HORTICULTURE Leaf infected with Myrtle rust
CONFRONTING
Photos: Brett Summerell and John Siemon, © Royal Botanic Gardens and Domain Trust
A MENACE PLANT BREEDING IS A COMPLEX PROCESS AND SOMETIMES THE STAKES ARE EXCEPTIONALLY HIGH, WITH SCIENTISTS RACING TO STOP PATHOGENS WIPING OUT ENTIRE SPECIES. JOHN SIEMON REPORTS.
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t’s easy to take for granted the importance of genetic diversity. Few shoppers, when purchasing a bunch of bananas, a bag of potatoes or a loaf of sourdough, pause to consider the chain of custodians that have brought the product to their fingertips. Pushed to list those involved, they might mention the farmer, the truck driver or the baker. But would they think about the agronomist, the plant pathologist or the plant breeder, who were equally, if not more important in ensuring the careful selection and cultivation of genetically diverse cereal grains that were resilient to an army of evolving plant pathogens? Many of our decisions involving plants, whether we like it or not, have
been determined for us, and in many cases that process took place years before it touched our lives. In the case of plant breeding, the timber frames that make up modern house construction may have arisen from forestry tree plantation breeding programs 30 years ago. And think about the produce that we buy from supermarkets or fruit shops – its domestication may have started thousands of years ago, with active breeding programs in more recent years improving yield, disease resistance, flavour, vigour or shelf life. In the ornamental horticulture world, many advances in plant breeding have occurred by exploiting natural variation with minimal breeding. Sometimes
exceptional forms of plants arise by chance or because they have an evolutionary advantage. For example, floriferous specimens are more likely to be visited by pollinators and therefore more capable of producing seeds, improving the chances of survival for more individuals in the next generation. Plant breeders with a keen eye can identify attributes most likely to be sexy in a plant pot, and cross pollinate individuals of successive generations until the desired attributes are achieved. Extensive plant breeding over millennia has enabled global human populations to explode, and today feeding an ever-increasing number of mouths with diminishing resources is a
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