Organic Broadcaster

Research moves forward on organic corn that won’t cross with transgenic varieties

By Frank Kutka

These are the parents for the new Liberty (Cycle 0) population for the South. New organic-ready seed is on the horizon.

Photo submitted

Maize, commonly called corn, is an incredibly productive crop that works well in organic crop rotations in many parts of North America. Since the lax release of transgenic varieties of maize (corn carrying DNA from other species) 20-plus years ago, it has become very difficult to grow uncontaminated organic maize.

Why is this so hard? Maize is an outcrossing species of grass that releases millions of pollen grains from its male flowers to blow on the wind and land on the hundreds of silks of the female flowers or ears. Because transgenic varieties have become very common, it is now difficult to avoid transgenic pollen and the resulting contaminated grains.

Organic farmers are not required to produce transgene-free crops, but they must plant seed that is free of transgenes. However, some buyers may choose to reject maize grain that is contaminated. So some organic farmers and processors now test seed and crops for transgenic contamination. Some farmers also plant their corn late in order to miss the plume of transgenic pollen that blows by in midsummer. The results are increased costs and reduced yields. This is reducing our ability to keep organic maize as a sustainable and profitable option.

However, there is another and possibly better way for keeping organic maize free of transgene contamination. There are naturally occurring traits in maize and its weedy relative teosinte that will greatly reduce outcrossing with plants that don’t carry the same trait, sometimes by as much as 99 percent. These traits are called “gametophytic cross incompatibility” because they interfere with fertilization by incompatible pollen—they reduce outcrossing in this otherwise outcrossing species.

These traits were first noticed nearly a century ago among lines of popcorn that would set little or no seed if pollinated by field corn pollen. This incompatibility is controlled by a single allele, Ga1s, while most dent corn only carries the allele ga and cannot readily fertilize Ga1s popcorn lines. The trait is widely used in modern popcorn production to allow planting relatively closely to dent corn fields with much reduced risk of cross contamination.

The popcorn that breeders backcrossed the Ga1s allele into decades ago has been backcrossed into some lines of white field corn in Missouri in the 1970s, and the trait was naturally present in some tropical maize so ended up in some white and yellow field corn lines from North Carolina in the 1980s and 1990s.

Wouldn’t it be wonderful to use this trait for organic maize in general? Well yes, but first a little reality. Although Ga1s, and similar traits like Tcb1s and Ga2s, are powerful natural tools, these genes are not a guarantee of long-term genetic purity. Populations with these traits will need to be checked for unwanted outcrossing from time to time and normal measures to reduce outcrossing (distance, pollen timing, border rows) must still be put into place to receive the full benefit. We would also certainly want to avoid growing organic field corn with cross incompatibility near fields of popcorn that carry the same trait.

Of special note is a concern to reduce the number of volunteer corn plants in adjacent transgenic fields. Such plants could produce some pollen that carried an incompatibility gene from an organic field in the previous year and a transgene from the conventional field, and these could contaminate plants in nearby organic cornfields.

Organic Research
My work to backcross Ga1s and Ga2s has carried on for several years here in North Dakota and far and wide with support from the Organic Farming Research Foundation and assistance from university breeders in New York, North Carolina, Ohio, and Puerto Rico, plus from winter nursery companies in Florida and Chile. I have specifically worked to develop modern populations and inbred lines of field corn with these traits for the development of new inbreds and organic hybrid seed production by organic farmers and seed companies. I also have worked to improve some open-pollinated populations and to backcross these traits into them for the same purpose—organic maize seed that can be more easily saved and sold without transgene contamination problems. Work will continue for years to come as the seed is shared out with other breeders and seed producers here and around the world.

This work began with white dent corn lines carrying Ga1s from Marcus Zuber in Missouri (Mo501w, Mo506w, Mo508w; www.ars-grin.gov), both white and yellow Ga1s carriers from the Maize Genetic Stocks Center in Illinois (401D, 401E; www.maizegdb.org), several white and yellow Ga1s carriers from Major Goodman’s program at NCSU, and the Ga2s yellow dent lines released by Jerry Kermicle to the Maize Genetic Stocks Center (511L, 511M). These have been crossed to populations and inbreds from Seed We Need, Iowa State University and the National Plant Introduction Station in order to generate new populations and lines for public distribution and use.

Research Progress
Inbreds and populations for further breeding and for direct use were developed over several years. Inbreds are self-pollinated to increase the number of fixed genes; they are used to generate hybrid seed. Populations are used for the development of new inbreds and can be used as their own open-pollinated varieties in some cases. Breeders form composite populations by crossing together several traditional varieties and form synthetic populations by crossing together several inbred lines. None of this work involves genetic engineering, just normal sexual means of reproduction.

