New research shows how genetics can determine the sex of kiwifruit plants.

Photo / Supplied

An international research team has discovered a sex-determining gene in kiwifruit that could potentially lead to the breeding of hermaphrodite varieties.

Self-fertile kiwifruit cultivars could remove the current need for pollen supplementation, saving land and labour costs.

Since only female kiwifruit produce fruit, horticulturists have been looking for ways to find out whether their plant babies are boys or girls - but usually this relies on waiting for them to grow up.

They hope to use this to screen seedlings so they can get rid of the male plants earlier, so they don't have to waste time and water waiting to find out.

The study has also validated the "two-mutation model" in sex acquisition of plants proposed 40 years ago.

Plant & Food Research scientists and their research partners in Japan and the US identified a gene called Friendly Boy (FrBy), which is necessary for pollen production and is found naturally in Y chromosomes of male kiwifruit plants.

It is the second sex-determinant discovered in kiwifruit after Shy Girl (SyGI), which suppresses fruit production in male kiwifruit plants.

"We overexpressed the FrBy gene identified by our Japanese research partner in rapid-flowering kiwifruit plants," said Plant & Food Research scientist Dr Sarah Pilkington.

"We found that expression of FrBy in female kiwifruit resulted in hermaphrodite plants, which means the female plants could both produce and receive pollen, making them capable of self-fertilisation."

The study supports the "two-mutation model" of sex evolution in plants proposed by Deborah and Brian Charlesworth in 1978.

It suggests that at least two gene mutations, one affecting ovule (female) production and one affecting pollen (male) production, are necessary to transform a hermaphrodite species into one with separate sexes.

The results of this study pave the way for the potential development of hermaphrodite kiwifruit.

The paper "Two Y chromosome-encoded genes determine sex in kiwifruit" is published in the journal Nature Plants.