S-GENOTYPING OF HUNGARIAN AND EASTERN EUROPEAN APRICOTS

Apricot (Prunus armeniaca L.) shows gametophytic self-incompatibility, controlled by a single locus with eight described allelic variants. An allele for self-compatibility (S_C) allows self-fertilisation, whereas seven alleles for self-incompatibility (S₁-S₇) arrest pollen tube growth if the same allele is present both in pollen and pistil. Twenty-three apricot accessions were analysed for stylar ribonucleases by non-equilibrium pH gradient electrofocusing (NEpHGE) and by S-haplotype-related PCR amplification. NEpHGE revealed 13 bands from cultivars not genotyped previously, corresponding to putative new S-alleles, provisionally labelled as S_A-S_N. Three previously-described self-incompatibility alleles, S₁, S₄ and S₇, seem, possibly, to be present also in these cultivars, but this must be confirmed by test pollinations. Alleles S₃, S₅ and S₆ were not available, but even if three other bands were found to be identical with any of the remaining 10 alleles in the future, seven new S-alleles were found in apricot. The S-RNase isoenzyme pattern showed a good correlation with the PCR data obtained by cherry consensus primers. From a theoretical point of view, this provided further support to the hypothesis that the S-RNase gene family within the Rosaceae has been highly conserved in the course of evolution. A new set of degenerate primers (EM) detected each tested S-allele, thereby confirming further the S-genotypes assigned by combining the results of protein and DNA-based methods. This is the first study providing evidence that, similarly to other Prunus species, the S-locus of apricot is more variable than was previously considered.