Fewer than 70 Albertina Sisulu orchids are left; researchers say fungi key to saving the species

The Albertina Sisulu orchid was described as a new species in 1955, the same year the struggle stalwart launched the Freedom Charter with her compatriots in the ANC Women’s League. Researchers at the University of Pretoria want to help save this endangered plant by understanding the unique fungi it depends on for survival.

Dr Tanay Bose, a postdoctoral fellow UP’s Forestry and Agricultural Biotechnology Institute (FABI), co-supervised Modjadji Makwela’s research on the orchid’s fungi, which was published in the South African Journal of Botany.

They studied the plant’s mycorrhizosphere, which refers to the soil in which the orchid’s roots and fungi (known as mycorrhizae) share nutrients to support each other.

“If this population is lost, the orchid species will be lost forever— extinct,” says Bose of the only 68 plants known to exist. The critically endangered plant appears on the South African National Biodiversity Institute’s (SANBI) redlist, with just over 60 plants found at the Walter Sisulu Botanical Gardens, the last place it can be found anywhere in the world.

As these plants are so rare, researchers had to carefully collect the soil around the plants so as not to disrupt them or destroy them in any way.

“With the help of the Wild Orchid Society of Southern Africa (WOSA) Andrew Hankey from the Walter Sisulu Botanical Garden, we collected soil samples near the plants where the orchid is not known to grow, and some soil samples close to the plants”, says Bose.

After extracting DNA from the soil samples, the researchers identified the populations of fungi types unique to the mycorrhizosphere surrounding the Albertina Sisulu orchid.

“We’ve now got a rough idea of the mycorrhiza, or fungi, but we could not identify them at the species level,” says Bose. This map of fungi surrounding the orchid can tell the researchers the exact concoction needed to help the orchid develop when it is planted in other areas to conserve it.



 

The orchid relies on the symbiotic relationship it has with its unique ecosystem of fungi, since its seeds lack an endosperm, the flashy encasing that gives other plant seeds the nutrients it needs to germinate.

“The billions of seeds each plant produces need to be infected by a specific kind of mycorrhizae to germinate and keep growing throughout its life,” says Bose. And, in turn, the orchid completes the symbiotic relationship by giving the fungi the carbon it needs to survive.

The Albertina Sisulu orchid is unique in that it has this particular set of conditions currently only found in this small area in Gauteng, but the secret to saving it from extinction might lie in this soup of fungi researchers are slowly learning more about.

Moving forward, Bose says researchers must now investigate the roles different fungi play in the orchid’s mycorrhizosphere. They need to find out which ones are beneficial to the plant, which ones are beneficial to each other, and what balance is best for this unique ecosystem.

 

Dr Tanay Bose ScienceLink Photocredits: Andrew Hankey and Karsten Wodrich

July 12, 2022

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