Simply fussy plants

July 2016

Oilseed rape: photo Creative Commons

"Genetically modified organism means an organism's DNA was changed to make it different, often to make it ... contain more usable parts."

One old-timer plant biologist recalls "heady times" when he walked up and down rows of flourishing GM oilseed rape growing side-by-side with its "struggling" conventional counterpart in an experimental low-nutrient soil.

This GM rape had an extra artificial gene, copied from barley, which helped it use nitrogen more efficiently. It promised to be the answer to the world's increasingly degraded and depleted soils.

The 'barley' gene itself doesn't seem too controversial, and has been successfully inserted into wheat and rice, both major staple food crops. Nevertheless, while Big Biotech has been developing fertilizer-frugal GM crops for over a decade, it admits these are still at the 'proof-of-concept' stage and nowhere near the market.

Water-efficient GM crops haven't so far fared much better: DroughtGard maize was the first such marketing attempt, but suffers from patchy yields.

Elsewhere however, scientists focusing on the whole plant rather than isolated genes have had considerable success. Nutrient- and water-efficient plants have been developed with increased yields of between 20 and 144 present.

The International Maize and Wheat Improvement Centre (CIMMYT) in Mexico has won regulatory approval for 14 nitrogen-efficient maize varieties across six countries, and has more than 50 other new maize strains in the pipeline, all produced by conventional breeding.

A team in Pennsylvania State University has been researching something much more obvious, but messy. Since nutrients and water enter through the plant roots, the team has been painstakingly unravelling and examining roots to relate structure to function.

Root structure is complex, involving, for example, every combination of longer, shorter, more/less branched, more/less lateral, and hairiness, all of which impact on where and how the roots interact with the soil structure, nutrients and water.

The knowledge of which root structure can better access water in drought conditions and better source nutrients in impoverished soils has led, for example, to the development of conventionally bred bean crops with up to three-fold yield improvement. Beans are an important food crop in Africa.

OUR COMMENT

The scientist once so impressed by GM oilseed rape is now disillusioned. GM clearly isn't delivering.

He notes that GM crops are unpredictably fussy: they do well in one environment, but not in others. This doesn't make for a marketable product.

Putting the problem another way, extrapolating a gene from barley physiology into oilseed rape physiology, and expecting the novel plants to cope with both the internal stresses imposed by the novel gene plus the external stresses imposed by the environment is a very tall order indeed.

In the wonderfully simple definition of GM given above, the key words are "make it different".

Natural genes assembled during natural breeding, talk to each other: adjusting themselves to accommodate the current needs of the whole plant and its surroundings comes naturally to them. Artificial genes may be "usable parts" in terms of producing a novel protein, but they speak another language, an artificial language, that natural genes won't ever learn.

SOURCES

• Christopher Stephens, Red Gold ousts most GMOs, liner chemical, Herald Bulletin 1.05.16
• Natasha Gilbert, Frugal Farming, Nature 533, 19.05.16
• Monsanto's "DroughtGard" Corn Barely a Drop in the Bucket, Union of Concerned Scientists, 5.06.12
• Mike Minford, Farmers test drought-tolerant corn hybrids, Corn and Soybean Digest, 23.01.15