2017: Year in Review

Awkward Botany turns 5 years old this month! 

In the five years since I first introduced myself I have had the pleasure of sharing my writing and photos with thousands of people. Together we have formed a tiny community of nature lovers, botany nerds, and phytocurious folks. It has been fun seeing the audience grow and our interactions increase. The World Wide Web is a crowded and chaotic place, and you can never be sure what will come of the pieces of you that you throw at it. Luckily, my little project has not gone completely unnoticed. The crowd that enjoys it may be small, but it is composed of a solid group of people. Thank you for being one of those people.

If you were following along in 2017, you are well aware that weeds and invasive species have been regular themes. Both of these topics are still obsessions of mine, so while I don’t have plans to continue to saturate the blog with such posts, I will still be writing about them. I’m actually working on a larger project involving weeds, which you can read more about here.

Speaking of which, I have threatened a couple of times now to interrupt my weekly posting schedule in order to make time for other projects. So far that hasn’t really happened, but this year I am fairly certain that it will. It’s the only way that I am going to be able get around to working on things I have been meaning to work on for years. There are also some new things in the works. I think these things will interest you, and I am excited to share them with you as they develop. Once you see them for yourself, I’m sure you’ll forgive the reduced posting schedule.

One thing I have resolved to do this year is learn to draw. I love botanical illustrations, and I have always been envious of the artistic abilities of others. My drawing skills are seriously lacking, but a little practice might help improve that. While it is bound to be a source of embarrassment for me, I have decided to post my progress along the way. So even if you have less to read here, you will at least get to check out some of my dumb drawings. Like this one:

Drawing of a dandelion with help from Illustration School: Let’s Draw Plants and Small Creatures by Sachiko Umoto

One of my favorite things this year has been Awkward Botany’s new Facebook page. With Sierra’s help, we have finally joined that world. Sierra has been managing the page and is the author of most of the posts, and she is doing an incredible job. So if you haven’t visited, liked, and followed, please do. And of course, the invitation still stands for the twitter and tumblr pages, as well.

Lastly, as I have done in the past I am including links to posts from 2017 that were part of ongoing series. These and all other posts can be found in the Archives widget on the right side of the screen. During the summer I did a long series about weeds called Summer of Weeds, the conclusion of which has a list of all the posts that were part of that series. Thank you again for reading and following along. Happy botanizing and nature walking in 2018. I hope you all have a plant filled year.

Book Reviews:

Podcast Review:

Poisonous Plants: 

Drought Tolerant Plants:

Field Trips:

Guest Posts:

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Book Review: Rambunctious Garden

Last month in a post entitled Making the Case for Saving Species, I reviewed an article written by Emma Marris about doing all we can to prevent species from going extinct, even when the approach is not a popular one – like introducing rust resistant genes into native whitebark pine populations. Intrigued by Marris’ words, I decided to finally read her book, Rambunctious Garden: Saving Nature in a Post-Wild Word, which had been sitting on my bookshelf for several months and had been on my list of books to read for at least a couple of years before that. At only 171 pages, Marris’ book is a quick read and comes across as an introduction to some sort of revolution. Its brevity demands future volumes, which are hopefully on their way.

rambunctious garden

The general topic that Marris addresses is how to do conservation work in a world that is riddled with human fingerprints, especially coming from a perspective that human influence is and has been largely negative. What should our goals be? The traditional approach has been to restore natural areas to a historical baseline. In North America, that baseline is usually pre-European colonization. So, we remove introduced species and we use whatever records we have and data we can gather to make natural areas look and function as they did several hundred years ago.

But there are some concerns with this approach. Rewinding time requires massive amounts of money, labor, and time, and if that historical baseline is ever achieved, it will require great effort to keep it there. Also, a number of species have gone extinct and there is no way of replacing them (unless we introduce similar species as proxies), and some species require large areas to roam that even our most spacious parks cannot accommodate. And then there is the challenge of continual change. Anthropogenic climate change aside (which complicates conservation and restoration efforts in serious ways), the earth’s ecosystems are in a constant state of flux, so holding a site to a pre-determined baseline makes little sense when viewed from a geological timescale.

