Implementation of molecular marker technologies in the Apple Rootstock Breeding program in Geneva - challenges and successes.

摘要

The GenevaReg. Apple Rootstock Breeding program was initiated in the early 1970s with the overarching goal of developing disease resistant, productive and precocious apple rootstocks. Near the turn of the century the program was joined by USDA ARS and in addition to focusing on releasing improved rootstocks it took on the challenge of implementing molecular marker technologies to aid in the active breeding and release process. The first step was to characterize current genetic resources in the elite gene pool of the program and place them in context of other rootstock breeding programs and the larger Malus gene pool. This step yielded knowledge about the uniqueness of the germplasm that Dr. Cummins had created and opportunities for novel germplasm to be implemented. The second step was to gather phenotypic information about different half sib populations within the breeding program to identify the best parents. This was followed by a series of controlled crosses where the progeny was used to discover marker-trait associations. Conversely existing half sib breeding populations were also used for marker-trait association discovery. The main goal and third step of this effort was to implement Marker Assisted Breeding which for traits such as dwarfing and precocity could save several evaluation years in the breeding program. It turns out that in the meantime the most useful implementation of marker technologies has been the ability to fingerprint apple rootstocks with mistaken identity resulting from mixed propagation beds, or tissue culture mistake. We are currently developing a marker assisted breeding protocol that will streamline the breeding process, hopefully yielding more diverse productive rootstocks, resistant to biotic and abiotic stresses and adapted to modern orchard management practices.