Genetic characterization and relatedness among California almond cultivars and breeding lines detected by randomly amplified polymorphic DNA (RAPD) analysis

Almond [Prunus dulcis (Mill.) D.A. Webb, syn. P. amygdalus, Batsch; P. communis (I.) Archangeli] represents a morphologically and physiologically variable group of populations that evolved primarily in central and southwest Asia. California cultivars have been developed from highly selected subgroups of these populations, while new breeding lines have incorporated germplasm from wild almond and closely related peach species. The genetic relatedness among 17 almond genotypes and 1 peach genotype was estimated using 37 RAPD markers. Genetic diversity within almond was found to be limited despite its need for obligate outcrossing. Three groupings of cultivar origins could be distinguished by RAPD analysis: bud-sport mutations, progeny from interbreeding of early California genotypes, and progeny from crosses to genotypes outside the California germplasm. A similarity index based on the proportion of shared fragments showed relatively high levels of 0.75 or greater within the almond germplasm. The level of similarity between almond and the peach was 0.424 supporting the value of peach germplasm to future almond genetic improvement.