Natural insecticide

Plant & zo

The science of plants and more


Natural insecticide

Plants have an arsenal of weapons to deal with insects. Think, releasing for the insect unpalatable smells, or maybe smells that attract predator insects that eat the plant eating ones. But also think, releasing a, for insects, deadly toxin. This all makes sure that a plant will survive a plague of hungry insects.

Unfortunately, most of our cultivated crops have lost this capacity. We have optimised these in such a way that they have large yields, with great taste. Only on the way we have lost their natural protections against insects. These we have used insecticides instead.

Still it would be useful to give crops back their natural protection against insects. This is what scientist are trying to do. But it is not as easy as it sounds. Researches from Brazil and the Netherlands crossed cultivated tomato plants with their wild relatives to try giving back their natural protection.

Tomato plants produce natural insecticides in their trichomes. They are a kind of hairs attached to the leaf and gives them hairy or downy appearance. You have trichomes in all different kinds and sizes. The trichomes that make natural insecticides have a globular ending, in which the insecticide accumulates.

By crossing in type-IV trichomes into cultivated tomato plants, Brazilian researches hoped that these would also make the by type-IV trichome produced acyl-sugars. Unfortunately, this was not completely the case. The plants did make acyl-sugars, but not enough for killing insects. But with the type-IV trichome tomato plants in hand, the Brazilian research are trying to find out how they can make them produce lots of insect killing acyl-sugars.

A team of Brazilian and Dutch researchers tried a different approach. By crossing cultivated tomato plants with their wild relative they selected for genes involved in the production of natural insecticides, this time sesquiterpenes made by type-VI trichomes. Their progeny did make more of some sesquiterpenes, but not all, and did not make more type-VI trichomes. It also turned out that not enough of the insect killing type of sesquiterpenes were made.

So even though researchers did not manage this time to give back cultivated tomato plants their natural insect protection. They did lay the next steppingstone for the way to it. We do know a little better how wild tomato plants make natural insecticides and use them. They do this with a combination of genes for the right type of trichome, with genes needed to make the insecticide, and genes that are needed for a high production and excretion. Most of these genes are located all over the place in the tomato genome. Making it a big challenge to get them back in the cultivated tomato plants that makes lots of tasty tomatoes.

Literature

Eloisa Vendemiatti, Rodrigo Therezan, Mateus H. Vicente, Maísa de Siqueira Pinto, Nick Bergau, Lina Yang, Walter Fernando Bernardi, Severino M. de Alencar, Agustin Zsögön, Alain Tissier, Vagner A. Benedito, Lázaro E. P. Peres (2021) Introgression of type-IV glandular trichomes from Solanum galapagense to cultivated tomato reveals genetic complexity for the development of acylsugar-based insect resistance bioRxiv

Rodrigo Therezan, Ruy Kortbeek, Eloisa Vendemiatti, Saioa Legarrea, Severino M. de Alencar, Robert C. Schuurink, Petra Bleeker and Lázaro E. P. Peres (2021) Introgression of the sesquiterpene biosynthesis from Solanum habrochaites to cultivated tomato offers insights into trichome morphology and arthropod resistance. Planta 254, 11.

Published by Femke de Jong

A plant scientist who wants to let people know more about the wonders of plant science. Follow me at @plantandzo

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