Evolutionary breeding, just like weeds

September 2022

Despite all the toxins, genetic devices, and shear physical destruction we throw at them, pests of all kinds continue to thrive in our fields. As climate change imposes all manner of unusual stresses on the environment, farmers and their crops struggle, while pests go from strength to strength.

It's not too difficult to see why. 

For one thing, heat speeds up the metabolism of many organisms, especially insects, increasing their food intake and reproductive ability. This means that, with higher average temperatures, heat- and drought-stressed crops are plagued with more active pests.

Add to this that pests have mobility. If the conditions in one area become less suitable, many pests can spread themselves around and set up shop somewhere more hospitable. Crops are confined by their human masters to specific tracts of land, where pre-determined conditions are chemically and physically adjusted for maximum yield, but are not necessarily ideal under extreme weather conditions. When the pests which don't like the current weather move out, new ones which do like it move in.

The greatest advantage pests have over crops is that they can change themselves very, very quickly. They can do this because they're part of a natural population with a natural genome consisting of a large and naturally diversified gene pool which has evolved naturally in whatever environmental conditions they find themselves. Pests have, therefore, the genetic and physiological resources to adapt to new stresses. The agrichemical war on pests which is part and parcel of modern conventional agriculture is just another environmental stress to which pests naturally adapt.

Our staple crops are, typically, super-intensively bred for maximum yield: this means uniform genomes which produce uniform plants treated with uniform chemicals dictated by the agricultural suppliers.

Compare and contrast the 'bottom up', self-regulating and diverse world of pests with the 'top down' commercial control and uniformity of modern 'conventional' agriculture. Put another way, pests adapt themselves to their changing environment: farmers change the environment to adapt it to their crops.

Our fuel-dependent, resource-sapping, globalised system of agriculture makes a significant contribution to climate change. It seems abundantly clear that we urgently need to protect our food supply both by mitigating the environmental catastrophe threatening to engulf us, and by ensuring our crops aren't vulnerable to the extreme conditions they're facing.

While continuing to promote the minimal crop variety, large-scale, chemical-dependent climate-changing agriculture on which their profits depend with one hand, the biotech industry is promising farmers 'climate-smart' GM seed with the other. These novel crops will have traits focused narrowly on key climate-change-related problems, such as a disease, an insect pest, a drought. The reality of several pest challenges, novel pests, heat, cold, drought and flood all presenting together and changing unpredictably from year to year, and from location to location, can't be solved by any such reductionist, one-size-fits-all, silver-bullet approach.

How do we break free from the corporate monopoly of our food supply and the culture of dependency that hybrids, patented GM crops and agrichemicals have created?

Two scientific reviews were published in 2020 describing a range of crop development and breeding strategies which, together, would reduce agricultural greenhouse gas emissions, produce crops able to adapt to climate change, and improve human health.

They suggest a re-diversification of our whole food supply, to include both the in-farm range of crops and varieties grown and their genetics, coupled to on-going local adaptation of the plants using 'evolutionary breeding'. In this scheme, crops with a wide genetic variability are generated by breeding using a range of sources, including heirloom varieties, seed banks, breeding programmes (which may have used marker-assisted gene selection to enrich desirable traits) and farmers. Whereas current commercial crops are bred for maximum yield, the sole criterion for successful evolutionary breeding is resilience.

This diversified and adaptable stock is then subject to on-farm 'evolutionary' breeding where it naturally evolves into a locally optimised sub-variety retaining the resilience needed to buffer it against climate change and pests (without reliance on chemicals).

On the subject of human health, the authors note "... in the last 10 years, medicine has recognized the association of agrobiodiversity with diet diversity and human health. In fact, the composition and diversity of the (gut) microbiota affects both our physical and mental health, and the diet affects the composition and diversity of the microbiota. Nutritionists recommend a diet as diverse as possible for having a healthy microbiota, but a diversified diet remains a challenge, given the decline in agrobiodiversity described ..."

Noting that organic agriculture is not only climate-change friendly but is able to mitigate its effects, the authors are confident of the usefulness of evolutionary breeding in this area too. However, at the moment the potential for organic agriculture to feed the world is largely unexplored due to the limited number of breeding programmes on the subject. Also, organic farmers often struggle to find organically produced seed of suitable varieties.

OUR COMMENT

Using GM golden rice as an example, Stone and Glover describe it as "profoundly disembedded and placeless: an invention of European biologists who used primarily American funding to insert DNA from scattered locations across the biological kingdoms to alter Green Revolution rice in order to treat malnourished children of Asia, partly to help fight a global public relations war". (GM Watch)

Top-down, one-size-fits-all crops? Or, bottom-up locally adapted crops with maximum resilience?

Which of these make most sense, especially in the face of climate-change?

Perhaps we need crops which are more like weeds.


SOURCES:

• Salvatore Ceccarelli and Stefania Grando, December 2020, Evolutionary Plant Breeding as a Response to the Complexity of Climate Change, iScience

• Salvatore Ceccarelli and Stefania Grando, 2020, Organic agriculture and evolutionary populations to merge mitigation and adaptation strategies to fight climate change

• Evolutionary plant breeding allows farming to respond to complexity of climate change, GM Watch 12.01.22

  Photo Wikimedia Commons