Plants for all

Prelude:

While I was moving some tomato plants around earlier this week, I couldn’t help but notice that they felt a little… prickly. Ouch! Close examination of tomato plants reveals that they are covered in tiny hair-like structures, which give them this texture (Figure 1). The next time you see a plant, you might also notice that many of them are sort of… fuzzy. Why? Because they’re covered in trichomes! Trichomes are projections of the epidermis – made of living cells – which perform a variety of important functions, including protecting plants against predators, limiting water loss, and shielding plants from solar radiation [6].

Since trichomes are easy to see under the microscope (and make pretty pictures!), I figured that now was as good a time as any to talk a little bit about them.

Figure 1. Large, hair-like trichomes on the stem of a beefsteak tomato plant. Left: Phone camera image; Right: Microscope image at 50X magnification.

Trichomes in tomato:

Now, I’ve spent a lot of time looking at Arabidopsis trichomes under the microscope. Why? Because they’re large single cells, transparent, and have particularly ginormous nuclei, possibly as a result of endoreplication – where DNA is repeatedly copied, but a cell doesn’t divide [5]. All of these traits are great if you want to image nuclei.

Imagine my shock when I looked at tomato trichomes under the microscope. They’re multicellular – and there is more than one type! Looking back, I really shouldn’t have been surprised at all. Many species of plants have multicellular trichomes, including sunflowers – We’ll talk about those in a minute.

You’re already acquainted with the long, hair-like trichomes in tomato (See Figure 1). What other kinds are there? To have a look, I scraped some epidermal cells off my Indigo Blue Beauty tomato plant and stuck them under the microscope. If you remember my first blog post about anthocyanins, I lamented at the difficulty of getting clear images of epidermal cells under the microscope. All of my images look like Figure 2 left (see below).

Figure 2. Tomato epidermis at 100X magnification. Left and right panels show exactly the same sample; I just changed the focus on the microscope! The tips of glandular trichomes can be seen in the image on the right. 

Blech! Why so blurry? The answer is glandular trichomes… they stick upwards out of the epidermis, and out of the plane of focus… which makes everything behind them blurry. By adjusting the focus on our microscope, we can see the ends of the of these trichomes clearly (Figure 2 right). The trichome tips are made of clusters of 4 cells, which sit at the end of a narrow stalk.

I particularly like the image I captured in Figure 3, which shows 3 types of tomato trichomes sitting next to each other. The large hair-like trichome is HUGE and goes way off the end of the picture, while the small hair-like trichome and glandular trichome are tiny by comparison. Despite their enormous size, the large hair-like trichomes are still only one cell thick – and you can see them with the naked eye! Pretty neat. For your reference, the different types of tomato trichomes are nicely summarized by Tissier (2012) [12].

Figure 3. Tomato epidermis imaged at 100X magnification and blown up even further to show detail. From left to right: A large hair-like trichome, a small hair-like trichome, and a glandular trichome can all be seen side-by-side.

Great! So what do all these trichomes actually… do? The predominant idea is that tomato trichomes are primarily for defense against predators such as insects [12], though they may also play a role in water use efficiency and drought tolerance [4]. The hair-like, non-glandular trichomes (NGT’s) form a mechanical barrier to keep insects away from the surface of the plant, and may also damage the digestive systems of insects [11]. I couldn’t find a ton of information about NGT’s in tomatoes specifically, but I did come across this study in a related species, Solanum carolinense, which found that NGT’s impair feeding and weight gain in tobacco hornworm caterpillars [11].

How about the glandular trichomes? I came across this interesting paper which demonstrates that fluid in the glandular trichomes is released as they come into contact with insect foes; The fluid sticks to insects and makes it difficult for them to move [10]. They even have video of this happening in their supplementary data [10]! I highly recommend. Anyway… The glandular trichomes also contain chemicals which inhibit insect feeding. For example, secretions from glandular trichomes are known to elicit stress and starvation responses in aphids [9]. The glandular trichomes in the wild tomato relative Solanum habrochaites produce a compound called zingiberene, which inhibits feeding by aphids [3]. One interesting study crossed this species with domesticated tomato to determine if it would be possible to breed tomatoes with increased aphid resistance [3]. The importance of this research to society is clear; if we want to continue to eat tomatoes en masse, we need to know how to protect them!

Before we move on, I’d just like to muddy the waters a bit with this thought: Tomatoes use trichomes to repel insects that want to eat them. This has an unintended consequence: Predators which eat the insects which eat the tomato may also be repelled by the trichomes!

