Submitted to: Options Mediterraneennes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 6, 2008
Publication Date: December 1, 2010
Citation: Ledbetter, C.A. 2010. Almond breeding and evaluation activities in central California: past and future. Options Mediterraneennes. 94:255-260. Interpretive Summary: An increasing worldwide demand for almonds has directed California growers to new plantings of almond orchards at an unprecedented rate. It is estimated that 75% of the US bee supply is currently needed to meet pollination requirements for the California almond crop. The new orchards add to future pollination requirements, and beekeepers now question the adequacy of future bee supplies to meet the needs of almond growers. In 1993, we began developing almond trees that do not require bees to ensure pollination and nut set by breeding our California almonds with a Spanish almond named Tuono. The ‘self-fertility’ of the Spanish Tuono was well known, but Tuono’s almonds do not have the nut qualities present in California varieties. By breeding the California almonds with Tuono and selecting those nut types preferred by processors and consumers, new almond varieties can be created that can set a crop of nuts without the beekeeper’s help. We are beginning to test the yield potential of some of these new self-fertile almonds. Given that their potential yields are adequate to meet grower needs, almond producers will be the predominant beneficiaries of this research. Utilization of self-fertile almond varieties will reduce the cost of producing almonds by eliminating the ever-increasing costs associated with bee rental during the busy pollination season.
Technical Abstract: Almond breeding and evaluation efforts at the Agricultural Research Service resumed during the late 1980s after a lapse of nearly 20 years. Breeding efforts from the 1950s through the early 1970s led to a diverse collection of advanced selections, some being suitable as pollenizers for the important Nonpareil cultivar. Current evaluation efforts are now further characterizing the collection, and some selections are being used in a new breeding effort to develop self-compatible almonds. Through K-means analyses, we have identified those advanced selections from the former breeding effort that were most similar to Nonpareil in bloom phenology and nut/kernel characteristics. In long term storage trials, we have identified several advanced selections with reduced pellicle luminosity degradation rates as compared with Nonpareil. The Tuono cultivar has been our exclusive source of self-compatibility in the new breeding effort, with planned hybridizations emphasizing those advanced selections that are homozygous for sweet kernel. New self-compatible accessions are being identified in segregating seedling populations, and we currently evaluate 50 – 70 self-compatible accessions annually for nut/kernel quality. Recent evaluation efforts have demonstrated significant differences in shell cracking strength among almond varieties that are independent of an accession’s kernel percentage, suggesting shell compositional or morphological differences. These differences may have implications in the use of specific shell types for granular activated carbons, or other value-added product applications.