To save endangered plant species, horticulturists use a tactic inherited from horse breeders and zookeepers and create breeding registers or “stud books” to avoid inbreeding. Of course, they start with a plant with a Latin name that means “large misshapen penis”.
In botanical gardens around the world, Amorphophallus titanum causes a sensation during its rare blooms that come when they want. Best known as a corpse flower because it smells so bad that it has the largest flower of any plant in the world. In the US, more gardens than ever before are maintaining this rare horticultural celebrity that draws many visitors to their greenhouses.
The endangered species is difficult to breed, however, and with low numbers available, there is a risk of losing the genetic diversity necessary to grow hearty corpse flowers in conservatories and possibly maintain them in the wild.
“If you don’t have a lot of genetic diversity, you can get inbreeding depression because you’re basically growing plants that are closely related to each other,” said Susan Pell, assistant director of the United States Botanic Garden in Washington. DC inbreeding can manifest itself in less viable seeds, weaker seedlings, and a decrease in the diversity of the plants’ physical properties, she said.
Efforts to preserve the corpse flower are at the heart of an initiative by the Chicago Botanic Garden to increase the chances of rare plants surviving by maximizing their genetic diversity. The project will apply breeding principles used by zoos to conserve animal species on six critically endangered plants, and hopefully prove methods that could be applied to many other plants.
“We’ve often focused on saving one species, but we haven’t focused on conserving species diversity,” said Jeremie Fant, conservationist at the Chicago Botanic Garden in Glencoe, Illinois.
The participants in the three-year project, which includes botanical gardens in Atlanta, Florida and Hawaii, are funded by a grant from the Institute for Museum and Library Services, a federal agency, and collect genetic information from each of the six species that are grown in botanical gardens around the world as well as historical information, including the provenance and age of each plant.
Once DNA has been extracted from the collected plant material, the project participants use population management software to create plant pedigrees.
“We create the family tree for each specimen,” said Dr. Fant.
Then they can identify ideal breeding matches and underrepresented genetic traits. The aim is to have a centralized pedigree database that will document pedigrees, demographics and genetics of rare plants that could play an important role in the future of efforts to protect rare plants.
The Chicago Botanic Garden currently collects genetic material from corpse flowers in 140 botanical gardens and private collections. The other five plants are: the Attalea crassispatha, a rare palm in southwest Haiti; Hibiscus waimea, a thriving member of the Kauai okra family; Magnolia stellata, a small tree from Japan, also known as the star magnolia; Magnolia zenii, an endangered species of magnolia tree from China; and Phyllostegia electra, a rare species of flowering mint only found on Kauai.
For help creating the studbooks for each plant species, the gardens turn to the Brookfield Zoo, west of Chicago. The zoo cares for 45 endangered animal species that have “species survival plans,” a significant portion of the 125 species recorded in such documents. North American zoos and aquariums are coordinating plans to manage breeding programs for selected species to maintain healthy captive populations and ensure genetic diversity.
The project developers chose the six threatened species because either their seeds cannot tolerate traditional storage conditions or because they produce little to no seeds, said Dr. Fant. Up to half of all rare plant species correspond to this description.
The six plant species were also chosen because they have grown in botanical gardens for several generations and are dependent on humans for reproduction, he said.
These criteria make the corpse flower particularly suitable for the project, as its history has been documented since 1889, when it first bloomed outside of its native Sumatra in the Royal Botanic Gardens at Kew, London. Additionally, the corpse flower, whose flowers emit a pungent odor that has been likened to the smell of a dead body to attract pollinating insects in the wild, needs human help to reproduce in captivity.
Corpse flowers need just the right temperature, light, water, and humidity to reproduce the tropical growing conditions under which the plant stores enough energy to bloom roughly once a decade, said Joyce Rondinella, senior horticulturist at Longwood Gardens, Kennett Square, Pennsylvania is not involved in the project.
Ms. Rondinella has tended the corpse flower known as “Sprout” since she arrived in Longwood from the Chicago Botanic Garden in 2018. Sprout grew over two meters tall in July 2020 and bloomed the rare plant for two days, she said.
The corpse flower could help bring much-needed attention to the importance of genetic diversity in plants, which is a global problem due to the disappearance of plant habitats, Ms. Rondinella said.
It’s about more than just smelly garden shows and ticket sales to preserve plant genetic diversity. When plant populations are too genetically isolated, species that may one day provide food or medicine for future human use can be lost.
“The more species of plants you have, the more species of insects, the more species of animals you have,” said Dr. Pell. “They are all tied together.”