Identification of S-haplotype-specific S-RNase and SFB alleles in native Chinese apricot (Prunus armeniaca L.)

Abstract

SummaryChinese apricot (Prunus armeniaca L.) shows gametophytic self-incompatibility (GSI) controlled by a single locus containing at least two linked genes [i.e., the S-RNase gene and the pollen-expressed SFB (or SLF) gene] as do other fruit species in the family, Rosaceae. To elucidate the S-genotypes of 14 native Chinese apricot cultivars, PCR was performed using primers designed from Prunus S-RNase and SFB consensus sequences. After cloning and sequencing the PCR products, the S-genotypes of all 14 apricot cultivars were determined, and eight new S-RNase alleles and nine SFB alleles were identified. The S-RNases shared typical structural features with S-RNases from other Prunus spp. exhibiting GSI. The SFB genes showed similar structural characteristics to SFB genes in other Prunus spp. The intron sequences of the SFB genes revealed sequence and length polymorphisms. The deduced level of amino acid sequence identity for the eight new S-RNase alleles was 66.4 – 100% in P. armeniaca, while the similarity of the SFB alleles was 73.7 – 98.6%. The physical distances between the SFB and S-RNase genes was determined exactly in the S9,S11,S17, and S26-haplotypes, confirming that the S-RNase and SFB genes were linked. The range of distances between the two genes was 299 – 1,061 bp. This study increases our knowledge on the S-genotypes of apricot native to China, and enriches our genomic information on GSI in the Prunus genus.