Food security: developing disease resistant crops and preventing disease spread
The oil palm provides more than one third of the world’s vegetable oil and is a major source of revenue for commercial producers and smallholders in Africa, Brazil and South East Asia. The palm is attacked by two pathogenic fungi that cause major losses in yields and profits.
Devastation caused by soil-borne fungal pathogen Fusarium in an oil palm plantation in Ghana
Researchers led by Dr Richard Cooper in The Department of Biology & Biochemistry have been working closely with oil palm producers to combat fungal crop diseases and protect yields and profits. The resulting knowledge and technology transfer has contributed to increased food security at local and global levels. In this project, the researchers have found that sometimes the simplest ideas can have a huge impact.
They are working to control two fungi:
- Fusarium – a soil-borne fungus, which has devastated the palm oil industry in Africa
- Ganoderma - a bracket-forming fungus that causes extensive yield losses in Malaysia and Indonesia, resultng in estimated losses to one company alone of $66 million
Dr Cooper commented: “In order to control these diseases we need to understand the basics of epidemiology and route of infection. But the bottom line is to develop disease resistant lines and to stop the diseases spreading to new areas.”
Fusarium outbreaks from contaminated seed
Outbreaks of Fusarium in Brazil and Ecuador were caused by Fusarium-contaminated seed imported from Africa, the centre of genetic diversity for oil palm. The researchers have developed a simple technique of treating the seeds with fungicide under a vacuum so that the fungicide is sucked inside the seed, eradictating the pathogen and preventing disease spread to disease-free areas such as Malaysia.
The technique is now used by companies in Congo and Ghana, and also by the quarantine lab in the UK. The scientists also designed and supplied the equipment used for the technique to a company in Ghana in 2011.
Using this technique has allowed seed companies to market their product as certified “Fusarium-free”, which has enabled one company to increase the price of seed by 15%.
Technology transfer from the group’s research has also improved diagnosis of the disease by using core sampling of the palm stem instead of relying on visual symptoms to assess whether the disease is present.
Ganoderma spreads via airborne spores
Oil palm fruit bunches. Palm oil is extracted from the outer fleshy part of the fruit. A separate oil is obtained from the seed (palm kernel oil).
Cracked seeds are shown that have been infiltrated under vacuum with fungicide. A red dye shows penetration to the inner kernel where it is required to eradicate Fusarium.
The group’s latest findings have revealed that Ganoderma spreads mostly via spores in the air - rather than only through the soil, as previously thought.
The research, published in the international journal Plant Pathology, found that isolates of the fungus from adjacent infected palms were genetically different from each other. This indicates they arose from the vast number of sexual spores produced, rather than spreading as a clone through the soil.
Dr Cooper explained: “Harvesting the fruit for oil extraction requires removing the surrounding leaf stalks of the palm and these wounded surfaces become covered in spores which get sucked into the plant through the water conducting channels or xylem."
“Our work suggests that infection could be reduced by protecting the wounds after harvesting and by removing the spore-forming fungal brackets. However Ganoderma also spreads via the soil so the best way to stop spread of the disease is to breed resistant plants.”
Dr Cooper helped improve trials for disease resistant varieties by introducing some simple changes.
He said: “We found that plants in trials that were exposed to full sun were not becoming diseased, whereas those accidentally shaded by nearby trees were. The tropical sun was heating the soil to temperatures above 40ºC and killing the pathogen – simply introducing shading to mimic the conditions under the leaf canopy in a plantation made the trials a lot more effective. Most companies now shade their trials as a result of this work and using artificial shading has shortened the duration to select for disease resistance from 12 to 8 months.”
Dr Cooper is now advising a major company in Malaysia and the Malaysian Palm Oil Board. His group is also developing a new DNA probe that uses fingerprinting techniques to identify Fusarium infections and to detect them in seed shipments.
Dr Cooper said: “This ongoing research involves collaboration with Africa, Brazil and Malaysia and postgraduate students and researchers from there. We still have a long way to go but are making significant inroads and providing regular knowledge and technology transfer”.
The researchers acknowledge Unilever plc, BBSRC, LONSUM, EU, FELDA and the Malaysian Palm Oil Board have all provided funding that contributed to this work.