In the wild, this is less of an issue; The tomato is on its own and needs to protect itself by any means necessary. But when tomatoes are grown domestically, humans give them help in the form of biological pest control – introducing predators to eat the pests. Trichomes may actually make this form of pest control less effective [7]. Therefore, using tomato varieties with lower trichome densities might paradoxically make it easier to control pest populations [7]. However, more work is needed to determine the efficacy of this approach.

Trichomes in sunflower:

Like tomatoes, sunflowers also possess multicellular trichomes of several different varieties. They have large, hair-like trichomes which give mechanical protection (easily visible on the developing head of a Teddy Bear sunflower, see Figure 4 left). They also have much smaller linear glandular trichomes (LGTs) – multicellular structures that resemble tiny strings of pearls (Figure 4 right bottom). As LGTs develop, the nuclei in the cells at the end of the trichome disappear, and these cells start to accumulate terpene compounds [2]. Terpenes are known to have insect repellent properties, implying that LGTs probably play an important role in insect defense [2].

Figure 4. Left: The developing head of a Teddy Bear sunflower is covered in white hairy trichomes. Right top: Sunflower bract at 100X magnification, showing both hairy trichomes and smaller linear glandular trichomes. Right bottom: Close-up of a linear glandular trichome at 400X magnification.

For fun, I also had a look at some trichomes from the stem of my chocolate cherry sunflower (Figure 5). One thing you might notice right away is that the epidermal cells surrounding the hair-like trichomes lack the purple pigmentation found in the rest of the epidermis. I have no clue why this is, but it is interesting! The other observation I made is that the LGT’s often emerge from heavily pigmented areas of the epidermis, but contain no purple pigment themselves. Again, I have no idea why, but it is interesting.

Figure 5. Left: The stem of a chocolate cherry sunflower. Right top: Stem epidermal cells at 100X magnification, showing hair-like NGT’s and comparatively tiny LGT’s. Right bottom: A zoomed-in picture of an LGT protruding out of a heavily-pigmented patch of epidermal cells.

Trichome guests of honor:

This part is just for fun! I have a microscope… and I have a bunch of different plants to look at… so why not just check to see what I can see?

I started with an eggplant plant. It doesn’t have visible hairs; instead, it is covered in a fine white fuzz. Closer examination reveals the presence of stellate (star-shaped) trichomes (Figure 6). They’re pretty crazy looking!

Figure 6. Trichomes from the stem epidermis of an eggplant.

I also had a look at a random plant growing near the house. I don’t know what it is exactly, other than the fact that it is a member of the mint family. It is absolutely covered in tiny hairs, giving it a silvery appearance (Figure 7 left). I just had to look at those under the microscope (Figure 7 right). Wow, so many!

Figure 7. Trichomes on a “mystery mint”. Left: A whole leaf, showing its fuzzy appearance. Right: Epidermis under the microscope.  

Gene of the week!

I am sorry for not talking more about the genetics underpinning trichome development. This lackluster performance is simply because I procrastinated and am running out of time I felt that a small blog post introducing the concept of trichomes wouldn’t do the topic justice.

Despite this, I am pleased to present our Gene of the Week! I couldn’t find an account of a tomato or sunflower mutant completely lacking trichomes… darn. However, the GLABRA1 (GL1) gene in Arabidopsis is required for trichome formation! The gene’s name comes from the word “glabrous,” which means “hairless.” Loss-of-function gl1 mutants in Arabidopsis lack trichomes [8]. The GL1 protein is a transcription factor, meaning that it interacts directly with DNA and affects the expression of other genes [8]. In this case, these other genes just happen to be required for differentiation of epidermal cells into trichomes. According to the UniProt databse, the GL1 gene is located at the AT3G27920 locus on Arabidopsis chromosome 3, and codes for a protein which is 228 amino acids long, with a mass of roughly 26 kDa.

Figure 8. Alphafold structure of AtGL1, taken from: https://alphafold.ebi.ac.uk/entry/P27900. The 2-part DNA-binding domain can be seen in blue (which indicates a high degree of confidence in the predicted structure).

I did a quick search of the OMA database (https://omabrowser.org/oma/home/) to see if there are any known orthologs of GLABRA1 in tomatoes/sunflowers [1]. Orthologs are genes from different species which share a common ancestor. Identifying an ortholog of a gene with a known function in Arabidopsis in another plant species can allow us to guess that gene’s function (though of course only experiments can give us definitive information!). Surprisingly, the OMA database does not show any orthologs of GLABRA1 except in other members of the Brassicaceae family, of which Arabidopsis is a member. This raises the intriguing possibility that the transcriptional machinery which controls trichome development in the Brassicaceae may be different from those in other plant families.

