Custard apple could be top banana

UC DAVIS (US) —What has been called “the most delicious fruit known to man” the cherimoya or custard apple, is tainted by a preponderance of seeds—but plant scientists may have figured out how to get rid of them.

“This could be the next banana—it would make it a lot more popular,” says Charles Gasser, professor of molecular and cellular biology at the University of California, Davis. All commercial varieties of banana are seedless, but the fruit has up to 100 seeds in its natural state.

The research is published in the journal Proceedings of the National Academy of Sciences.

Researchers studied a close cousin of the cherimoya, a seedless variety of the sugar apple, and discovered its ovules lack an outer coat. Ovules are what would normally form seeds.

They looked similar to the ovules of a mutant of the lab plant Arabidopsis in which defective plants don’t make seeds or fruit.

But the mutant sugar apple produces full-sized fruit with white, soft flesh without the large, hard seeds. The same gene was responsible for uncoated ovules in both the Arabidopsis and sugar apple mutants.

“This is the first characterization of a gene for seedlessness in any crop plant,” Gasser says.

Seedless varieties of commercial fruit crops are usually achieved by selective breeding and then propagated vegetatively, for example through cuttings.

Discovery of this new gene could open the way to produce seedless varieties of sugar apple, cherimoya, and perhaps other fruit crops.

The discovery also sheds light on the evolution of flowering plants. Cherimoya and sugar apple belong to the magnolid family of plants, which branched off from the other flowering plants quite early in their evolution, Gasser says.

“It’s a link all the way back to the beginning of the angiosperms.”

The work was funded by the Spanish government, the European Union, and the National Science Foundation.

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