Better Know a Scientist: Weed Scientist Dr Lynn Sosnoskie

People: we’re in for a special treat today. One of my favorite tweeple, Dr Lynn Sosnoskie, has graciously accepted a Q&A for “Better Know a Scientist”. Dr Sosnoskie is a scientist at UC Davis’ Plant Science Department where she does research on weed control. She has a PhD in weed science from Ohio State and has done research at University of Wisconsin, as well as the University of Georgia.

I did a bit of crowd-sourcing and asked on my private Facebook profile what questions my friends and family would like to ask, and there were some excellent recommendations. My comments throughout reflect the fact that we installed fake grass in a good chunk of our yard after two trucks full of mulch created a weed-free, yet visually unappealing and fire-hazardous yard.  So here we go!

Q: Weed research seems to be a fairly random field to study. I don’t think I’ve ever met a kid or high-school student who dreams of becoming a weed researcher when they grow up. What led you to this field?

Dr Lynn Sosnoskie

A: It’s a long and random story, but I’ll try to sum it up nicely. As a biology major (during my undergraduate degree) we took a Botany class field trip to Longwood Gardens in Kennett Square, Pennsylvania. I fell in love with the place and, more importantly, fell in love with plant science. Following my graduation, I was lucky enough to intern at Longwood and a few other gardens/arboretums in the greater Philadelphia area. While attending a pest control lecture on dandelions, I just knew that I wanted to go further into the plant protection arena. After a brief detour (my MSc. in Plant Pathology), I was fortunate to get a research assistantship in a weed ecology lab at Ohio State, where I earned my PhD. I enjoyed my pathology years, but I was just always more interested in plant-plant interactions as opposed to plant-pathogen interactions.

[Biochica’s note: if only everyone was inspired by dandelions instead of being filled with rage...]

Q: What are you currently researching?

A: I have quite a few projects underway. Firstly, I am finishing up some studies looking at seed production in hairy fleabane (Conyza bonariensis) following failed herbicide applications. Hairy fleabane is a common weed in our orchard and vineyard systems in California  and many plant populations have developed resistance to glyphosate (which has been the most frequently applied herbicide in perennial systems). Hairy fleabane is a real bane to growers because it produces LOTS of wind-dispersed seed, which are responsible for both new and continuing infestations [Biochica’s note to Lynn: I see what you did there… “The Hairy fleabane is a real bane”... Awesomeness!!]. To return to my earlier statement about seed production following herbicide failures, I am interested in understanding how the plants that escape weed control efforts might affect the development of weed populations.

I am also looking at the growth and development of junglerice (Echinochloa colona), which is also a pest of California orchard systems (almonds, walnuts, pistachios etc..., under differing environmental and disturbance conditions to look at its potential to invade other cropping systems. A chunk of my time is also spent researching the biology, ecology and management of field bindweed (Convovulus arvensis), which is a significant problem in processing tomatoes.

Q: Why do some herbicides develop weed-resistant pests more quickly than others?

A: The development of resistance is a function of many different factors...the phenomenon really should be looked as an interaction between the weed, the cropping system, AND the herbicide. The simple answer to your question is ‘overuse of certain products in time and space’ and the simple solution, in turn, is that we should avoid using a single herbicide mechanism of action, exclusively, to control weeds. Yes, we have to ensure that we use our herbicides responsibly (see this post by Dr. Andrew Kniss (University of Wyoming)), but we also need to understand the current constraints on our cropping systems that might limit our abilities to diversify (see this post, also by Andrew Kniss). And let’s not forget the weeds, themselves. Certain biological characteristics appear to be more commonly associated with the development of herbicide resistance. Dr. Jodie Holt (University of California, Riverside) and some colleagues published an interesting paper in PLOS ONE looking at the ‘Taxonomic and Life History Bias in Herbicide Resistant Weeds’. They found that evolved resistance is more common in certain plant families (i.e. the Amaranthaceae, Brassicaceae, and Poaceae) than in others. They also reported that annual weed species were found more often in the list of weeds with evolved herbicide resistance, suggesting that the length of a species’ life cycle is a contributing factor. Although they didn’t have enough data to link other traits (i.e. seed production or outcrossing rate) to the development of herbicide resistance, many other sources have suggested that these characteristics can facilitate the evolutionary process.

