Seed of California almond [Prunus dulcis (Mill.) D.A. Webb, syn. P. amygdalus Batsch, and P. communis (L.) Arcangeli, non-Huds.] genotypes contained very low saturated fatty acids, high monounsaturated fatty acids, and low polyunsaturated fatty acids. Kernel oil consisted primarily of five fatty acids: palmetic, palmetoleic, stearic, oleic, and linoleic. Linolenic acid was only present in amounts of <0.02% and only in a few samples. Small but significant differences among genotypes and sampling sites were found in the proportions of palmetic, palmetoleic, and stearic fatty acids. The major differences in fatty acid composition among genotypes was found in the proportions of oleic, a monounsaturated fatty acid, and linoleic, a polyunsaturated fatty acid. The proportion of oleic acid was highest, ranging from ≈62% to 76%, and was highly and negatively correlated with linoleic acid levels. Usable genetic variation and a significant genotype × environment interaction were identified for oil content and composition. The introgression of new germplasm from peach and related species does not appear to reduce oil quantity or quality, and may offer opportunities for further genetic improvement of kernel oil composition.
Amplified fragment length polymorphism (AFLP) analysis is a rapid and efficient method for producing DNA fingerprints and molecular characterization. Our objectives were to: estimate genetic similarities (GS), marker indices, and polymorphic information contents (PICs) for AFLP markers in almond cultivars; assess the genetic diversity of almond cultivars and wild species, using GS estimated from AFLP fingerprints and molecular characterization; and facilitate the use of markers in inter-specific introgression and cultivar improvement. The genetic diversity of 45 almond cultivars from Iran, Europe, and America, were studied assaying 19 primer combinations. In addition, several agronomic traits were evaluated, including flowering and maturity times, self-incompatibility, and kernel and fruit properties. Out of the 813 polymerase chain reaction fragments that were scored, 781 (96.23%) were polymorphic. GS ranged from 0.5 to 0.96, marker indices ranged from 51.37 to 78.79, and PICs ranged from 0.56 to 0.86. Results allowed the unique molecular identification of all assayed genotypes. However, the correlation between genetic similarity clustering as based on AFLP and clustering for agronomic traits was low. Cluster analysis based on AFLP data clearly differentiated the genotypes and wild species according to their origin and pedigree, whereas, cluster analysis based on agronomic data differentiated according the pomological characterization. Our results showed the great genetic diversity of the almond cultivars and their interest for almond breeding.
Six cross-incompatibility groups, which contain most of commercially important California almond cultivars [Prunus dulcis (Mill.) D.A. Webb, syn. Prunus amygdalus Batch], and their self-incompatibility (S) allele genotypes are identified. Incompatibility groups include `Mission' (SaSb), `Nonpareil' (ScSd), and the four groups resulting from the `Mission' × `Nonpareil' cross: (SaSc), (SaSd), (SbSc), and (SbSd), as represented by `Thompson', `Carmel', `Merced' and `Monterey', respectively. All seedlings from the `Mission' × `Nonpareil' cross were compatible with both parents, a result indicating that these two cultivars have no alleles in common. Crossing studies support a full-sib relationship for these progeny groups and the origin of both parents from common germplasm. Cultivars in these six groups account for ≈ 93% of present California production, a result demonstrating a limited genetic base for this vegetatively propagated tree crop.
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