I was curious about the corn farm post. How do Botanists find or induce mutations in plants?
well, in the corn post, all those plants were plants that the corn breeders at the facility had found in the field. the facility i work at is interesting in that the plants that grow at the main “home” nursery - where the zoo corn lives- aren’t the corn varieties grown in farmer’s fields, but the parents of the corn varieties grown in farmer’s fields. this is a little sidetracked but ive been wanting to talk about it for a while bc i bugged the breeders about it until they told me: so like, all the varieties at the nursery crossing facility are inbreds. like, they’ve been bred with themselves down up to 13+ generations. this means that when you work in the nursery with the inbreds and then work in fields with commercial corn, you notice some distinct things about the stuff that has been inbred for years:
-the plants are stunted. like, they are physically smaller plants. they’ll go above your head, but not by much (im like 5 foot 5). corn in the field can be regularly be like, 7-8+ feet tall.
right now, we’re doing data collection on our hybrid corn, which involves me and a team of four other people driving out to a test field each day with literal 144 inch tall folding yardsticks and a breeder’s assistant with an ipad or data collection device; our whole job, for the past week and a half (and for the next two weeks), has been to go from row to row in certain columns of the corn and shout out plant and ear heights as we measure the corn in certain areas. from here, the breeders can use the data to calculate an average plant hight and ear hight for each variety in testing (there can be thousands per field). usually, the corn we measure is between 100 inches and 120 inches. a couple days ago we visited a field that’s notorious for drought conditions, and this year was no different- the corn was stunted to about 80-90 inches. the corn in the nursery can be anywhere from 80-100 inches, usually, but stuff that has been inbred for more generations tends to be progressively smaller.
-the plants get mutated in really weird ways. the most common ones we see in the inbreds are things like whip tassels (where the flag leaf on top of the plant concealing and protecting the tassel tightly around it instead of opening it up for pollination, causing the whole top to curl up into a tight semi-circle shape), cases where corn will be growing out the top of the plant (the corn “ears” generally grow off the side of the plant, as the female flowers; the male flowers are the tassels on the top. in this case, the plant has no ears and instead has decided to fuze its ear into its tassel, so you get a weird, mutated tassel with random kernels everywhere and dying tassel strings hanging out), cases where the whole plant is just a mess (leaves dont furl out all the way and are misshapen, tops are mutated, ears dont grow, tassels dont grow, and the whole plant is stunted to knee height), etc.
-the plants don’t germinate. like some varieties just dont germinate after so many inbreeds, for whatever reason; something along the line just got so mutated that the whole seed just decided to stop growth altogether. this is a really weird thing that happens because you’ll be walking through the varieties and suddenly there will be a completely bare section with like, one stunted and mutated plant sitting in the middle. thats all thats left because thats all that germinated
you may be like “why would you inbreed plants so much???” and the idea is to create a pair of purebred parents so you have a better cross. the plants are bred with themselves until they reach 100% genetic homogeny. so every. single. plant. in the variety. is genetically identical. you may be like, “whoa i didn’t know that was possible!!!” and thats because it is, but like. its illegal in humans. its the same genetic ideals, but…it doesn’t apply to humans well. for understandable reasons.
anyway, so, the plants are crossed, and then the hybrid children are badass. they have all their genes recorded. they’ve been planned down to the nucleotide for the market. because their parents have the same genes in both their lines, every single plant is more or less dependable and reliable– you won’t have random secondary traits popping up. hybrids are stronger, more disease resilient, and generally bred specifically for farms– and that’s the corn that gets sent to production facilities. the production facilities grow them en mass and multiply them up, then sell the grain as seed to farmers, who then have hardy, reliable seed for their fields.
so like, the mutations. all that stuff?? its kind of accidental, but when you work with plants that are explicitly cultivated for performance…like, all the stuff that naturally would stop mutations in the wild (for example, there’s not much of a chance that you’re gonna get bred with yourself 13+ times in a row) kind of gets thrown out the window, and weird stuff happens. that being said, bending the rules like that has allowed us to make huge strides in breeding.
that being said…if you wanted to cause some plant mutations, it’s not hard. for example in the book ive been reading since it was recced to me yesterday (”Flower Confidential” by Amy Stewart, which talks about the ornamental cut flower industry) there are some techniques that get used for intentional mutations. like, they were talking about Plant Patent 165, one of the first patented plants (patented in the 1930s) by General Electric. In flower breeding for cut flowers, it’s undesirable to have plants that shed flower everywhere. #165 (a lily variety called “Regal Lily”) was one of the first patented plants ever, and didn’t shed pollen due to a treatment where the seeds were X-Rayed for 30 seconds, causing a sterile mutation. from the same book comes this example:
so mutations: sometimes they’re intentional, sometimes they’re bred into it, sometimes its accidental or caused by overbreeding as a side effect. thats completely excluding GMO manipulation btw
P.S. “corn” in this post means Maize specifically, for those wondering