[Biochica’s note to Lynn: does this mean that I can ask the spouse to go kill the weeds as soon as possible, because if he doesn’t they’ll evolve to become herbicide tolerant? Don’t answer that! That’s what I’m going to tell him...]

Q: What beneficial weeds do we often overlook when thinking about weeds?

A: I think the biggest beneficial weed on (almost) everyone’s mind is milkweed, which is a host for monarch butterflies. Many people might ask themselves: “Should I be actively planting milkweed on my property?” Only you can answer that question. Talk to your local extension agents or master gardeners if this species is an appropriate addition for your yard. At the very least they can direct you to the appropriate resources.

Q: How often have you had to say “No, I’m not *that* kind of weed scientist”? Do you have a poster of Cheech in your office?

A: A lot. Whenever one of my professional societies (California Weed Science Society, Western Weed Science Society, Weed Science Society of America) has a meeting somewhere, and people see our name badges, there is the inevitable “Wow. You must have some great parties, you know what I mean.” I do know what they mean and, sorry to say, they are likely to be sorely disappointed if they ever found out the truth about our parties (we just talk about weeds, the ‘boring’ ones). I do have a cheeky magnet from the city of Weed, California, on my filing cabinet, though.

[Biochica’s note: yeah… I’m going to need video footage of the next “Weed Science Society of America” conference. But I’ve got a nagging suspicion that it’s a “what happens at the conference, stays at the conference” kind of event *Wink, wink* ]

Q: Currently, there’s a lot of buzz surrounding “chemicals” in and on our food. Do you think that a world without herbicides is possible?

A: Is it possible? Sure. Don’t forget we farmed without synthetic, exogenous herbicides for millennia. And, despite what many might think, numerous weed scientists are looking at non-chemical strategies for weed control. For instance, in Georgia, we had a serious problem with glyphosate-resistant Palmer amaranth (Amaranthus palmeri). I worked with Dr. Stanley Culpepper (University of Georgia) to investigate the use of a fall tillage (soil inversion to a depth of 12 inches) coupled with a rye cover crop that we killed in the spring and used as a mulch to suppress Palmer seed germination/seedling emergence. Using  this strategy, we were able to reduce our in-crop Palmer amaranth densities by 90% or more. Now, we weren’t completely free of herbicides, but we did reduce the selective pressure that we put on them. As another example, Drs. Steve Fennimore and David Slaughter (University of California, Davis) are doing some really great work to develop automated weeding machines to use in high-value specialty crops (which have a limited number of herbicides available to them). However, with respect to your original question (Do you think that a world without herbicides is possible?), I’m going to have to say no… at least not at this time. We (weed scientists) are working with growers to diversify their weed production practices, but many do not have the money, the labor pool, the infrastructure, etc that will allow them to abandon herbicide use completely. Herbicides are a tool and our goal is to help growers use as many tools as are appropriate in their systems both safely and effectively.

[Biochica’s note: The Food Babe disagrees with you: no amount of chemicals is acceptable. Ever. Your nuanced explanation with references carries little weight when the Food Babe has spoken on the topic.]

Q: What are some of the more effective ways to get rid of weeds?

Lynn's picture of Bindweed

A: The answer to that question will depend on more than a few criteria, such as: what is the weed you are trying to get rid of, where is the weed located, and how hard do you want to work at getting rid of it, to name just a few. The most effective weed management strategies that might be employed in one’s backyard may be very different from those used by a commercial grower. For example, in a small patio space, hand-weeding is a viable strategy...the same is not true for thousands of acres of soybean. But all weed control strategies can be grouped into a few general categories: 1) exclusion or preventative measures (i.e. preventing weeds from entering your system), 2) physical disturbance (i.e. hand-weeding and cultivation), 3) obstruction (i.e. the use of a mulch or other time of barrier), 4) cultural practices (i.e. using crop rotation to manage weed populations), 5) biological control (i.e. allowing sheep to graze on edible weeds), and 6) chemical control (i.e. using a synthetic or organic herbicide to disturb plant growth and development). Ideally, we would encourage anyone/everyone to make use of as many strategies as are appropriate for their system. And, remember, you don’t have to figure this all out by yourself; your state extension personnel are there to help you with these kinds of decisions.

[Biochica’s note to the spouse: there are weed control strategies other than mulching!!]

Q:  Are there any new, more selective (and perhaps safer) herbicides in the pipeline?