Works cited:

[1] Altenhoff, A.M., Vesztrocy, A.W., Bernard, C., Train, C., Nicheperovich, A., Baños, S.P., Julca, I., Moi, D., Nevers, Y., Majidian, S., Dessimoz, C., & Glover, N.M. (2024). OMA orthology in 2024: improved prokaryote coverage, ancestral and extant GO enrichment, a revamped synteny viewer and more in the OMA Ecosystem. Nucleic Acids Research 52(D1), D513-D521. DOI: 10.1093/nar/gkad1020

[2] Aschenbrenner, A., Horakh, S., & Spring, O. (2013). Linear glandular trichomes of Helianthus (Asteraceae): morphology, localization, metabolite activity and occurrence. AoB Plants 5, plt028. DOI: 10.1093/aobpla/plt028

[3] de Oliveira, J.R.F., de Resende, J.T.V., Maluf, W.R., Lucini, T., de Lima Filho, R.B., de Lima, I.P., & Nardi, C. (2018). Trichomes and Allelochemicals in Tomato Genotypes Have Antagonistic Effects Upon Behavior and Biology of Tetranychus urticae. Frontiers in Plant Science 9. DOI: 10.3389/fpls.2018.01132

[4] Galdon-Armero, J., Fullana-Pericas, M., Mulet, P.A., Conesa, M.A., Martin, C., & Galmes, J. (2018). The ratio of trichomes to stomata is associated with water use efficiency in Solanum lycopersicum (tomato). The Plant Journal 96(3), 607-619. DOI: 10.1111/tpj.14055

[5] Kasili, R., Huang, C., Walker, J.D., Simmons, L.A., Zhou, J., Faulk, C., Hülskamp, M., & Larkin, J.C. (2011). BRANCHLESS TRICHOMES links cell shape and cell cycle control in Arabidopsis trichomes. Development 138(11), 2379-2388. DOI: 10.1242/dev.058982

[6] Kaur, J., Kariyat, R. (2020). Role of Trichomes in Plant Stress Biology. In: Núñex-Farfán, J., Valverde, P. (eds) Evolutionary Ecology of Plant-Herbivore Interaction. Springer, Cham. DOI: 10.1007/978-3-030-46012-9_2

[7] Lou, T., Maria, N., Marie-Stéphane, T., & Navia, D. (2024). Tomato trichomes: trade-off between plant defenses against pests and benefits for biological control agents. Open Science in Acarology 64(4), 1232-1253. DOI: 10.24349/ej2w-b311

[8] Oppenheimer, D.G., Herman, P.L., Sivakumaran, S., Esch, J., & Marks, M.D. (1991). A myb gene required for leaf trichome differentiation in Arabidopsis is expressed in stipules. Cell 67(3), 483-493. DOI: 10.1016/0092-8674(91)90523-2

[9] Planelló, R., Llorente, L., Herrero, Ó., Novo, M., Blanco-Sánchez, L., Díaz-Pendón, J.A., Fernández-Muñoz, R., Ferrero, V., & de la Peña, E. (2022). Transcriptome analysis of aphis exposed to glandular trichomes in tomato reveals stress and starvation responses. Scientific Reports 12, 20154. DOI: 10.1038/s41598-022-24490-1

[10] Popowski, J., Warma, L., Cifuentes, A.A., Bleeker, P., & Jalaal, M. (2025). Glandular trichome rupture in tomato plants is an ultra-fast and sensitive defense mechanism against insects. Journal of Experimental Botany, eraf257. DOI: 10.1093/jxb/eraf257

[11] Kariyat, R.R., Smith, J.D., Stephenson, A.G., De Moraes, C.M., & Mescher, M.C. (2017). Non-glandular trichomes of Solanum carolinense deter feeding by Manduca sexta caterpillars and cause damage to the gut peritrophic matric. Proceedings of the Royal Society B 284(1849), 20162323. DOI: 10.1098/rspb.2016.2323

[12] Tissier, A. Trichome Specific Expression: Promoters and Their Applications. Editor: Yelda Özden Çiftçi. Transgenic Plants – Advances and Limitations. Publisher; 2012:353-378. Accessed August 8, 2025. DOI: 10.5772/32101

Supertall

This week I’d like to draw your attention to these two sunflower varieties I have growing on my deck (Figure 1). Bear in mind that all of these plants belong to the same species of sunflower, Helianthus annuus. The pot on the left contains two individuals of the cultivar “Lemon Queen,” while the pot on the right contains three individuals of the cultivar “Teddy Bear.” Seeds of each variety are easily acquired if you want to try growing them yourself.

