Bananas in their natural state have up to a hundred seeds but all commercial varieties that you see in stores are seedless.   Making seedless varieties made bananas wildly popular, which was good for the people who grow them and good for the people who eat them.     That is a science win.

Researchers have now discovered a way to make "the most delicious fruit known to man", as Mark Twain called it, more popular with the public also.   The cherimoya, or custard apple, has lots of big, awkward seeds but a group of researchers studied the seedless variety of sugar apple, a relative of the cherimoya, and noted that the ovules, which would normally form seeds, lacked an outer coat.

They looked similar to the ovules of a mutant of the lab plant Arabidopsis discovered by the lab of Charles Gasser, professor of plant biology at UC Davis, in the late 1990s.   In Arabidopsis, the defective plants do not make seeds or fruit. But the mutant sugar apple produces full-sized fruit with white, soft flesh without the large, hard seeds.

The Spanish team contacted Gasser, and graduate student Jorge Lora at the Consejo Superior de Investigaciones Cientificas labs in Malaga, Spain, came to Gasser's lab to work on the project. He discovered that 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 said.

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 in sugar apple, cherimoya and perhaps other fruit crops.

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

"It's a link all the way back to the beginning of the angiosperms," Gasser said.

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