Variability of oil content and of major fatty acid composition in almond (Prunus amygdalus Batsch) and its relationship with kernel quality.

Oil content and fatty acid composition were determined for two years in the kernel oil of eight cultivars and 47 advanced self-compatible almond genotypes developed in an almond breeding program. Considerable variation between genotypes was found for all parameters. Oil content ranged from 48% to 67% of the total kernel dry weight but was consistent over the two years. Fatty acid composition was also very variable, with significant differences between genotypes, even in genotypes of the same progeny. Oleic acid, ranging from 63% to 78%, and linoleic acid, ranging from 12% to 27%, were the major fatty acids, showing higher values in some selections than in their parents. The large variability observed for all fatty acids and the presence of selections with higher oil and fatty acid contents than the commercial cultivars represents a very promising base to obtain new almond cultivars with oil of higher quality, satisfying the industrial and consumer sectors.

Negative inbreeding effects in tree fruit breeding: self-compatibility transmission in almond.

Inbreeding depression has been observed in most fruit trees, negatively affecting the offspring of related parents. This problem is steadily increasing due to the repeated utilization of parents in breeding programmes. In almond, self-compatibility transmission from 'Tuono' to its offspring remains partially unexplained due to deviations from the expected genotype ratios. In order to test if these deviations could be due to inbreeding, the S-genotypes of the seedlings of four almond families, 'Tuono' (S(1)S(f )) x 'Ferragnès' (S(1)S(3)), 'Tuono' (S(1)S(f)) x 'Ferralise' (S(1)S(3)) and reciprocal crosses were studied. The S-genotype determination of each seedling by separation of stylar S-RNases and by S-allele-specific PCR amplification gave identical results. The ratio of S-genotypes of the family 'Tuono' x 'Ferralise' was the one least adjusted to the expected 1:1 ratio, because the number of self-compatible seedlings (S(f)S(3)) was less than a half the number of self-incompatible ones (S(1)S(3)). A mechanism acting against inbreeding would favour cross-breeding in the following generation to increase heterozygosity. This fact stresses the need to avoid crosses between related parents in fruit breeding programmes.