There is another issue – which is in part a semantic one – and that is, we seem to have a distorted view of nature. We like to think of it as being apart from us, away from us, somewhere wild and pristine. Marris writes: “We imagine a place, somewhere distant, wild and free, a place with no people and no roads and no fences and no power lines, untouched by humanity’s great grubby hands, unchanging except for the season’s turn. This dream of pristine wilderness haunts us. It blinds us.”

We are blinded because “pristine” is a myth. Every inch of the globe has been altered in some way by humans – some areas more than others – and disconnecting ourselves from nature in a way that makes it unattainable deters us from the perception that nature can be all around us. Nature is not found only in national parks, nature preserves, and other protected areas, but in our backyards, on our rooftops, along roadsides, in the cracks of concrete, and in farm fields. Nature is everywhere. And if nature is everywhere, then conservation can happen everywhere.

After a brief overview of how we (Americans specifically) arrived at our current approach to conservation and restoration, Marris dives into some new approaches, visiting sites around the world and talking with biologists and ecologists about their work.  She explores rewilding (Pleistocene rewilding even), assisted migration, embracing exotic species, novel ecosystems, and designer ecosystems. The subject matter of each chapter in Marris’ book is worthy of a post or two of its own, but I’ll spare you that and suggest that you read the book. The controversy that surrounds these novel approaches is also worth noting. A few searches and clicks on the internet will lead you to some fairly heated debates about the ideas that Marris puts forth in her book, as well as some criticisms of Marris herself.

Florida torreya (Torreya taxifolia) - a critically endangered tree species native to a tiny corner in the southeastern United States that is not likely to survive the coming decades in the wild without assisted migration.

Florida torreya (Torreya taxifolia) – a critically endangered tree species native to a tiny corner in the southeastern United States that is not likely to survive the coming decades in the wild without assisted migration. (photo credit: www.eol.org)

My view as an outsider – that is, one without a high level degree in ecology and lacking years of experience working in the field – is that the tools and methods outlined in Marris’ book are worth exploring further. Certainly, each natural area must be approached differently depending on the conditions of the site and the goals of the managers. [Marris offers a great overview of some goals to consider in her last chapter.] Ultimately it is up to people much smarter and more experienced than I to sort it all out. But I heartily encourage thinking outside of the box…for whatever it’s worth.

And that brings me to what I loved most about the book. Controversy aside, Marris’ clarion call for a paradigm shift is a welcome one. Nature is all around us, and regardless of what land managers and the powers that be decide to do with large tracts of land “out there,” every individual can find purpose and beauty in the nature that surrounds them, whether it be the street trees that line our neighborhoods or the vacant lot growing wild with weeds down the street. We can decide to let our yards go a little feral, to plant some native plants, to encourage wildlife in urban areas, and to even do a little assisted migration of our own by planting things from nearby regions just to see how they will do in our changing climate. In short, we can garden a bit more rambunctiously. And we should.

This is how Marris puts it:

If we fight to preserve only things that look like pristine wilderness, such as those places currently enclosed in national parks and similar refuges, our best efforts can only retard their destruction and delay the day we lose. If we fight to preserve and enhance nature as we have newly defined it, as the living background to human lives, we may be able to win. We may be able to grow nature larger than it currently is. This will not only require a change in our values but a change in our very aesthetics, as we learn to accept both nature that looks a little more lived-in than we are used to and working spaces that look a little more wild than we are used to.

Read a short interview with Marris about her book here, and listen to a discussion with her on a recent episode of Out There podcast.

Botany in Popular Culture: Black Orchid

Black Orchid coverBlack Orchid is a minor character in the DC Comics universe. She is a superhero with a troubled past, and although she first began appearing in comic books in 1973, her origin was a mystery until 1988 when Neil Gaiman wrote his 3 part mini-series entitled, Black Orchid, revealing that she was a plant-human hybrid created by Dr. Philip Sylvain after combining the DNA of Susan Linden-Thorne with the DNA of an epiphytic orchid.

