Shotgun weddings leading to useful new hybrids

You're a plant geneticist, and you want to extend the range of the world's most important human food crop, rice (Oryza sativa) into cooler regions of the world.

You've tracked down a North American cousin of rice, Zizania, that flourishes on the margins of seasonally frozen lakes; it obviously offers some very good cold-tolerance genes. But even the most advanced hybridisation techniques fail -- genetically, they're an ocean apart.

There's another option, says Dr Rob Henry: a shotgun marriage, using Southern Cross University's patented WideHyb technology.

WideHyb is Henry's innovative new application of biolistics, which employs a modified rifle to fire tiny DNA-coated, microscopic particles or tungsten or gold through plant cell walls.

Rather than punctuating plant cells with one or two well-aimed genes of known function, WideHyb involves shooting in the dark, and asking questions later.

Henry said microprojectiles were coated with DNA fragments that collectively spanned the entire genome of the wild variety. Each recipient would contain a package of anonymous transgenes, potentially detectable through their effect on the phenotype of the host -- such as new-found cold tolerance.

Large populations of the 'shot' plants, containing different DNA sequences from the wild relative, would then be exposed to chilling as seedlings, to identify the most cold-tolerant lines.

"We developed wide hybridisation working on rice, because we were an early leader in transforming rice," Henry said. "It's a very useful technology for going beyond normal hybridisation barriers."

He said the technique was applicable to almost any crop, including wheat. His research group was exploring its potential for domesticating wild genes from relatives of sugar cane. Legumes are another potential target.

Henry said the North American wild rice Zizania, in a different genus but the same botanical tribe as Oryza, was not only a potential source of cold-tolerance and disease-resistance genes, but could also endow cultivated O. sativa and O. indica varieties with novel flavours.

The Australian wild rice O. potamophila, which grows in the shallow margins of northern NSW rivers, was another potential source of genes for extending rice's environmental tolerance, Henry said.