The fungi that live in sugarcane manipulate the host plants and the insects that help them spread. Thus, mushrooms play a key role in a complex network of parasite, plant and insect interactions. Never before has it been shown that mushrooms can play such a major role. Brazilian scientists to write About it in ISME Magazine (June 14).
Most fungi are opportunistic: they strike wherever possible, but they do not control their success. Many plant fungi, for example, depend on plant-eating insects and thus provide the fungi with access to plant tissues. But there are also fungi that manipulate their environment. Disreputable Example They are tropical fungi that control the behavior of insects: they affect the central nervous system of those insects causing them to act like “zombies” in favor of the fungi. For example, they gnaw on certain parts of the plant, after which the fungus can break through, or climb to a high point, where the spores of the fungus can better break through to a new place.
The Brazilian study adds a few new layers of complexity
The Brazilian study adds a few new layers of complexity to this. mushroom Fusarium verticillioides It lives in a sugar cane stalk. For a long time it was thought to be an opportunist: it relies on the larvae and adults of the sugar cane borer Diatraea saccharalisSmall moth. These caterpillars damage the cane, allowing the fungus to invade it. The larvae themselves infect the fungus, which helps spread it once they hatch and lay eggs on other sugarcane stalks. New butterflies, eggs, and caterpillars also carry the fungi with them.
The Brazilians discovered that the role of mushrooms is not just a negative one. The fungi have been found to produce volatile compounds that attract both larvae and mites. They demonstrated this in experiments in which insects were allowed to choose between trays of culture medium with or without mold in them.
The researchers conducted these experiments in planting trays and not sugarcane, because sugarcane itself also produces volatiles. They wanted to rule out the possibility that insects would be attracted to substances secreted by an infested plant. It turns out that mushrooms actually produce the same conscious attractants.
However, the affected plants themselves also released a variable spectrum of volatile compounds. This emerged from a second experiment, in which something else also emerged: Infected plants mainly attract uninfected butterflies and caterpillars – and vice versa. The overall picture ensures maximum spread of the fungus, according to the researchers.
“This is a very nice study that shows that mushrooms can modify both the host plant and the behavior of the insect,” answers Paulina Garbieva of the Netherlands Institute of Ecology (NIOO-KNAW). She did not participate in this research, but also wrote herself newly at nature On the role of volatiles in interactions between living organisms. I found this role to be the most interesting aspect of Brazilian research.
“Volatile compounds are unique compounds that operate over long distances,” says Garbeva. “Compared to non-volatile substances, which often accumulate locally, they can easily disperse in gas and water. Our research has shown that they can have a powerful effect on plants and their enemies. Perhaps we can use this knowledge to make agricultural crops healthier.”
This potential application may also be present in the sugarcane story. If you know the function of signaling materials and can mimic them, you can, for example, use them to deter moths. Or go further. The Brazilians have discovered that infected plants are less attractive to the sugarcane borer’s natural enemy: a parasitic wasp (Cotesia flavips) that lay their eggs in moth larvae. The infected plant stops producing substances that attract parasitic wasps.
In fact, this is another achievement of manipulation by fungi. The farmer can take on this lure function by spraying the right volatiles: a new generation of biological control.