A Proposed Natural Genetic Solution to the Long Juvenility Problem in Apple

From a tree fruit breeder’s perspective, long juvenility represents a significant challenge. Because breeders can only make crosses once trees reach maturity and start to flower, they must often wait through a multi-year juvenile phase before evaluating fruit and making further crosses. Within wild relatives of apple, much useful natural variation exists in length of juvenility. However, the genes and their allelic variation governing the transition from the juvenile to adult phase are not as well elucidated as other valued traits for breeding. Some cross-compatible apple wild relatives transmit short-juvenility alleles to offspring. To identify these genetic factors and their underlying genes, derived families exhibiting variation for length of juvenile phase are needed for QTL analyses. The existing natural genetic variation might then be exploited for apple breeding. Combining genetic factors associated with short juvenility from several distinct sources holds promise for achieving ultra-short juvenility naturally to overcome the problem of long juvenility in apple.