New approaches to almond breeding at the University of California-Davis program

Abstract

The breeding program in the Department of Pomology at the University of California at Davis is one of the largest and oldest continually active almond improvement programs in the world. In this study, current strategies for almond improvement, including germplasm improvement, propagation techniques and use of molecular markers, are described. In germplasm improvement, the introduction of genes from related Prunus species conferring several potentially useful traits (including self-compatibility, improved growth habit, drought resistance, kernel quality) is being pursued. Twin seeds (two embryos within the same seedcoat that occur spontaneously in certain almond cultivars) produce seedlings with unusual growth and development. Plants appear to be aneuploid, which, if confirmed, would be very useful for genetic studies (isolation and sequencing of genes, genetic transformation, etc.). Propagation methods employed include in-vivo micrograft techniques that allow the early propagation and invigoration of weak material. In addition, the growth of seedlings in controlled environments, including the induction of an artificial rest period (in cold chambers), provides a strategy for obtaining vigorously growing plant tissue throughout year. Molecular markers have become a essential tool in breeding. In our assays, different types of molecular markers (isozymes, PCR, SSRs and AFLPs) have been employed for the genetic characterization of plant material and the linkage of traits with agronomic interest, and the establishment of genetic relationships between cultivars and species.