Green Revolution 2.0? Using molecular markers to speed up Mendel


In agricultural technology circles, when talk turns to plant breeding as a way to boost crop yields, combat plant diseases, and adapt to a hotter, drier world, genetic modification has frequently dominated the conversation. This includes the Roundup-ready suite of crops, resistant to herbicides, or BT corn and soy, which are modified to manufacture their own pest toxins.

Yet as a recent article by science writer Richard Conniff in the online environmental magazine Yale E360 points out, advances in molecular technology have done more than make the world a better place for Frankenfoods. They've improved traditional plant breeding. Using molecular marker techniques, breeders are now quickly developing plant varieties with beneficial characteristics like drought tolerance or increased vitamin concentrations.

This technique, called marker-assisted selection, is allowing the old school plant breeders, who create new strains of plants in a way similar to that of Gregor Mendel or your average 19th century farmer -- by crossing two plants that each have desirable characteristics -- to speed up their work. As marker-assisted selection becomes more popular, it could improve agriculture in a wide range of locations, including the West, where plants could be developed to grow in compromised soils, hotter climates or low water conditions -- without the negatives associated with current genetically modified crops, which can range from bee deaths to organic crop contamination to widespread herbicide use that creates resistant Superweeds.

This method was first proposed as an option by scientists in the late 1980s. At that time, though, the genetic sequencing necessary to undertake this type of breeding was cost prohibitive. Now, sequencing a genome is relatively cheap -- in the thousands of dollars.

Here's how it works, writes Conniff:

(R)esearchers sort out which genes are responsible for a given function, the bottleneck in the process so far, though (it's becoming) faster and cheaper with each new species that gets sequenced, because nature tends to employ the same mechanisms from one species to another. Finally, researchers map out markers -- bits of genetic material that are linked to those genes, to flag whether or not the desired genes are present in a given individual.

Coniff then goes on to explain how the process works with tomatoes. Traditionally, breeders would have to wait until each new tomato cross grew to maturity, and then test to see if it had the desired traits. Then, they'd repeat the process, breeding the plants again to see if those traits were maintained.

Breeders now use genetic markers to automatically screen one-inch-tall seedlings and immediately weed out the 99 percent they don’t want, cutting years off the breeding timetable. That makes it easier to get to (the) desirable cross-breed quickly -- and also stack up a complex array of traits in a single strain.

In January, scientists at New Mexico State University announced they had used this technique to develop a variety of drought tolerant alfalfa. Alfalfa farmers and beef and dairy producers in Texas and New Mexico probably wish the finding had come a few years earlier, but if this variety becomes widely used, it could help prevent the widespread economic disruption from reduced hay supplies that came during the recent drought.

A Kenyan scientist prepares maize samples for DNA analysis to use in marker-assisted breeding. Image courtesy CIMMYT

Scientists at UC Davis have also used this technique to develop a more nutritious wheat.  And early this month, University of Idaho plant breeder Jianli Chen, who also uses marker assisted selection, announced she hopes to release a disease-resistant, drought tolerant wheat variety for commercial use in Idaho by 2013. A development like this could be good news for many farmers in the northern Rockies and Great Plains, where wheat is a major crop.

And let's not forget the salmon. Yup. You read correctly.  A new type of farmed Atlantic salmon has the potential to wipe away the major negatives associated with traditionally-farmed salmon, which pollute the ocean, can escape and potentially compete with wild salmon for resources, and can also transmit disease and parasites to wild salmon who come in contact with them.

A company called AquaSeed has used marker-assisted selection to breed Atlantic salmon that grow fast enough to be economical in land-based tanks, which are more environmentally friendly than the conventional, ocean-based cages. These salmon are also more nutritious, and are the only farmed fish to appear on the watchdog group Seafood Watch's Super Green List, meaning they are both environmentally benign and good for human health.

It looks like, now that costs have come down, traditional breeders are succeeding in doing what GM plant developers have long promised they would eventually do: Use molecular technology to develop crops that work in extreme environmental conditions, add nutrition or disease resistance, or generally improve agriculture for the public good. So rather than spraying more Roundup, we may be ending up with tastier and more nutritious tomatoes, hay that can grow with less water, and wheat that withstands the crop-killing diseases that can devastate farmers in wide swaths of the West.

Stephanie Paige Ogburn is the online editor at High Country News.

DNA sculpture image courtesy Flickr user ἀλέξ