Return to Resistance: Breeding Crops to Reduce Pesticide Dependence

Return to Resistance Coverreview by Liz Henderson

This book has been available for over 20 years, but the theme relates perfectly to the theme of this special issue of TNF, connecting the method of plant breeding that has dominated in the US with the need for the excessive and increasing use of pesticides. Robinson, who passed away in 2014, according to Wikipedia, was “a Canadian/British plant scientist with more than forty years of wide-ranging global experience in crop improvement for both commercial and subsistence agriculture.” He was a practitioner and a champion of horizontal or population breeding, an approach that attempts to replicate the level of resistance to pests and diseases found in uncultivated crops and resembles the way farmers have selected crops for millennia.

According to Robinson, it was J.E. Vanderplanck in Plant Diseases, Epidemics and Control, who distinguished between single gene and multi-gene resistances.  He called single gene resistances “vertical:” they are qualitative – the resistance is either present or absent with no gradations. By contrast, “horizontal” resistance is quantitative and can occur at any level from a little to a lot.  Pedigree breeding, the approach favored by the Mendelian school (followers of Mendel, whose “laws of inheritance” we have all studied in basic biology), is based on vertical resistance, a gene for gene relationship between a plant and its parasite.  This form of resistance is also temporary, requiring the breeder to continually develop new cultivars as the resistance inevitably breaks down, or to resort to pesticides and fungicides to ensure high yields.

By contrast, horizontal resistance is complex and durable, involving many polygenes “controlling many different resistance mechanisms.” (p. 402) Robinson gives many examples of crops that farmers were able to grow for hundreds of years without resorting to pesticides – sugarcane, ancient clones like garlic and ginger, olive trees, bananas, hops, etc. Breeding plants for this kind of resistance does not require that there be a genetic source of resistance which is what the Mendelian breeders need to even begin.

Return to Resistance is a passionate argument for increasing the resources dedicated to horizontal breeding.  Robinson insists that he admires the accomplishment of the Mendelians who have had great success with three of the broad objectives of breeding – “to improve the yield, the quality of crop product, the agronomic suitability…” (p. xiv)  However, he blames the steadily increasing use of toxic pesticides on their failure with the fourth objective: “the resistance to pests and diseases…”

Section one of his book gives a clear explanation of the differences between the two approaches to breeding and the way pests and diseases behave.  Section two give examples of successful horizontal breeding, including his own experience saving the coffee crop of Ethiopia.  There is a fascinating chapter on the history of potatoes, the Irish famine resulting from reliance on only one variety that was devastated when late blight, a new pathogen, arrived from Mexico. Then, as varieties with horizontal resistance were selected to replace the susceptible one, the role of potatoes as a basic crop to feed the poor recuperated.

Section three is entitled “Solutions.” To counter the dominance of the Mendelians, and their offspring, the gmo breeders, Robinson urges the formation of Plant Breeding Clubs.  He believes that only active and organized amateurs together with farmers can defeat the “vested interests,” the major seed companies and pesticide manufacturers who “positively require susceptibility to crop pests and diseases,” to justify their existence. (p. 254) He provides a detailed guide to forming these clubs including a glossary defining all the techniques and materials a club might need along with a warning against wasting energies on crops that are too difficult or require professional training.

In the final chapter, Robinson looks to the future. Optimistically, he predicts the development of a new discipline – “agro-evolution.”  Replacing Mendelian breeding, “it will be based on horizontal resistance, and both pathosystem theory and complexity theory.  The complexity theory will ensure that the screening process takes place at the edge of chaos, and that all factors are allowed to exert their natural influence on the self-organization, the appearance of emergents, and the agro-evolution.” (p. 396) Upon this statement follows Robinson’s lucid analysis of the limits of genetic engineering relying as it does on the transfer of single, or at most, two or three genes. As with vertical resistance, parasites can overcome this simple gene transfer with their capacity for micro-evolution. Robinson predicts the kind of failure we are seeing now with superweeds bedeviling the farmers who are trapped in the tentacles of the Bayer/Monsantos.  He concludes cheerfully “Perhaps plant breeders’ clubs working with horizontal resistance may not be such a bad idea after all.” (p. 403)