A: I always tell my growers that they shouldn’t rely on the introduction of a new herbicide for weed control. We saw an abundance of products being released in the 1970’s and 1980’s, however the number of new discoveries has certainly plateaued. I don’t work for a chemical company, so I don’t know what the research pipelines look like, currently. If I had to speculate, I would suggest that the corporations are putting more money into crop trait development and big data. Assuming that we aren’t going to be getting a new herbicide product anytime soon, I think that we need to become smarter about how we use the ones that are available to us. For example, improved knowledge about weed biology and ecology will helps target weeds at the more vulnerable parts of their life cycles; in doing so, we will maximize the use of our herbicide tools and, hopefully, use them less frequently.

[Biochica’s note to Lynn: chemical companies should get into the astroturf business. Best weed-control system in California!!]

Q: Dr Andrew Kniss wrote an awesome post looking into that meme that I keep seeing on Facebook, about how vinegar+soap is “better” than Round-Up. He concludes that Vinegar+soap has a more toxic profile and is also more expensive. What often heard myth about weed science would you like to dispel if you could?

A: That we are only interested in applying herbicides. Yes, herbicides are useful tools, but weed scientists study/evaluate a wide range of management strategies. For example, I have worked, and still work with herbicides, but I have also been involved in other research projects looking at the effects of tillage, crop rotation, and cover crops on weed suppression and changes in weed community composition and structure. My colleagues at UC Davis and other institutions are engaged in many fascinating projects designed to further our understanding of weed biology and ecology, resistance evolution, and precision agriculture with respect to weed control.

[Biochica’s note to Lynn: my backyard is open to UC Davis plant community to study the impact of concrete and astroturf on weed development. I've actually had a few weeds make their way through!! I have created superweeds!!]

Q: You are stuck on an island and about to go insane from boredom. A genie suddenly appears and gives you the following choices (you have to pick one): a) an iPad with infinite battery life where your only App is Twitter and it's locked so you can only follow Nassim Taleb or b) A copy of "Seeds of Deception" by Jeffrey Smith. Which do you pick?

A: Taleb’s twitter feed. Although I disagree with his stance on GMOs, and often find him to be rude, there is interesting dialogue to be had.

GMO labeling arguments are not exclusive to GMOs

When discussing labeling, there are many different reasons to want GMOs labeled: some people want to know if something's a GMO because they want to avoid pesticides, some people want to avoid food produced by Monsanto, etc. The issue with every single argument is that it's never exclusive to GMOs. I made the following infographic to outline the more common labeling arguments I've heard, as well as a non-GMO example that matches the criteria set out for that argument. This expands on my Facebook post (you can follow me on my new page!)

Click on image for full size

1) GMOs are made in a lab (i.e. they are not "natural"): this also holds true for many polyploids, such as seedless watermelons. Many mutagenic crops are also made in a lab (to learn more about different crop modification techniques, see this post). So if "unnaturalness" is one's reason to label GMOs, then many other non-GMO crops, include many that are accepted under the USDA's organic label, should also be labeled. 

2) GMOs use herbicides: many argue that GMOs made to resist "toxic" levels of herbicides should be labeled. The toxicity of the herbicides and the amounts used are a subject for a separate post altogether, but when it comes to labeling, there are mutagenic, non-GMO crops that are also made to resist herbicides, particularly Clearfield crops made by BASF which resist imidazolinone herbicides. So if labeling proponents want crops that use herbicides to be labeled, many non-GMOs will have to be labeled as well.

3) GMOs are patented: as I've outlined in the past, many non-GMO crops, including decorative plants and crops approved for use in organic farming, are patented. For a partial list of patented crops, see here. So wanting GMOs labeled to avoid patented crops should result in many, many non-GMOs being labeled, too. 

4) GMOs have genes from other species: not only do sweet potatoes have bacterial genes, but these were introduced using the same bacteria that scientists have harnessed when creating a new transgenic crop. At the same time, DNA from viruses are found throughout most genomes, including our own. 

5) GMOs are made by Monsanto: if you want GMOs labeled because Monsanto makes them, then some organic crops should also be labeled. Plus, what about all the GMOs that are not made by Monsanto? The non-browing Arctic Apple was made by small company in Canada.