These plants are the same age and have been growing in the same conditions in the same type of soil. Lemon Queen is a typical height for a sunflower plant. So why the heck is Teddy Bear so short?? The short answer (hardy har) is that I don’t know precisely why. But the journey that led me to this earth-shattering conclusion was intriguing nonetheless! Join me as we go down a veritable rabbit hole about sunflower plant height.

Figure 1. Sunflower “Lemon Queen” (pot on the left) vs. “Teddy Bear” (pot on the right).

Why are dwarf sunflowers desirable?

There are many varieties of dwarf sunflower available to buy, and they are desirable for a few reasons. Their compact size means that they can be grown when space is limited, and smaller flower heads fit nicely into cut flower arrangements.

You might wonder whether smaller sunflower varieties mature faster, since they do not need to grow as much before flowering. This is not necessarily the case; My Teddy Bear and Lemon Queen plants flowered at roughly the same age. However, we can address this question more broadly by using the data stored in the HeliantHome database [4]. They have plant height and flowering time data for hundreds of individual plants representing roughly 60 distinct wild populations of Helianthus annuus. Is there a correlation between plant height and flowering? If we plot plant height against flowering time, we can clearly see that there is a strong correlation (Figure 2). From this, we can say that amongst wild populations, sunflower plants that flower earlier tend to be shorter.

There is a caveat, however. It is not clear whether the short plants in this dataset are true dwarf varieties, or whether they are simply short because they were grown in conditions which are not ideal for them. Stress may also affect plant growth and flowering time.  

Figure 2. Days to flowering vs. plant height at flowering (cm). Data are taken from the HeliantHome database [4].

Zooooooom!

Sunflowers, like all plants, are made of cells. Therefore, the dramatically short stature of the Teddy Bear sunflower could be due a to 2 factors:

1. It could have shorter cells in the stalk, OR…
2. It could have less cells overall in the stalk, OR… both!

To see what’s going on here, I peeled some epidermal cells off the stalks of my Lemon Queen and Teddy Bear plants and estimated their height under the microscope. I sampled both Lemon Queen plants and all three Teddy Bear plants.

How do we estimate cell height? We use a calibration slide, of course! It’s essentially a tiny ruler printed on a microscope slide that acts as a point of reference for what we’re seeing. It looks like this:

Figure 3. Markings on a calibration slide at 100x magnification. The distance between the smallest lines is 0.01 mm (or 10 µm).

Problem: How do we pick which cells to measure, and how do we measure them? This is admittedly arbitrary. My estimate of average cell height is just that… an estimate. I took the cell samples halfway up the stem of each plant, so the cells were hopefully about the same age. I picked a sample of 10 cells close to my ruler with clearly-defined borders, and I measured their vertical height (See Figure 4, samples are lying horizontally). Length measurements were done using a free image analysis program called FIJI.

Figure 4. Microscopy images of the cells used to estimate cell size in Lemon Queen (Left) and Teddy Bear (Right). Colored bars indicate where length measurements took place.

Table 1: Epidermal cell heights (in µm) in two different sunflower cultivars.

While there might be a slight difference, I wouldn’t say that Teddy Bear has dramatically smaller cells than Lemon Queen. In fact, the arbitrary nature of my sampling method does not give me fabulous confidence that this difference is meaningful at all. Based on this, I would say that the reduced height of Teddy Bear plants is almost entirely due to a smaller number of cells.

Just for fun: My Lemon Queen plants clocked in at an average height of 81.25 inches (2,063,750 µm), and my Teddy Bear plants had an average height of 19.33 inches (490,982 µm). Using our average values for cell height (see Table 1), we find that our average Lemon Queen plant is ~29,000 epidermal cells tall, while the average Teddy Bear plant is just ~8,000 epidermal cells tall.

What genetics cause dwarfism in sunflowers?