Curiously, in order to reveal Black Orchid’s origins, Gaiman has the namesake of his series killed off within the first few pages. A master of disguise, Black Orchid is following her standard modus operandi of impersonating someone in order to infiltrate enemy headquarters. In this case she is pretending to be a secretary in Lex Luthor’s employ. While sitting in on a board meeting in which the activities of Luthor’s crime ring are being discussed, her secret identity is revealed, which leads to her being tied to a chair and shot through the head. The bullet doesn’t kill her though since invulnerability to bullets is one of her superpowers (along with flight, super strength, shape shifting, and others). However, the building is also set on fire, and ultimately all that is left of Black Orchid at the end of the night are some charred plant remains.

The story can’t end there though, so as Black Orchid goes up in flames, two of her clones emerge from flower buds in Dr. Sylvain’s greenhouse. They aren’t sure what they are at first. They have some of Susan’s memories but don’t know what to make of them. One of them is a child called Suzy, and the other is an adult who eventually gets the name Flora Black. They find their way to Dr. Sylvain who tells them the story of how they and the original Black Orchid came to be.

Dr. Philip Sylvain tells the Black Orchid clones about how he

Dr. Philip Sylvain tells the Black Orchid clones about his childhood with Susan Linden.

Susan was Dr. Sylvain’s childhood friend. They spent lots of time in the garden together learning about plants and growing things. But Susan was abused regularly by her father and eventually ran away as a teenager. Dr. Sylvain didn’t see her for many years, and in the meantime grew up and became a botanist. At university, Dr. Sylvain studied with Jason Woodrue, Pamela Isley, and Alex Holland, each of whom went on to become plant-human hybrids of some sort (Floronic Man, Poison Ivy, and Swamp Thing respectively). Dr. Sylvain had ambitions of making “people of plants” as part of a plan to save a dying earth. His ambitions remained a dream until Susan returned.

Dr. Sylvain's friends from university who later became plant-hybrid heroes and villians.

Dr. Sylvain’s friends from university who later became notorious plant-human hybrids.

Susan was running away again – this time from her abusive husband, Carl Thorne, who worked for Lex Luthor as an arms dealer. Thorne was in trouble with the law and was ultimately put on trial for his crimes. Susan came to Dr. Sylvain seeking refuge. She was set to testify against her husband, but before she could do that, Thorne killed her. Dr. Sylvain then used Susan’s DNA to create the crime fighting, superhero, Black Orchid.

Coincidentally, as the original Black Orchid is being killed and the two new Black Orchids are emerging, Thorne is finishing his prison sentence and being released. He first goes to Luthor to try and get his job back, but is turned away. Next he goes to Dr. Sylvain’s house where he discovers the newly emerged Black Orchids. He alerts Luthor, who sends a team to hunt down the “super-purple-flower women” and bring them back to the lab for “examination and dissection.” The rest of the series details the Black Orchids’ mission to make sense of who they are and what their purpose in life is while simultaneously contending with Luthor’s men (and Thorne) who are out to get them. Flora Black meets with Batman, Poison Ivy, and Swamp Thing along the way, filling in her origin story and gaining instruction and insight about her future as a superhero.

Gaiman is a popular, prolific, and well-respected author; however, this is the first of his books that I have read. I was impressed by his storytelling and appreciated the departure from the typical superhero vs. villain narrative. Dave McKean did the artwork for this series, which was an excellent decision as his work is also quite atypical for the genre. His illustrations gave the book a mystical feel as the panels altered from standard storytelling sequences to abstract, fantasy pieces.

This Black Orchid storyline continued for several issues after Gaiman’s three part mini-series without Gaiman as the author. Flora Black was eventually killed off. A new version of the Black Orchid character currently appears in the ongoing Justice League Dark series.

Alba Garcia (aka Black Orchid), a member of Justice League Dark

Alba Garcia (aka Black Orchid), a member of Justice League Dark

You can read more about Black Orchid on her Wikipedia and Comic Vine pages.

Botany and Everyday Chemistry

What’s not to love about plants? They provide us with oxygen, food, medicine, fuel, fibers, and countless other things. They help filter groundwater and sequester carbon. They beautify our landscapes and communities. They provide habitat for wildlife and help reduce soil erosion. And the list goes on.

But there is more to plants than meets the eye. There is something deeper within – at their cellular and molecular levels – that is just as worthy of our fascination and appreciation as the blooms that beautify our yards and the fruits that fill our tables, and that is the abundant and diverse world of chemical compounds present in the botanical kingdom.