Painted Mountain (Composite OP): The first crosses of Dave Christensen’s Painted Mountain with Ga1s lines took place in 2003. There will be a multicolored flint/flour population for the North available after 2016. It will be released as Independence (Cycle 0) when it is ready.

Eight Row Flint (Synthetic OP): These populations began in the late 1990s as inbred lines from a number of classic New England Flint varieties and other eight row flint corn. The most recent version of this Ga2s population will be crossed onto the new version of “Pete Seeger” and released in 2017 or 2018 depending on weather. This will be a multicolored flint population for the North, and will be released as Defiance (Cycle 0).

Early Riser (Synthetic OP), Falconer (Synthetic OP), and Red River (Synthetic OP): These dent corn types were crossed with Ga2s carriers and backcrossed for several seasons. They were merged to speed progress after the drought disaster of 2015. The seed will be grown out in 2016 in Vermont and selected for maturity, productivity, and good standing ability. This new mixed population is yellow dent and will be released as Uprising (Cycle 0).

Dairyland (Composite OP): The parents of this silage population were a stiff stalk population from Ontario, a silage corn from Wisconsin, a silage corn from Minnesota, and northern flints with high digestibility. It is aimed at the Great Lakes region. This project will take another two to three years at least. When finished it will be released as Insurgent (Cycle 0).

Hayes Yellow Dent (Synthetic OP): Work on this synthetic population began in 2003 and its normal version was released to Albert Lea Seed House. Its parents were older inbreds that formed strong hybrids and its adaptation is the northern part of the Corn Belt. Seed of the final population with Ga1s, named Revolt (Cycle 0), was released to Sand Hill Preservation Center and to Green Haven Open Pollinated Seed Group in 2015.

Henry Wallace (Synthetic OP): This synthetic population began as some preliminary crosses among commercial and university corn belt dent inbred lines in 2003. This was crossed with the Ga1s carriers from Missouri as part of this project. The population has been released to Green Haven Open Pollinated Seed Group and to Sand Hill Preservation Center as Rebellion (Cycle 0) in 2015, and seed was sent to a cooperative corn breeding project among organic farmers and the University of Illinois in February 2016. It is likely adapted to the central Corn Belt.

1776 (Synthetic OP): Formation of the original eight-line synthetic, based on lines from Iowa and Pennsylvania, began in New York in 2003. An Amish farming group has grown it and passed it around since 2012, and it is carried by Sand Hill Preservation Center. It will likely be adapted to the central Corn Belt. Several more years will be needed to finish backcrossing to Ga2s and the final version will be released as 1776! (Cycle 0) when it is ready.

Major Goodman (Synthetic OP): As part of this project North Carolina lines carrying Ga1s were intermated and then crossed with other lines with southern adaptation (Argentina, Mexico, North Carolina, Tennessee). The final version, called Liberty (Cycle 0), is a white semi-dent for the food grade market in the South. It is being increased in South Carolina in 2016 for public release in 2017.

Zdrowie (Composite OP): The original parents are populations from Uruguay, Argentina, and Chile with stunning, orange seeds. Zdrowie (ZDROH-vyeh) is Polish for health, and these seem to have higher levels of carotenoids. Two or three more backcrosses are necessary for public release of a finished population for the central Corn Belt. Seeds of the normal population are being increased in 2016 and seeds of the “organic ready” version will be made public via the USDA and commercial increase in several years.

Inbreds and populations for further inbred development: Complete conversion of these diverse yellow inbreds was only achieved for a few due to the realities of nursery work. These lines with Ga2s, in varying stages of development, are now available for breeders and will be sent to the USDA for broader public release – Euro Flint, PHK05, RS710, PHM81, LH160, LH149, 73-118, 32-311 C-A, PHJ89, W552, LH54, MBST, NK778, NK794, Q381, LH205, LH128, 73-157, and NYA665ECB/GEMS001.

Conversion of B116 and B119 has also begun but can only progress with approval from Iowa State University. Also, I am releasing yellow dent Ga1s-carrying populations for the 90-100 day maturity zone that are by pedigree 50 percent B14, 50 percent B73, 50 percent Iodent, or 50 percent Mo17. These should greatly speed up further breeding with these traits by our organic hybrid seed companies, or could be used for nontraditional types of hybrids by anyone far sooner.

Frank Kutka is an independent plant breeder who collaborates with Dave Christensen on the “Seed We Need Project.” He also co-coordinates the Farm Breeding Club, a project of the Northern Plains Sustainable Agriculture Society.

From the July | August 2016 Issue

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