6) GMOs make their own pesticides: all plants make their own pesticides. For example, wheat produces an insecticide known as DIMBOA (wheat is not considered a GMO). This post gives an overview of pesticides naturally produced by quinoa. 

Finally, there's the "right to know". But, again, what is it that you want to know? If you want to know what method was used to generate the crop from which an ingredient was derived, then why not mutagenic crops? Why not polyploids? Why not protoplast fusion? What is it about the method of transgenesis that has driven you to demand your "right to know" that didn't apply in the past for any of these other crop breeding methods? Feel free to comment below.

Updated on January 5th: The graphic had a typo, so I've swapped it with a corrected version.

Transgenic Crops and Traits

So, the spouse has often complained that I don't have a post with an overview of what transgenesis means and the transgenic (GMO) crops themselves. They're scattered throughout the history of this blog, but not in a single place.

Transgenesis means taking a gene (or genes) from one species and sticking it into another. Unlike another process known as cisgenesis, transgenesis involves adding genes from a species that is sexually incompatible with the organism in question. Transgenesis is like taking a gene from a pomegranate and adding it to a Granny Smith apple. In contrast, cisgenesis is like taking a gene from a Red Delicious apple and adding it to a Granny Smith apple. For transgenesis, the species doesn't even have to be a plant: you can take a gene from an animal or bacteria and add it to a crop/plant or viceversa.

What does this mean? To explain, I have to go to the beginning: the working units within any cell are proteins. Proteins are made up by linking together amino acids in a given sequence. The exact amino acid sequence is defined in the cell's DNA; the DNA blueprint for a specific protein is known as a gene for that protein. In general, one gene encodes for one protein (of course, there are exceptions). Since there are thousands of proteins, there are thousands of genes. We're still figuring out what different genes/proteins accomplish.

Spouse: I think that you've been surprised by the fact that I can't just "make up" a protein. I wish!!! No, biotech still isn't at the point where I can say "I'm going to invent a DNA sequence that's a blueprint for a protein that will make the plants absorb more water". That would be AWESOME. The best we can do right now is to look in nature at the plants/animals/bacteria that have the trait that we want, find out what protein accomplishes that task, and then use it in transgenesis. The reason why this is important in discussions about transgenesis is that the proteins that have been added to GMOs are already in nature.

In transgenic crops, they've taken one or more genes from different species and added them to the plant's DNA so that you have new genes/proteins in the plant. That brings us to the main point of this article: what are some of the more popular genes/proteins that have been added to commercial transgenic crops or GMOs.

Transgenic proteins currently used in US agriculture can be split into 3 broad categories: herbicide tolerance, insect resistance and disease resistance. Here are some of the traits used in each category (NOTE: this is not a full list. You can find all traits in this database):

Herbicide tolerance

• EPSP synthase. A wonderfully short abbreviation for the painfully long "5-enolpyruvylshikimate-3-phosphate (EPSP) synthase". EPSP synthase is a protein that naturally exists in bacteria, plants, and fungi. The protein is part of a system that makes several crucial amino acids in these organisms. The active ingredient in weed killers such as Round-Up is "glyphosate", a synthetic compound that blocks EPSP synthase. The plant can't make the amino acids that it needs to survive so it dies. In order to make plants resistant to glyphosate, the EPSP synthase enzyme from a bacteria was added to the plants. This bacterial enzyme does the same thing (ie. it synthesizes the amino acids) but it's just different enough that glyphosate doesn't block it.
  
  It's important to note that EPSP synthase doesn't exist in mammals, which is why glyphosate has low toxicity. My previous post on glyphosate is here.
  
  In the US, the transgenic crops cultivated with the EPSP synthase gene are: alfalfa, canola, cotton, corn, soy, and sugar beet.


• AAD Enzyme. Another mercifully short abbreviation for "aryloxyalkanoate dioxygenase enzyme" and is from the bacterial species Sphingobium herbicidovorans. The protein breaks down 2,4-dichlorophenoxyacetic acid (2,4-D), a pesticide that's been used for many decades because it kills broadleaf weeds. 2,4-D mimics a natural plant hormone in these weeds, causing their leaves to grow uncontrollably, wither, and the plant eventually dies. The AAD-1 protein allows the plant to break down 2,4-D, so nothing happens to it (for a diagram of the biochemical reaction, please see here).
  
  In the US, there's only one transgenic crop with the AAD-1 gene approved for cultivation: corn made by Dow Agro was just granted approval this year. However, there are several others in the works. 

