits such as funky shape or poor flavor. Starting to only save the best seeds.

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I originally added some Colorado Red-seeded Citron melons to my watermelon landrace because i wanted to breed watermelons with red seeds and frost tolerance. Citron Melons are supposed to be pretty damn hardy and supposedly have this desired frost tolerance. The problem? Citron melons aren’t exactly edible. They are not poisonous, just super hard white flesh and bland bland bland. Actually they are a very old heirloom type of watermelon called the Colorado Preserving Melon or the Colorado Red-seeded Citron. Apparently they have lots of natural pectin in them which is useful for making jams and jellies for toast. And did i mention they can breed quite easily with modern watermelons?

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When it comes to the Colorado Red-seeded citron i absolutely love their red seeds. I really want that trait in my watermelon landrace. I guess there are a few red seeded watermelon varieties out there already, but they are few and far between.

So, what happens when you breed a modern red or yellow fleshed watermelon with a citron melon? Well, i don’t exactly know. Yet. This year i planted a few of the red seeds i harvested from the citrons from last year that were mixed in with the landrace. The seeds i got were all still red so i figured they probably self pollinated. Regardless i added them to the landrace watermelon seed i planted this year in hopes that they would grow (not die), cross, and produce viable seed.

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I’m happy to report that so far that part of the project was a success. The top photo above shows what i think are confirmed F1 Citron x Watermelon hybrids. I suppose they could be F2, but i’m just going to assume F1. The seed was harvested from fruits that showed the characteristic “white cloverleaf striped mottling” that Citron Melons have, and from fruits that had hard white bland flesh when all the other watermelons had ripe yellow or red flesh. How do i know these seeds are hybrids? Well because the seeds were not red this time! In fact they were all different kinds of patterns and colors. Some red-black, some pure black, some greyish, some grey-black-mottled, etc.

Looking forward to growing this line of seeds out and reselecting for the traits i want. Red seeds would be awesome, but not necessary. Frost tolerance would be even more awesome, but not necessary. Even without those traits what impresses me most about Colorado Citron Melons is the fact that they grow so darn well in my climate, with my poor soil, and still grow full size melons even when over crowded with other watermelons that don’t do well, and even thrive with relatively low amounts of water. These traits alone are so very desirable to be folded into my watermelon landrace that this project is so exciting even now when i’m just beginning.

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I’ve heard a rumor that way back the Soviet Union (USSR) did lots of plant breeding experiments (maybe because of the breeding genius known as¬†Ivan Vladimirovich Michurin), and part of these experiments involved Wide Hybridization or Distant Hybridization, which means crazy breeding like interspecific, intergeneric, intrageneric, and intraspecific breeding and attempted crosses that most people would never try or attempt. Some of these crosses were successful. What i’m interested in is the Soviets work on Citron-Watermelon hybrids. Apparently they experimented with these long before i have and rumor has it that they were able to recover some nice tasting watermelons that were able to be stored for several months into the winter. Awesome. I will update this blog post when i have more information about this. There are already supposed “Winter Watermelons” that supposedly keep for several months, but i’m sure those can be improved, or i can just breed my own winter watermelon variety. Exciting stuff!

Edit Nov-15-2017:

Okay, so i finally received¬†a copy of the rare book titled “Wide hybridization of plants (Otdalennaya gibridizatsiya rastenii) Proceedings¬†of¬†the Conference on¬†Wide Hybridization of Plants¬†and Animals; collection¬†of¬†reports” from inter-library¬†loan. A mouthful, i know. Thanks to WorldCat to helping me track it down. Not many copies of it left around.

Originally¬†written and published in Russian in the U.S.S.R. in 1958, and Translated into English in Jerusalem Israel in 1962.¬†The Soviet Union was known in those times for great scientific advances including launching the space race, the first cosmonaut in space, Sputnik, and other crazy medical advances like the Skenar and Bacteriophage medicine, to strange sci-fi spy weapons in the Cold War. Apparently they also were advancing in novel plant breeding techniques¬†and programs. Michurin was one of these guy’s. If you’ve never heard of him or his plant breeding techniques¬†and success go look him up. I honestly don’t know much about him myself, but i do know he was an accomplished plant breeder, most notably with wide genetic crosses that noone else thought would work.