Surprisingly, I could only find one study which definitively identifies a genetic cause for dwarfism in sunflowers. Fambrini et al. determined that a loss-of-function mutation in a gene called HaKAO1 results in sunflower plants with an extreme dwarf phenotype [3]. HaKAO1 codes for an enzyme which helps to produce hormones called gibberellins; Without it, plants produce less gibberellins, and do not grow as large [3]. However, the phenotype of their mutant line (called “dw2”) was much more extreme than the dwarfism we see in Teddy Bear plants. Furthermore, a defining feature of the dw2 mutant is small cell size, which Teddy Bear lacks (see above). Therefore, a mutation in HaKAO1 is unlikely to be responsible for the short stature of Teddy Bear sunflowers.

Without a direct source to tell me why Teddy Bear sunflowers are short, I had to resort to more desperate measures. One idea I had was to look for genome-wide association studies (GWAS) which include Teddy Bear in their sampling population. What is GWAS? Basically, we look at variable genetic elements in a large group of individuals, then we look at a phenotype (for example, height) in these individuals, and finally we look for statistically significant associations between particular genetic variants and the phenotype. Doing this allows us to pinpoint specific genetic loci which might affect our phenotype of interest, which we can then test in further experiments.   

One common kind of variable genetic element used for GWAS is the SNP (single nucleotide polymorphism). SNPs occur when a single DNA base pair is exchanged for another one. For example, in a hypothetical DNA sequence ATGCATC (only one strand shown), replacing the middle “C” with a “G” (like this: ATGGATC) constitutes a SNP. SNPs are handy because they are easy to detect, and because they are very common in many genomes, giving good coverage.

So anyway, my first idea was… look for GWAS studies which examine sunflower height… then check if Teddy Bear was used in their sampling population… then check whether Teddy Bear has any SNPs which strongly correlate with height! I could only find two sources of GWAS data which examined sunflower plant height. The first source was a dataset published by Delen et al. (2024) [2], and the second source was a dataset published by Todesco et al. (2020) and linked through to HeliantHome [7]. But neither dataset had Teddy Bear in their sampling population! Nuts.

Figure 5: These plots are taken directly from the EasyGWAS page, which represents the Todesco GWAS dataset [7]. Top: Manhattan plot showing position of SNPs on sunflower chromosome 7 (x-axis) and statistical association of these SNPs with plant height (y-axis). One SNP with a statistically significant association with height is highlighted by the red arrow. Bottom: Distributions of plant height for plants with different variations at the SNP locus identified in the Manhattan plot above. Plants with the G/G allelic combination tend to be shorter than those with T/T or G/T.

OK, what now? Well, the Delen and Todesco datasets give us a set of SNPs which have a strong correlation with plant height. A genome assembly for Teddy Bear is not available. But there might be SNP data for Teddy Bear in another GWAS dataset! In theory, I might be able to use such a dataset to check whether Teddy Bear has any SNPs which are associated with plant height.

Alas, I only found a single GWAS source which contains Teddy Bear; Talukder et al. (2019) [6]. Then I encountered another problem… the genetic maps that Talukder, Delen, and Todesco used to denote the location of their SNPs are different [2][6][7]! And reconciling different genetic maps is no trivial task, especially if full sequencing data isn’t available. Without more data, my dreams of identifying a possible genetic reason for the Teddy Bear’s short stature have been dashed. I guess we can’t always get what we want. (But seriously, if you have any ideas, help would be greatly appreciated!)

Gene of the week:

After that rather uninspiring conclusion, let’s now have a little pick-me-up with Gene of the Week ™ ! (EDIT: I’ve been informed that I need to clarify that the trademark is merely a joke, for legal reasons). Since it’s the only gene we really discussed in this post, let’s make this week’s Gene of the Week HaKAO1, or more generally any gene coding for the enzyme ent-kaurenoic acid oxidase. These enzymes catalyze a reaction that is required for the synthesis of gibberellins, which are hormones that control plant development. As previously discussed, a loss-of-function mutation in HaKAO1 is associated with an extreme dwarf phenotype in sunflowers [3]. In the model plant Arabidopsis, a double mutant called kao1 kao2 also displays a marked dwarf phenotype [5]. In this case, mutations in both genes are required to see a phenotype; This is an example of genetic redundancy.

The predicted structure of the KAO1 proteins from sunflower and Arabidopsis are very similar, which is unsurprising since their sequences are so similar (and Alphafold predicts structure based on sequence homology). See Figure 6 below.

Figure 6. Top: Alphafold predicted structures of KAO proteins from sunflower (left) and Arabidopsis (right). The Alphafold models used in this figure may be found at: https://alphafold.ebi.ac.uk/entry/D8PJR8 and https://alphafold.ebi.ac.uk/entry/O23051. Bottom: Sequence alignment between sunflower and Arabidopsis KAO1 proteins. The alignment was made using Clustal Omega (https://www.ebi.ac.uk/jdispatcher/msa/clustalo?stype=protein) with default parameters.