But how does one gain an understanding and appreciation for such a subject. Luckily, there is a blog for that. It’s called Compound Interest. Authored by UK chemistry teacher, Andy Brunning, Compound Interest explores the “chemistry and chemical reactions we come across on a day-to-day basis.” Much of what Andy writes about doesn’t have anything to do with plants – fireworks, bacon, gunpowder, snowflakes, etc. – but a sizeable portion of his posts do (evidenced particularly by the Food Chemistry category). For example: Did you know nutmeg is hallucinogenic? Have you ever wondered why avocados turn brown so quickly? Why is it that some people have such a strong aversion to cilantro (aka coriander)? What makes coffee bitter, chili peppers spicy, and catnip so attractive to cats?

These and so many other questions are answered by Andy in a fun and approachable way. One thing that makes Compound Interest so approachable is the use of infographics to tell the stories and explain the science. Each post is accompanied by an infographic featuring photos of the subject, structural formulas of the chemicals, and short descriptions.  For example, this infographic explains why beets are red and why our urine turns red after eating them:

Chemistry-of-Beetroot

The infographics can also be downloaded as pdf files, like this one that explains the chemistry behind the smell of fresh-cut grass.

In this manner, the images and files can be easily shared with others. In fact, Andy encourages this practice, provided that the originals are not altered and that Compound Interest is given proper credit. He is particularly interested in seeing his infographics used in a classroom setting. Read more about the content usage guidelines here. Produced by someone who is obviously passionate about chemistry, these posts and graphics are meant to educate and excite people about everyday chemistry both in the botanical world and beyond.

Speaking of Food: A Recap

The theme for the past 15 posts has been the October 2014 Special Issue of American Journal of Botany, Speaking of Food: Connecting Basic and Applied Plant Science. After a brief introduction to the issue, I spent the next 14 posts (spanning a period of 5 weeks) reading and writing summaries of each of the 17 articles. If you actually read every post, you are a champion in my eyes, and I probably owe you a prize of some sort. And even if you just read one or two, thank you, and I hope you found value in what you read.

I have to admit that it was kind of a grueling process. Many of the articles, along with being lengthy, included high level discussions that were beyond my current understanding, especially concerning topics like genetics, genomics, and phylogenetics. I learned a lot while reading them, but I am still far from truly grasping many of the concepts. For that reason, I did not feel completely comfortable writing summaries of some of these discussions. I made an effort not to misrepresent or oversimplify the research, but I can’t say for sure that my attempts were always successful. I welcome any criticisms, corrections, complaints, or comments in this regard, and I am open to making edits or updates to any of the posts as necessary. I consider this blog my learning platform, as well as a place to share my phyto-curiosity. Perhaps you find it a place for learning, too?

The main purpose of this post is to provide a Table of Contents for the last 14 posts, something that will make it easier to navigate through this series without having to scroll through each post. If you are interested in reading the entire series (again, you’re a champion), you can access them all in order here by clicking on the titles. Otherwise, you can pick and choose whatever topics interest you the most.