Anyway, back to the Interspecific Hybridization of Watermelon work done by the Russians with Citron x Watermelon crosses in 1958. Turns out they did have success with it. The F1 generation¬†was mostly like the wild Citron with bland hard tasteless flesh. F1 and F2 Hybrids with¬†Citrullus colocynthoides are similar to their wild Citron parent genetics. Late-ripening, coarse compact unsweet fruit pulp and a thick rind. Quite unremarkable. But that’s what i was already expecting. One cool note though is that some of these in future segregating generations or backcrosses to domestic watermelons can produce some sweet watermelons that have some storage ability. Meaning they ship well and can store for many months. In fact some of them get sweeter over time whereas¬†domestic watermelons do not. So all in all some cool potential in the project after all! I’m even more excited now!

If you want to read the Soviet’s 1958 watermelon research yourself, i have taken the effort to scan some of the book into a PDF for you. It’s not the whole book, but it has the relevant chapter on Watermelon and Citron crosses.

Here’s the PDF:¬†Wide_hybridization_in_plants_TSITSIN

In [2017] I bred A New Pea Variety With Purple Seeds!

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these are new F2 seeds recovered from some pea crosses i did i think in spring/summer of 2015. So two years ago. This one is the descendant of a cross done between a rare, and nearly extinct variety of pea that has a dominant gene for having a purple testa color over the seed coat. The parent variety called ‘Purple Passion’ has small round dark purple seeds and grows on thin wispy and pathetically weak vines. Hardly seems domesticated at all. The other parent of the cross was a “super dwarf”, or Extra Dwarf as some literature calls it, of a short (1-2″ tall) but robust pea with thick stems, big leaves, large seeds, and a charming personality. For a plant that is. Not that plants have personalities, but whatever. The result in the F2 generation is this. A large good sized seed with the characteristic dark purple testa seed coat color. Pretty awesome. I’m excited to furthur grow this line out and see what it becomes. This is different from the Brick-red seeded peas known as ‘Biskopens’ or ‘Sweedish Red’, which are a brick-red color rather than dark purple / violet and which is a recessive trait rather than a dominant one. Biskopens is a neat variety in it’s own right, and i have recovered some interesting F2 recombinant offspring from some crosses of that variety as well.

Not sure what i should name it yet. Depends on what it turns into really. Assuming i was able to recover the “super dwarf” genetics at some point i might name that substrain something like ‘Purple Midget’ or something like that. haha

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Parent Variety: ‘Purple Passion’
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F1 seeds of cross between ‘Purple Passion’ Pea and ‘Mighty Midget’ Pea

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Growing Watermelon Landrace in Colorado 2017 Success!!!

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Most of the watermelons are done for the year and eaten already. Many of them were good tasty Canary Yellows. One Salmon-yellow and one Pink were so/so. I’m trying to not save seeds from now on from any that taste bland like the salmon-yellows. Or others that grow poorly. I think i will also start selecting against those that have bacterial rot at the flower end and those that split open. But i’m happy in the direction these are headed. I have a side breeding project where i am letting some Colorado red-seeded citron being pollinated by the landrace watermelon. I’m hoping that in the future that leads to a more cold-tolerant yellow fleshed red-seeded watermelon strain. Some seeds from those are all crazy colors this year with some partially red-black and others with unique gray spots. Just a side project for now.

Generally the small bowl-sized watermelons are from my garden. I had the opportunity to have a small local organic farmer grow some of the landrace watermelons for me in fertilized soil and on black plastic. Those ones grew a little bigger for him. I was able to purchase and collect a few of those back. The long one looked like a yellow-fleshed Lofthouse Charleston Gray strain to me… but i don’t know for sure. I cut it open a little early. Apparently the long ones take longer to ripen so the dry three-tendril method didn’t exactly work on those, but it did for my small round ones!

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All in All i’m happy to finally be able to grow decent sized tasty watermelons here in the heart of Northern Colorado. Where few are able to succeed at growing watermelon at all! Success!!!!

Improving the Tomato Genome by breeding with wild tomatoes [2017]

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Solanum peruvianum (wild tomato with desert tolerance)

So i haven’t written a blog post in some time. Sorry about that. It has been very hectic this year. That’s not to say that i’m completely dead. And despite my busyness and absence i am still dabbling a little bit in the garden and plant breeding scene. I didn’t have the time, energy, or space to work on my purple Indian Corn or Teosinte this year. I barely made room for beans, peas, tomatoes, and a row of watermelon.