Epilogue:

If you’re wondering about the name “Teddy Bear,” it comes from the habit of this variety to produce fluffy looking inflorescences. (Sunflowers are actually made up of many individual flowers, which are collectively called an inflorescence). The flowers on the outer edge of a typical sunflower produce large, showy petals, while the flowers in the middle are much smaller by comparison. In Teddy Bear, the middle flowers also produce large, showy petals, giving the “fluffy” appearance. My Teddy Bear isn’t the most spectacular example of this variety, but the unusual inflorescence phenotype can still be seen in Figure 7 below.

Researchers have actually identified the gene responsible for the inflorescence phenotype of Teddy Bear as HaCYC2c, which codes for a transcription factor that promotes the formation of flowers with large petals [1]. In varieties with the “fluffy” phenotype, the DNA sequence that lies upstream of the protein-coding sequence of the HaCYC2c gene is altered. This causes HaCYC2c to be expressed throughout the whole inflorescence rather than simply in the flowers on the edge… giving us “fluffy” flowers [1]!

Figure 7. The inflorescence of Lemon Queen (left) vs. the inflorescence of Teddy Bear, right.

I should point out that some varieties which have the same “fluffy” inflorescence structure as Teddy Bear, such as “Sungold Tall,” do not have the dwarf phenotype. Hence, the alteration at the HaCYC2c locus cannot explain the short stature of the Teddy Bear sunflower.

Works Cited:

[1] Chapman, M.A., Tang, S., Draeger, D., Nambeesan, S., Shaffer, H., Barb, J.G., Knapp, S.J., & Burke, J.M. (2012). Genetic Analysis of Floral Symmetry in Van Gogh’s Sunflowers Reveals Independent Recruitment of CYCLOIDEA Genes in the Asteraceae. PLoS Genetics 8(3), e1002628. DOI: 10.1371/journal.pgen.1002628

[2] Delen, Y., Palali-Delen, S., Xu, G., Neji, M., Yang, J., & Dweikat, I. (2024). Dissecting the Genetic Architecture of Morphological Traits in Sunflower (Helianthus annuus L.) Genes 15(7), 950. DOI: 10.3390/genes15070950

[3] Fambrini, M., Mariotti, L., Parlanti, S., Picciarelli, P., Salvini, M., Ceccarelli, N., & Pugliesi, C. (2011). The extreme dwarf phenotype of the GA-sensitive mutant of sunflower, dwarf2, is generated by a deletion in the ent-kaurenoic acid oxidase1 (HaKAO1) gene sequence. Plant Molecular Biology 75, 431-450. DOI: 10.1007/s11103-011-9740-x

[4] HeliantHome: A public and centralized database. Home of a comprehensive collection of phenotypes for different Sunflower species. Retrieved August 2, 2025, from: http://www.helianthome.org/

[5] Regnault, T., Davière, J., Heintz, D., Lange, T., & Achard, P. (2014). The gibberellin biosynthetic genes AtKAO1 and AtKAO2 have overlapping roles throughout Arabidopsis development. The Plant Journal 80(3), 462-474. DOI: 10.1111/tpj.12648

[6] Talukder, Z.I., Ma, G., Hulke, B.S., Jan, C., & Qi, L. (2019). Linkage Mapping and Genome-Wide Association Studies of the Rf Gene Cluster in Sunflower (Helianthus annuus L.) and Their Distribution in World Sunflower Collections. Frontiers in Genetics 10, 216. DOI: 10.3389/fgene.2019.00216

[7] Todesco, M., Owens, G.L., Bercovich, N., Légaré, J., Soudi, S., Burge, D., Huang, K., Ostevik, K.L., Drummond, E.B.M., Imerovski, I., Lande, K., Pascual-Robles, M.A., Nanavati, M., Jahani, M., Cheung, W., Staton, S.E., Muños, S., Nielsen, R., Donovan, L.A., Burke, J.M., Yeaman, S., & Rieseberg, L.H. (2020). Massive haploypes underlie ecotypic differentiation in sunflowers. Nature 584, 602-607. DOI: 10.1038/s41586-020-2467-6. GWAS data are available to view at: https://easygwas.biochem.mpg.de/gwas/results/manhattan/view/37d3d070-e7cf-4388-be6d-05be6907d451/