Culture of resistance: could friendly fungi offer a helping hand to beans and cassava?

2 November, 2012 by (comments)

Friendly fungi could be the new secret weapon for boosting the resilience of beans and cassava to pest attacks.

Scientists at CIAT and the US Department of Agriculture hope to fight the seed-drilling bean weevil and dreaded, sap-sucking cassava mealybug by introducing a particular strain of fungus to live inside the crops.

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Fungi have long been used in organic pest control. Some do a great job of killing bugs, quickly infecting and colonising them while leaving plants unharmed. Commercially-available fungal “bio-pesticides” are diluted and sprayed directly onto crops or the ground around them, but the problem is you need to apply litres and litres of it to safeguard a whole field. This makes it prohibitively expensive for smallholder farmers, and many don’t have access to the large amounts of water required to dilute it either.

The CIAT/USDA scientists hope to prove that the commercially-available Beauveria bassiana fungus can be transferred into bean and cassava crops. Instead of directly killing the pests, they hope to show that it will help boost the plants’ natural defences against them.

For beans, they will spray the fungus onto the flowers of mother plants to see if it is passed on to the seeds. If successful, it could provide the progeny with some level of built-in pest resistance. For cassava, which is propagated through the planting of stem cuttings from mother plants, they will spray the cuttings.

Both the flower heads and “wounds” on the stem cuttings may offer useful doorways for introducing the fungus into the plants.

You can think of it as a kind of fungal vaccination; a benevolent dose of friendly fungi.

“It’s a similar idea to probiotic yoghurt – but for plants,” explains CIAT entomologist Soroush Parsa, the project’s principal investigator, and himself quite a fun-guy. “It’s all about learning to manage the microbial community inside plants, to protect their health and boost their natural defences. We just need to find a natural method of getting the fungi into the plants.

“If it works it would signify a major leap forward in the biological control of pests: by spraying the flowers or the stem cuttings just once, rather than whole fields several times, farmers need only use a fraction of the amount of fungus in order to achieve field-wide resistance. That also makes it much cheaper and potentially much more effective.”

The project will be funded by a Grand Challenges Explorations (GCE) grant from the Bill & Melinda Gates Foundation. GCE funds research into innovative approaches to some of the world’s toughest and persistent global health and development challenges by investing in the early stages of bold ideas that have real potential to solve the problems people in the developing world face every day. The project is one of over 80 GCE Round 9 grants announced today by the Foundation.

Parsa, working closely with biological control specialist Fernando E. Vega of the USDA, hopes to prove the concept by the end of 2013.

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