Insect resistance

It seems odd that no one is demanding for labeling of GM cotton
Image from Wikimedia commons

• Bt trait/Cry protein. There are several proteins from the bacteria Bacillus thuringiensis (Bt) that have been used in various crops and they're known as Cry proteins. Apparently, there are over 200 different Cry proteins from the Bt bacteria and they're toxic to specific orders of insects and nematodes. The insects that Cry proteins target are not all the same, which is why different proteins are used. Additionally, since the protein is toxic to insects, you may also see it referred to as "Bt-toxin". This website from UCSD offers a really simple explanation on how the Bt-toxin works: the protein dissolves in the high pH environment in the insect's gut. Then, it binds to receptors in the bug's gut causing the wall in gut to dissolve, which eventually kills the insect.
  
  Cry proteins are also used in organic farming (if you weren't aware that organic food production uses pesticides, please see bullet #2 here). The pesticide is considered to be benign to humans because the protein's mechanism of action doesn't work on mammals: our guts have a low pH and we don't have the receptors that the Cry protein binds to.
  
  Bt-corn and Bt-cotton have been commercialized. There's exciting work being done with Bt-eggplant in Bangladesh.

Disease Resistance

We had a papaya tree in our backyard in Venezuela.
I love the stuff, but the spouse can't even stand the smell.
Image from Wikimedia Commons. 

• Proteins from plant virus coats. In the United States, there are two commercial crops that have disease resistant traits: summer squash and papaya. Hawaii's Rainbow papaya is one of the great success stories of transgenesis: the papaya ringspot virus was threatening to wipe out this crop, which is a $17 million industry for Hawaiian farmers. In 1997, farmers started planting Rainbow papayas which have a protein from the virus itself. Likewise, transgenic summer squash carries proteins from several viruses which can harm this crop. I previously read up and shared my learning about how these proteins confer disease resistance to transgenic crops. Briefly, the transgene encodes for a protein from the virus (coat-protein) and this "blocks" the infection process from starting (interferes with the virus' disassembly). This is known as "coat-protein mediated resistance" or CP-MR. 

As you can see, there are no blue-strawberries or fish-tomatoes in the list. Such crops have never even made it far enough to start the regulatory approval process. I had written a conclusion for this article, with something along the lines of "See?? There's nothing scary about transgenesis! All you're doing is taking a protein that we know a lot about and moving it into a plant." But then I realized that to a lot of people, that can be scary, so I think I need to explain just a tad further.

You may have read arguments from GMO advocates stating that "we've been genetically modifying food for thousands of years. There's nothing different here." To a large extent, that's true. When you cross breed two compatible species, it's generally because there are specific qualities from species A and species B that you want to blend into a single species. For example, you may want to cross a rice strain that is naturally insect resistant with a second strain that grows very quickly. When you perform such a cross, you're blending all the genes from the two rice strains and then trying to find the hybrid that has all the traits that you're looking for.

Now, imagine instead that you know EXACTLY what gene/protein(s) caused the insect resistance in the first rice strain. Instead of crossing the two strains and blending together thousands of proteins, you specifically add this one protein to the second strain. How would you feel about that? My guess is that the vast majority of individuals would be OK with it. Now how would you feel if that gene/protein came from barley and you're adding it to rice? Again, I think many would be fine with it.

But what if it came from a bacteria?

I think that THIS is where the fear creeps in: the addition of a gene from a species that "doesn't belong". To be clear, I have no evidence to suggest this and have never polled anyone on this topic: it's just from conversations that I've had. And I think the reason why the majority of scientists don't have this fear is because we see things as proteins, and genes, and units, and no gene "belongs" to a species. We see genes/proteins as building blocks that came into existence in viruses and bacteria, and have changed, morphed, been copied, and erased throughout evolution. I work with enzymes (proteins) that have been mutated and morphed by companies so that they do what scientists need them to do in the lab. Back in grad-school, we added and removed genes in mice to figure out what they did in human disease. It was so common, that it had it's own term: "making a mouse". So the concept of adding a gene that we know a lot about into another species doesn't scare me nearly as much as it freaks out the spouse. In reviewing this piece, he agreed with my assessment adding that he views a species as a whole, whereas I view a species as bits and pieces that make a whole.

Feel free to comment below!