Self-incompatibility alleles in Esatern European and Asian almond (Prunus dulcis) genotypes: a preliminary study

Almond [Prunus dulcis (Mill.) D.A. Webb. syn. P. amygdalus Batsch] is a member of Rosaceae familiy, Prunoideae subfamily. The Rosaceae family is one of the most important plant families in the temperate zone. This family includes economically important species (e.g. apple, apricot, plum, sweet and sour cherries, almond, strawberry and rose). Almond is commercially grown worldwide for its nuts. The putative origin of almond is in the arid mountainous regions of Central Asia (Grassely, 1976; Arús et al., 2009). Several wild species grow in the areas ranging from Tianshan through Afghanistan into Iran and Iraq (Grasselly, 1976; Kester & Gradziel, 1996). Almond shows gametophytic self-incompatibility (de Nettancourt, 2001), which is governed by the highly polymorphic, multiallelic S-locus. In pistils, the S-locus encodes for an S-ribonuclease (S-RNase) enzyme, which degrades RNA in self-pollen tubes and stops their growing (McClure et al., 1989). Almond is a typically outbreeding species, which has dramatic consequences on the genetic diversity of both wild growing and cultivated accessions (Szikriszt et al., 2011), similarly to other fruit species (Halász et al., 2011; Hegedûs et al., 2011). The S-genotypes have been identifi ed for many USA, Spanish, Italian and French almond cultivars (López et al., 2006). Cross-incompatibility, that means the mutual failure in the fruit set, is a well-known phenomenon in almond. Until now, more than forty self-incompatibility (SI) RNase alleles have been identifi ed (López et al., 2006; Ortega et al, 2006; Boskovic et al., 2007; Halász et al., 2008, 2010; Kodad et al, 2008). One allele, S f , allows for self-compatibility in its inactive form, while its active form is functional (Fernández i Martí et al., 2010). The application of DNA-based molecular markers allows for the early selection of the common S-alleles (Martínez-Gómez et al., 2007; Szikriszt et al., 2011). Rapid and reliable S-genotyping protocols were reported based on the PCR amplifi cation of the fi rst and the second intron regions in the S-RNase gene using degenerate primers and fragment size determination (Ortega et al., 2005). This work is the fi rst information from a comprehensive study to determine the S-genotype of some Eastern European almond cultivars and some Turkish wild growing seedlings to characterize their S-allele pool.