Millions of years after their ancestors parted company on the northern shores of Australia, two world-roaming plants have been sexually reunited by biodiversity researchers from Australia and the United States.
"It's a bit like a botanical version of Wuthering Heights," said CSIRO scientist Dr Tony Brown. "Millions of years ago the ancestors of these two species were wrenched apart. Now science has brought them back together."
Biodiversity researchers hope the new cross, between soybean and a wild Australian plant called woolly glycine, will give rise to a new type of soybean which can live in salty and dry areas and which is resistant to diseases like rust.
"I don't think most Australians realise that our native plants include many relatives of important world crops," Dr Brown said. "Such wild biodiversity is an important source of new genetic material for world agriculture."
The ancestor of the soybean and its Australian cousins probably evolved in South East Asia, tens of millions of years ago. Then Australia was much further south, near Antarctica, but was very slowly drifting north. About 15 million years ago Australia's continental plate collided with South East Asia. The soybean ancestor was one of many Asian plants which jumped ashore in Australia.
The rest is history. From the plants which stayed in South East Asia a wild type of soybean evolved, which was domesticated in China around 1,100 BC to become one of the world's most important food crops. Meanwhile in Australia the soybean's ancestor evolved into at least 16 different species, growing everywhere from Alice Springs to the Alps.
Woolly glycine (Glycine tomentella) is a short, twining, perennial with purple to reddish pea-like flowers. It lives in open eucalypt woodland in northern Australia, from Grafton on the New South Wales north coast up to Cape York Peninsula, and as far west as Katherine in the Northern Territory and Broome in Western Australia.
As it evolved to suit Australian conditions, woolly glycine learned many useful new tricks like how to survive droughts, how to live in salty soil (it even grows on some beaches) and how to resist the damaging crop disease rust.
"The Australian Glycine species represent a precious genetic resource for one of the world's most important crops," Dr Brown said. "They show just how valuable Australia's native biodiversity is to the world - we have species growing wild on this continent which carry all kinds of useful genes."
Dr Ted Hymowitz from the University of Illinois in the US has spent 15 years trying to produce a soybean-like descendant through cross-breeding woolly glycine with soybean. This year for the first time he finally succeeded in breeding fertile soybeans containing genes from the Australian plants.
The breakthrough required painstaking laboratory work, using a variety of woolly glycine found by the CSIRO on Queensland's Brampton Island in 1976. Dr Brown will now work with Dr Hymowitz to test whether the resulting plants have inherited rust-resistance from their Australian ancestor.
The US harvests about eight million hectares of soybean each year. Australia imports about $20 million worth of soybean a year, mostly from the US. But Australia now has a growing soybean industry of its own in northern NSW and Queensland.
Soybean rust is a major problem throughout Australia's region, with growers in Taiwan, Indonesia, Thailand, and South America seeking ways to combat the disease. Australian growers also suffer from rust, although it usually strikes too late in the season to be a major problem. The US is so far free of the disease, but scientists there are concerned about the vulnerability of their crop.
Biological diversity (or "biodiversity") means simply the variety of life on Earth. It includes three levels - genetic variation within a species, variation between different species and variation between different ecosystems.
World agricultural trade, worth an estimated $3 trillion a year, depends on new varieties of livestock and crops being bred continually from their wild cousins. Scientists use wild genetic stocks to keep domesticated crops and animals a jump ahead of pests and diseases, to breed drought-resistance and other desirable traits, to boost nutritional content and to increase crop yields.
Australia, with an estimated 475,000 of the Earth's 10 to 30 million species, is one of the world's 12 "megadiverse" countries. Australia's Federal, State and Territory governments are now close to finalising a strategy for conserving biodiversity.
Examples of some Australian Glycine plants are now in flower and can be photographed or filmed at the CSIRO Division of Plant Industry, Black Mountain, ACT. Dr Brown also has seeds of the new cross-bred plant for photographing.
Author: David Mussared
Source: Department of the Environment and Water Resources. December 23, 1993.