How apples may lose their pips

Researchers in New Zealand have cloned and characterized a gene which, when disrupted, allows apples to develop without seeds. This highly prized trait, fully developed in only a handful of other fruits, has proved a big bonus for growers and consumers alike. What's more, in apples the phenotype might offer other potential advantages for growers of this often difficult crop. Thousands of apple varieties have been bred over the centuries but almost all need to be pollinated and develop seed to produce fruit. But a handful of non-commercial mutants produce fruit without these requirements. Genetic control of fruit production without seeds is poorly understood but studies suggest that this trait in apples may result from the influence of a single recessive gene. The mutant flowers produced by these rare variants show strong resemblance to Arabidopsis flowers carrying the pistillata (pi), mutation. considered whether the apple gene may be equivalent to the PI gene of Arabidopsis. Analysis of three varieties of mutant apples compared to standard seeded varieties revealed that a cloned gene, MdPI, a member of the MADS-box transcription factors, was the apple homolog of PI. Mutations blocking the function of this gene were found in in each of the three mutant varieties compared with commercial, seeded varieties. This finding suggests that genetic modification to suppress expression of this gene may provide a shortcut to seedlessness in commercial varieties, avoiding lengthy, conventional plant breeding. It might also help lessen another bugbear: seed development appears to suppress next year's flowers leading to biennial cropping. As any modified varieties should produce no seeds, this problem might be avoided. The seedless fruit also appears to be much less susceptible to the codling moth, a major pest of conventional fruit. The prospect of a barren apple may be a boon indeed. Pips away: new work suggests that suppression of a single gene may be sufficient to develop seedless apples.