Identification of Self-Incompatibility (S-) Genotypes of Iranian Almond Genotypes and Cultivars using PCR

Almond (Prunus dulcis [Webb] D.A. Mill) is an economically important species of genus Prunus (Rosaceae, subfamily Prunoideae). The commercial edible part of almond fruit is kernel. Fertilization is essential for nut production in almond but most cultivars are self or even cross-incompatible. Self-incompatibility in almond is gametophytic and controlled by a single S-locus with multiple codominant alleles. Determination of S-genotype in almond is necessary for orchard design and also for choosing parents in breeding programs. In this study, S-genotypes of seventy Iranian almond accessions as well as sixteen foreign cultivars (as standard) were amplified by using the degenerate consensus primers. The PCR products separated on agarose gel. Sizes of bunds were estimated by comparison with both reference alleles in standard cultivars and 1 kb DNA ladder. According to the results, cultivars Rabie (S7S27), Yalda (S1S7), Harir (S4S24), Sahand (S1S2), Monagha (S7S14), Khorshidi (S4S8), Shirbadam (S2S4), Shamshiri (S7S24), K-10-15(S8S9), A-92 (S8S23) showed two S-alleles. Twenty genotypes and cultivars showed one band of known S-allele and one band different to known S-alleles in reference cultivars. These new bands need to be identified through full sequencing. Mamaei, Safied and Tejari cultivars had S25, S7, S24 alleles and also one new band in sizes of 1250, 1000 and 1065 bp respectively. Totally eight new bands were amplified among cvs that were different in size from those alleles observed in reference cultivars. Alleles S4, S1, S24, S7, S12 and S2 had the highest frequencies in Iranian almonds. Combinations of these primers are useful for S-genotyping in almond germplasms.