Transfer of the ripening gene from the cultivar alcobaca (u+) to standard varieties by backcrossing has been impeded by the difficulty of identifying the gene without a test of shelf life. By the time shelf life tests are over, the plants are dead. The close linkage of alcobaca with uniform (u+), in repulsion, provides a useful marker, but only with uu lines as the recurrent backcross parent.
We found that the cultivar Garden Peach, when crossed to alcobaca, produces an F1 with long-shelf life and reduced ripening ability. In 44 F2 plants, no segregation for major shelf life genes is seen. Thus, Garden Peach apparently carries a gene for long shelf life that may be allelic with the gene from alcobaca. Furthermore, the latter is in coupling phase with uniform (u).
Using Alcobaca and Garden Peach selectively, it is possible to transfer the gene for long shelf life into any variety without blind backcrosses or F2's as follows:
1. If the cultivar is uniform ripening (u), one can cross with alcobaca (u+) and select each generation for u+ for the following backcross.
2. If the recurrent cultivar possess green shoulders (u+) one can cross to Garden Peach (uu), selecting each generation for u+ for th following backcross.
In both cases verification of the presence of alc is necessary. The F1 fruit containing either alc or alc^2 can be verified by its firmer and longer lasting fruits. Verifications, however, can continue after the cross is made.