Plant & zo
The science of plants and more
Resistance to witchweed
Weeds are unwanted. Often, easy removed by hoeing. But it is a different story when weeds are parasitising a plant. Striga is one of these parasitising weeds. It is a real pest in sub-Sahara Africa. It parasitises crops like maize, rice, and sorghum. And it gets its nickname ‘witchweed’ from the ability of its seeds to stay dormant in the soil for up to 20 years. This makes Striga difficult to deal with. But now researchers have discovered a Striga resistance maize line.
The moment strigolactone is perceived by Striga seeds, is the moment they germinate. Strigolactones are important plant hormones that play a role in the development of the plant. They are in charge of regulating shoot branching. But they are also excreted by the plant when it wants to cooperate with fungi. Something Striga uses to germinate when a plant is near.
Because strigolactones are important, a plant cannot do without. This made the researchers look to the specific strigolactones that maize plants excreted. Hoping to find some differences. Strigolactone excretion varied a little between most of the maize plants. But there was one exception, with a completely different profile. This plant excreted the strigolactones zealactol and zealactonoic acid, but not the commonly detected zealacone.
Giving hope, that Striga resistant crops can be developed
Subsequently the researchers studied the effect of the different strigolactone composition. This they did by looking to Striga germination. When zealactone was present approximately 40% of Striga seeds germinated. But in the presence of zealactol Striga germination was reduced to approximately 10%, and in the presence of zealactonoic acid even less seeds germinated.
For the breeding of Striga resistance maize lines it is useful to know the responsible genes. As such the researchers next studied the biosynthesis of strigolactones in maize. They discovered that only one gene was important for getting less zealactone. When the researchers turned this gene off the plant produced only the Striga resistant strigolacones, but not those that enable Striga to germinate. And not unimportant, the Striga resistant maize did not show any other differences with the striga sensitive maize.
Giving hope. That it is possible to adjust the biosynthesis of strigolactones without this having a disadvantaged effect in the development of the plant. That it is possible to excrete strigolactones that do not result in Striga germination. That Striga resistant crops will be developed.
Literature
C. Li, L. Dong, J. Durairaj, J.-C. Guan, M. Yoshimura, P. Quinodoz, R. Horber, K. Gaus, J. Li, Y. Setotaw, J. Qi, H. De Groote, Y. Wang, B. Thiombiano, K. Floková, A. Walmsley, T. Charnikhova, A. Chojnacka, S. Correia de Lemos, Y. Ding, D. Skibbe, K. Hermann, C. Screpanti, A. De Mesmaeker, E. Schmelz, A. Menkir, M. Medema, A. Van Dijk, J.Wu, K. Koch, and H. Bouwmeester (2021) Maize resistance to witchweed through changes in strigolactone biosynthesis. Science 379, 94-99 DOI: 10.1126/science.abq477
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