  • On the Origins of Agriculture – A deep dive into plant domestication and the beginnings of agriculture, including the revision of theoretical approaches to thinking about the history of plant domestication and a discussion of emerging methods and tools for exploring early domestication and emerging agriculture.
  • The Legacy of a Leaky Dioecy – Does pre-Colombian management of North American persimmon trees explain why non-dioecious individuals are found in an otherwise dioecious species?
  • Dethroning Industrial Agriculture: The Rise of Agroecology – The environmentally devastating effects of industrial agriculture can and must be replaced by a more sustainable, ecologically-focused from of agriculture. This will require reforming our economic system and rethinking our “one size fits all” approach to scientific research.
  • An Underutilized Crop and the Cousins of a Popular One – Safflower, an underutilized oilseed crop, could be improved by introducing genes from wild relatives. Soybean, a very popular and valuable crop, could also be improved by introducing genes from its perennial cousins.
  • Carrots and Strawberries, Genetics and Phylogenetics – An exploration of the genetics and phylogenetics of carrots and strawberries. Better understanding of their genetics will aid in crop improvements; better understanding of their phylogenetics gives us further insight into the evolution of plants.
  • Exploring Pollination Biology in Southwestern China – A fascinating look at the pollination biology of edible and medicinal plants in southwestern China, revealing significant gaps in scientific understanding and the need for conservation and continued research.
  • Your Food Is a Polyploid – Polyploidy is more prevalent in plants than we once thought. This article examines the role of polyploidy in crop domestication and future crop improvements.
  • Tales of Weedy Waterhemp and Weedy Rice – How agriculture influenced the transition to invasiveness in two important weed species.
  • Cultivated Sunflowers and Their Wild Relatives – An investigation into the flowering times of wild sunflowers reveals potential for improvements in cultivated sunflowers.
  • The Nonshattering Trait in Cereal Crops – Is there a common genetic pathway that controls the shattering/nonshattering trait in cereal crops?
  • Apples and Genetic Bottlenecks – Domestication generally leads to a loss of genetic variation compared to wild relatives, but apples have experienced only a mild loss. That loss may increase as commercial apple production relies on fewer and fewer cultivars.
  • Improving Perennial Crops with Genomics – The nature of perennial crops can be an impediment to breeding efforts, which makes the introduction of new perennial crop varieties both time consuming and costly. Advances in genomics may help change that.
  • Using Wild Relatives to Improve Crop Plants – Crop plants can be improved through the introduction of genes from wild relatives. They could potentially experience even greater improvement through systematic hybridization with wild relatives.
  • Developing Perennial Grain Crops from the Ground Up – Some of the environmental issues resulting from agriculture could be addressed by switching from annual to perennial grain crops, but first they must be developed from wild species.
A small harvest of sweet potatoes (Ipomoea batatas ' Hong Hong') from this year's backyard mini-farm. Ipomoea batatas ' Hong Hong.'

A small harvest of sweet potatoes (Ipomoea batatas ‘ Hong Hong’) from this year’s backyard mini-farm.

If I had to pick a favorite article in this issue it would be Think Globally, Research Locally: Paradigms and Place in Agroecological Research (Reynolds et al.). I know I said it in the post, but this article really sums up the reasons why this special issue of AJB is so important. Humans are incredibly resourceful, creative, and resilient, and as we have spread ourselves across the globe and grown our population into the billions, we have found ways to produce enormous amounts of food relatively cheaply. Frankly, the fact that anyone is going hungry or dying of starvation is shameful and appalling as there is plenty of food to go around…for now. But we are doing a lot of things wrong, and the earth is suffering because of it. If the biosphere is in trouble, we are all in trouble. Thus, we are overdue for some major shifts in the way we do things, particularly agriculture as that’s what this series of posts is all about. I advocate for science-based sustainable agriculture, and I am hopeful, thanks to this issue of AJB and other signs I’ve seen recently, that we are moving more in that direction. I’ll step off my soapbox now and leave you with an excerpt from the article by Reynolds, et al.

“There is increasing recognition that the current industrial model of agricultural intensification is unsustainable on numerous grounds. Powered by finite and nonrenewable stores of fossil fuels over the last 200 years, humans have come to see themselves, their technology, and their built environments as controllers of nature rather than interdependent with it, even as our activities threaten to exceed planetary boundaries of resilience in multiple environmental dimensions, such as climate, biodiversity, ozone, and chemical pollution. … In the ‘full world’ we now live in, continuing to use high input, highly polluting methods of food production to support continued economic growth is counterproductive to achieving food security. Continued growth of population and per capita consumption on a finite planet fails to meet the basic requirement of sustainability, that of meeting needs within the regenerative and assimilative capacity of the biosphere. And prolonging the shift to a sustainable economic paradigm risks a harder landing.”

Using Wild Relatives to Improve Crop Plants

This is the thirteenth in a series of posts reviewing the 17 articles found in the October 2014 Special Issue of American Journal of Botany, Speaking of Food: Connecting Basic and Applied Science.

Back to the Wilds: Tapping Evolutionary Adaptations for Resilient Crops through Systematic Hybridization with Crop Wild Relatives by Emily Warschefsky, Varma Penmetsa, Douglas R. Cook, and Eric J. B. von Wettberg

The nature of domestication involves the narrowing of genetic diversity through a series of crosses and selections that results in organisms well suited for particular environments and/or purposes. In the short term, this arrangement seems to suit our needs, that is until the climate shifts, novel pests and diseases invade, agricultural soils become degraded, or some other calamity ensues. Then we must select a new form to take the place of the old one that is no longer suitable. Additionally, the varieties currently in use may be doing well within their current parameters, but their performance may be found lacking if placed in different environments or grown in alternate systems, such as one that relies on fewer petrochemical inputs.

