The hot, dry desert environment has led to large genetic differences between male and female jojoba plants, a discovery that could boost jojoba production and shed light on how plants adapt to environmental stress.
A team of researchers in a collaboration between King Faisal University and the University of Queensland has identified a wide divergence of sex chromosomes in jojoba.
Professor Robert Henry, research director for the Queensland Alliance for Agriculture and Food Innovation at UQ, said most plants were hermaphroditic and contained both male and female parts.
“Only six percent are dioecious, like jojoba, requiring both a male plant and a female plant to reproduce.
“Jojoba plants reproduce sexually, as humans do, but the male and female genomes in humans are 99.9% identical, whereas in jojoba there is something like a difference in 15%.
“People say men are from Mars and women are from Venus when there is a genetic difference of 0.1 between the sexes, but male and female jojoba plants have diverged so much more genetically – the harsh environments in which they are. grow resulted in the plant having more new sex genes than any other known living organism. “
The discovery could help researchers develop a DNA test to identify male and female jojoba plants, which cannot be distinguished from each other as seedlings.
Jojoba oil is derived from the liquid wax of the female seed Simmondsia chinensis plants, a shrub native to the deserts of North America.
The plant is known for its tolerance to high temperatures and high salinity, and its oil is used in skin care and pharmaceuticals, with applications for medical and industrial products.
Only female plants bear seeds.
“As mature plants, the male and the female are very different,” said Professor Henry.
“The females are bigger, the males tend to be smaller and differently shaped plants.
“Females have much deeper root systems.”
Professor Henry said that a problem for jojoba growers is that although in nature the growth ratio of male-female jojoba plants is similar, in growing systems five times more males than males. females were produced.
“Growers don’t want to plant males – they have to dig up male plants and replant,” he said.
“This is not a good use of resources in a difficult growth environment.”
Professor Henry said male and female jojoba plants may have evolved in response to different demands for allocating reproductive resources under the stress of the desert environment.
“The male-specific regions included many genes related to flowering and the stress response,” he said.
Female plants devote resources to seed production, and greater root growth allows female plants to establish for the longer growth phase required to support seed production.
The global jojoba oil market is growing at a rate of 8.4% per year.
The main jojoba producing regions in Australia are the plains of west-central New South Wales and southern Queensland.
The United States of America accounted for 39% of jojoba production in 2019 – Mexico, Israel, Chile and Argentina are other major producers.
Jojoba is also being planted in Saudi Arabia on the King Faisal University campus with plans for large-scale plantings.