The beans are my special four corners native beans which include, New Mexico Red Appaloosa (aka. Gila River bean), Anasazi, Zuni Gold, Rio Zape, and maybe a few others. The Peas are a large growout of my 17-23 different varieties of genetically unique and rare pea varieties, some of which are segregating crosses that i did two seasons ago. And tough i don’t have many pictures i will post one below of a purple podded umbellatum-type (aka. crown pea) where all the pods come out in a jumble all at once. To have a purple podded one of these is new and kind of cool. I hope to have a yellow and red-podded umbellatum-type pea someday. The watermelon are the result of mine and Joseph Lofthouse’s Watermelon Landrace project. Joseph Lofthouse seems to be world famous now for his widely successful landrace seed varieties and breeding techniques.

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Purple Podded Umbellatum Crown Pea

Anyway, back to the tomatoes. The Tomatoes are a brand new project and sort of an offshoot of one of Joseph’s new landrace breeding projects as well and a few other fellow collaborators and breeders as well. It all started when Joseph was working on wanting to convert tomatoes to a landrace like many of his other successful crops. But there are a number of problems with that and domestic tomatoes in general.

The first problem is that domestic tomatoes are entirely self pollinating and don’t outcross all that much and have tiny closed-up flowers. Another problem is that domestic tomato flowers are not very attractive to pollinators. And the third major problem is that domestic tomatoes went through several genetic bottleneck selection events when they were domesticated that they have a very narrow genetic base. This narrow genetic base means that 1. Most tomatoes are subject to easily succumbing to disease and 2. that when they do outcross there is not much variation anyway. An average bad-tasting disease susceptible red tomato that crosses with another¬†average bad-tasting disease susceptible red tomato means that in the end all you really get is more of the same.

My interest in all of this starts with the basic fact that in my climate here in Northern Colorado with my soil (mostly a dry clayish sandy soil where mostly desert plants grow), and the high altitude with intense sunlight and UV and the dry wind that wicks moisture out of the ground means that most garden varieties of anything don’t do all that well here unless intensely babied. This applies most especially to tomatoes. Even worse when it comes to Heirloom tomatoes. Sure heirloom tomatoes generally taste better, but to have a tomatoe plant produce like ONE good tomato through a whole season… That’s a MAJOR FAILURE in my book.

There are lots of tomato freaks out there that try to tell me that here in Colorado i can grow ANY tomato variety and be successful. And while that might be true if i replaces all my soil with compost or potting mix and provided massive amounts of water, and started them all early and planted them all out perfectly then yes maybe that would be true. But that’s not what i want to do, not should i have to do that. I should be able to just start a tomato plant and plant it where i want and not have to worry about it all that much and have it produce a decent harvest (whatever that happens to be). And not have to worry about disease, or growing slow, or not being adapted to my soil or the intense UV light or whatever. That’s where all this plant breeding comes in.

The goal(s): 

  • To breed a superior tomato variety that does well for me (in dry N. Colorado)
  • To increase the genetic diversity in the tomato genome by using wild tomatoes
  • To create or recreate a tomato that is highly attractive to pollinators
  • To create a population of tomatoes that are highly outcrossing
  • To create a tomato that i actually think tastes good and NOT like cardboard

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wild tomato seeds. photo courtesy of Joseph Lofthouse

This project is still in it’s early stage, but it is progressing nicely. On Joseph’s end he is having huge success by using wild tomatoes bred with domestic tomatoes that have large showy flowers with exerted stigmas and have lots of pollen available that make them attractive to bumblebees. He is using mostly Solanum habrochaites but is starting to branch out to other wild tomatoes as well. Others are working on breeding tomatoes that produce a good harvest in under 100 days from being direct seeded and that have frost tolerance.

On my end i am experimenting with as many wild tomatoes that i can. I am evaluating several accessions of wild Galapagos tomatoes which so far are not doing much. The S. habrochaites also are not doing much. The ones i am having excitement from are the Solanum peruvianum which have silvery leaves and desert tolerance (in the roots) and a F1 hybrid between a domestic tomato and Solanum pennellii which has a different form of desert tolerance (in the leaves). I am excited about these genetics since they seem to be growing very well in my garden. The largest of any of my tomatoes is this F1 hybrid of S. pennellii. It is HUGE!!

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F1 hybrid between domestic tomato and Solanum pennellii
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Flowers of an F1 hybrid between domestic tomato and Solanum pennellii
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F2 cross of domestic tomato and Solanum habrochaites