The wild relatives of crop plants have a long history of being used in breeding programs to provide specific traits for improving domesticated varieties. Interest in this has increased thanks to technological advancements (such as marker-assisted selection and genomic selection) and the greater availability of germplasm. Introgression (the transfer of genes from one species to another through hybridization and repeated backcrossing) using crop wild relatives has mainly been aimed at introducing traits like resistance to specific pests and diseases, tolerance of certain abiotic stresses, and greater yields. In other words, crop wild relatives are typically screened for a few main traits that might be useful in breeding programs, neglecting the possibility that the introgression of a larger suite of traits may be beneficial long-term.

This article discusses the possibility of using “crop wild relative collections that [have been] systematically built to represent the range of adaptations found in natural populations” to improve crop plants. By using these “purpose-built populations that are hybrids between crops and their wild relatives,” crop plants introgressed with “full sets of wild diversity” will be better adapted to a wide variety of environments, soils, climates, and agricultural systems. In order to “illustrate the gains that are possible,” the authors review published studies of hybridization (both naturally occurring and human mediated). They then “propose a multi-step framework for utilizing naturally occurring variation in wild relatives of crops.”

Grapefruit (Citrus x paradisi) - A hybrid between sweet orange (Citrus sinensis) and shaddock (Citrus maxima) that "occurred far beyond the region of domestication and rather recently [the 18th centruy]." (photo credit: wikimedia commons)

Grapefruit (Citrus x paradisi) – A hybrid between sweet orange (C. sinensis) and shaddock (C. maxima) that “occurred far beyond the region of domestication and rather recently [the 18th century].” (photo credit: wikimedia commons)

Hybridization can occur between two individuals of different cultivars, varieties, subspecies, species, genera, etc. The genetics of the resulting offspring is a combination of the two parents, and depending on the circumstances, a hybridization event “can have drastically different consequences.” For this reason, “hybridization is thought of as both a creative and a restrictive force in evolution.” It is, however, “the potential for the production of novelty that makes hybridization such an intriguing – and potentially useful – phenomenon.”

In their discussion of hybridization between crops and their wild relatives, the authors reveal some “obstacles that limit the use of wild relatives in breeding programs.”

  • Poor Agronomic Performance – “Crop wild relatives often lack important domestication traits.” They may have shattering pods, irregular germination timing, or phenologies that inhibit their use in certain regions.
  • Poor Representation in Germplasm Collections – “Only 2-6% of international germplasm collections are of crop wild relatives.” There are some crop wild relatives that are well-represented, but others have been “poorly collected” or “almost ignored,” and some crops still “lack well-identified wild relatives.” One reason for this disparity is that a large number of these plants “occur in geopolitically unstable areas where collection has long been complicated.”
  • Unpredictability of Phenotypes – “Phenotypes of wild individuals are often assessed in agricultural settings, a largely uninformative practice when the overall wild phenotype is specifically adapted for fitness in the wild but not cultivated settings.” This makes for an inaccurate comparison with domesticated varieties, so when “crop-wild hybrids” are formed, phenotypes are hard to predict. Backcrossing is necessary in order to recover the “essential crop phenotype” while capturing the desired traits of the wild relative.

The authors also highlight the need for conservation of crop wild relatives, as “these species are nearly universally threatened.” The catalog of threats to their survival is similar to so many other threatened species: the loss, fragmentation, and degradation of habitats, climate change, invasive species, and over-harvesting (“in the case of medicinally and pharmaceutically useful species”). One threat, perhaps ironically, is agricultural crops crossing with nearby wild relatives, especially where transgenic genes in crops are being transferred to wild populations. In order to better realize the potential that crop wild relatives have in improving domesticated varieties, they must first be protected in their natural habitats.

