Identification of self-incompatibility S alleles in Moroccan almond (Prunus dulcis Miller) germplasm using PCR

The S-genotypes of 70 Moroccan almond [Prunus dulcis Miller (D. A. Webb)] accessions collected from different geographical regions of Morocco were determined using PCR and agarose gel electrophoresis. PCR was carried out using seven pairs of primers that amplified different regions of the self-incompatibility S-allele. The results showed that the majority of Moroccan almond accessions had heterozygous S-RNase genotypes, with a total of 109 bands. The sizes of the amplified bands were compared with known S-alleles in almond varieties and labelled accordingly. Alleles S-1, S-3, S-11, and S-13 occurred at the highest frequencies (23%, 15%, 12%, and 16%, respectively). Alleles S-4, S-9, and S-27 were not observed in the samples examined, and allele S-24 had the lowest occurrence (1%). Moreover, the Sf allele, responsible for self-compatibility in almond, was identified in three local accessions for the first time. The application of PCR to study the diversity of S-alleles in almond germplasm is discussed.