Earlier this week CBS News reported on a herd of roping cattle near Austin, Texas that had been gassed - to death for 15 of 18 members of the herd - by hydrogen cyanide [HCN], by the grass in their pasture. Fields nearby were quickly tested and found to also be outgassing HCN but not in lethal amounts. The fields were all planted in a hybrid bermudagrass cultivar known as Tifton 85.
The cultivar was originally identified as a GMO, which turned out to be erroneous if one limits the designation to cultivars produced with recombinant DNA technology or "gene-splicing." The press duly corrected the error, though that didn't diminish the suddenly spurred public interest in an aspect of American agriculture that had until now been obscure to unknown to average people.
So I thought I'd take the opportunity provided by current interest to explain a bit about what happened. Of course, my own curiosity got the better of me when the story broke, so readers can blame that if this all turns out to be more than anybody who isn't in agriculture ever cared to know. The interested and semi-interested may venture below the Orange Squiggle of Power for the straight dope, if they dare...
As it turns out, the anti-GMO organics crowd weren't the only ones who reacted viscerally to the original report that this grass is a GMO cultivar. Pro-GMO forces weighed in early and loudly, as did their fans and followers. One of the first websites that showed up in my many searches while trying to track this down was Agriculture Proud, a cattle rancher's blog. About the subject of Tifton 85 and under the heading of 'Tifton 85 is a Hybrid, Not a GMO', the blogger wrote:
Tifton 85 is a cross between a bermudagrass [Cynodon dactylon, specifically cv. Tift 292 (an armyworm resistant plant introduction in the USDA-ARS collection)] and a closely related Cynodon species called stargrass [Cynodon nlemfuensis, specifically cv. Tifton 68 (highly digestible, but cold susceptible). Crosses were made by placing inflorescences (the day before pollen shed) of each parent in a beaker of water. The inflorescences were covered with a glassine bag to control pollination. Each day, thereafter, bag and inflorescences were thumped to distribute pollen. Seeds were collected and those were germinated in the greenhouse and subsequently transplanted in the field. Plants with great potential were increased and selected to be tested in replicated plots and under grazing. No extraordinary tools or biotechnology tools were used in this process.
Obviously this guy did some homework, but
he got it wrong too. I guess this stuff is obscure enough that even otherwise knowledgeable people don't know much about it. Deal is, Tifton 85, like many varieties of turf grass, propagated clonally by means of cuttings and tissue cultures in petri dishes. That's because it's sexually sterile - does NOT produce viable pollen or seeds. Instead, it propagates in the wild by means of rhizome runners that establish new colonial clumps.
These clumps are grown into sod at sod farms, and from the sod 'plugs' are produced. The pasture is then planted with the plugs and those eventually grow together into a nice even turf. Bermudagrasses and hybrid cultivars of that variety are not only popular, high protein pasture grasses for livestock grazing and hay, they cover the fairways and greens of golf courses all over the country/world as well.
Now, I've driven myself dizzy over the last three days reading scholarly treatises about breeding clonal cultivars, even put in an urgent request to my sister the plant physiologist [retired]. I've found out lots of things, but NOT how the heck they manage to mix genes/chromosomes in the tissue cultures they establish for the purpose. I mean, they didn't use recombinant DNA tech, or Tifton 85 would be a certifiable GMO. For all I know they might have inserted chromosomes from one cultivar into cells of the other, but that doesn't seem very efficient and I can't find any indication that's how it's done. The two cultivars for Tifton 85 are C. dactylon - which is fairly cold hardy and armyworm resistant - and a closely related African stargrass. The cultivars have different numbers of chromosomes, so if anyone here does know how this is done in vitro, I'd be glad to learn!
Meanwhile, I have learned that specialized varieties of bermudagrass have been produced in a number of unnatural ways that generate mutations that can then be artificially selected if they show useful traits. Gamma radiation and particle bombardment among those ways, which sort of conjures up fantasies of little clumps of grass at the target end of linear accelerators and cobalt X-ray machines and such. Sometimes they use bacteria or viruses to generate mutations. And then some researcher or other at a land grant university or crop corp is going to cross those artificially mutated cultivars in vitro with other artificially mutated cultivars to produce hybrids and hybrids of hybrids…
The Tifton 85 in this Texas pasture had been there for 15 years and the cattle had been doing just fine on it. 'Official' suspicions about why it suddenly turned into a gas chamber have to do with a common stress response in plants, especially after heavy nitrogen fertilization, which the rancher apparently did when prepping the field for his cattle. Stressed and/or ruptured cells mix their enzyme content with dhurrin to produce prussic acid (hydrocyanic acid). Stress in this case is likely to be pinned on long term drought. The prussic acid in this grass must surely have been high enough to have poisoned the cattle just from what they ate, though it seems the gas got them first. See: Texas AgriLIFE Research, Stephenville: Prussic Acid Poisoning.
Most people don't realize that livestock poisoning by prussic acid in fodder is fairly common. Losses are from 3% to 10% annually. 3% from cyanide, 10% from all poisonous plants. This sensational Texas case demonstrates that even this kind of hybrid can destabilize without warning years down the line to become fatally toxic. Though I don't think there's anything Big Ag could (or would) do to prevent it. Shit happens.
Yes, there are all kinds of natural plants that produce prussic acid in their tissues - notably prunus species like cherry, apple, apricot, etc., but also grasses and other herbal vegetation. These have been known to kill livestock through ingestion, a perennial problem. Under stressful conditions they can and do release cyanide gas to the air as well, though in sufficient amounts to kill off herds of grazers is unprecedented. It would appear that there is an issue with the polyploid genome of the Tifton 85 cultivar producing more HCN under extended stress than other natural and hybrid cultivars do. So we can hope that the hybrid cultivars of bermudagrass that carpet golf courses all over the country don't begin to suddenly drop members of the PGA (and their caddies, and their fans) during golf tournaments. Still, this is something that needs to be thoroughly investigated and quantified for potential problems just in case. Thankfully the USDA is now investigating.
Finally, for all who were so rude about people's concerns when the story broke and the news was that this was a GMO, lighten up. It is a GMO, just not the same kind of GMO as RoundupReady or Bt cultivars. It wasn't produced via recombinant DNA/gene insertion w/viral attachments technology, but it WAS produced by humans on purpose and artificially selected for specific traits and is not something that would likely have arisen naturally.
More Informational Links:
Bermudagrass Tissue Culture and Genetic Transformation through Agrobacterium and Particle Bombardment Methods
Developments in Warm-Season Turfgrass Breeding/Genetics
Examiner: 15-Year Old Field of Grass Suddenly Produces Cyanide
Cornell: Breeding and Genetics of Forage Crops
UGa: Alternative Strategies for Clonal Plant Reproduction
Microsatellite Molecular Markers Accurately Identify Clonal Turf Bermudagrass Cultivars
Polyploidy & Hybridization in San Diego County
Tifton 85 Bermudagrass
Texas AgriLIFE Research, Stephenville: Prussic Acid Poisoning
CDC: Facts About Cyanide
Wikipedia - Hydrogen cyanide