Desert sunflower (Helianthus deserticola) - One of three hybrid species born of H. annuus and H. petiolaris, "highlighting the expanded potential of hybrid species...through colonization of extreme habitats where neither parental species can survive." (photo credit: www.eol.org)

Desert sunflower (Helianthus deserticola) – One of three hybrid species born of H. annuus and H. petiolaris, “highlighting the expanded potential of hybrid species…through colonization of extreme habitats where neither parental species can survive.” (photo credit: www.eol.org)

The authors propose a 5 step plan for systematic utilization of crop wild relatives in agricultural breeding programs. The steps include building a comprehensive collection of crop wild relatives, sequencing their genomes, creating purpose-driven hybrid populations between wild relatives and crop plants, developing a predictive network of genotype-phenotype associations, and deploying identified phenotypes into crop breeding efforts. This article is one of the open access articles in this issue. If you are interested in this topic, including this 5 step plan, I encourage you to read the article to learn more. 

The Nonshattering Trait in Cereal Crops

This is the tenth in a series of posts reviewing the 17 articles found in the October 2014 Special Issue of American Journal of Botany, Speaking of Food: Connecting Basic and Applied Science.

Morphological Diversity and Genetic Regulation of Inflorescence Abscission Zones in Grasses by Andrew N. Doust, Margarita Mauro-Herrera, Amie D. Francis, and Laura C. Shand

Seed dispersal is a key aspect of reproduction in plants. Producing seeds requires large amounts of energy and resources, and if the seeds don’t find their way to a suitable environment where they can germinate and grow, then it may be all for naught. There are several modes of seed dispersal (wind, gravity, water, animals, ballistics), and each plant species has its own story to tell in this regard. However, one commonality that most all seed dispersal stories share is “disarticulation [separation] of the seed or fruit from the body of the plant via means of the formation of an abscission zone.”

Seeds are typically dispersed inside fruits, and attached to the fruits may be other plant structures (such as parts of the inflorescence or, in the case of tumbleweeds, the whole plant). The entire dispersal unit (seed, fruit, etc.) is known as a diaspore. In the grass family, a fruit is called a caryopsis. It is a unique fruit because the fruit wall is fused to the seed, making it difficult to distinguish between the two. Methods of disarticulation in grasses are diverse, with diaspores varying greatly in their sizes and the plant parts they contain. Below is a figure from this article showing this diversity. Abscission zones are depicted using red dotted lines.

Domesticated crop plants do not exhibit the same levels of disarticulation that their wild relatives do. This is because “nonshattering forms” were selected during early stages of domestication due to their ease of harvest. Today, all domesticated cereal crops are nonshattering, and all began by selecting “a nonshattering phenotype where the grain [did] not fall easily from the inflorescence.”  However, the wild relatives of cereal crops, “as well as grasses as a whole, differ widely in their manner of disarticulation [as indicated in the figure above].” A mutation in the genes that control abscission is what leads to nonshattering phenotypes. Because all domesticated cereal crops began as nonshattering mutants, the authors of this study were interested in investigating whether or not there is a common genetic pathway across all cereal crops and their wild grass relatives that controls the abscission trait.

The “genetic control of loss of shattering” is important to those interested in domestication, thus it “has been studied in all major crops.” Some of these studies suggest that there is a common genetic pathway that controls abscission in cereal crops, while others suggest there may not be. The authors of this study suspect that “there is potential for considerable genetic complexity” in this pathway, and so before we can determine “the extent to which there are elements of a common genetic pathway,” we must first develop “a better understanding of both diversity of disarticulation patterns and genetic evidence for shared pathways across the grasses.”

In an effort to begin to answer this question, the authors used herbaria vouchers to analyze “morphological data on abscission zones for over 10,000 species of grasses.” They also reviewed published scientific studies concerning the genetics of disarticulation in grasses and cereal crops. They determined that “the evidence for a common genetic pathway is tantalizing but incomplete,” and that their results could be used to inform a “research plan that could test the common genetic pathway model more thoroughly.” Further studies can also “provide new targets for control and fine-tuning of the shattering response” in crop plants, which could result in “reducing harvest losses and providing opportunities for selection in emerging domesticated crops.”

Foxtail millet, Setaria italic (photo credit: www.eol.org)

Foxtail millet (Setaria italica), a widely cultivated species of millet, has “shattering genes” similar to those found in sorghum and rice (photo credit: www.eol.org)