Identification of ACS1, ACO1 and ETR1 alleles in some indigenous apple genotypes

Ethylene is the gaseous phytohormone, which regulates a broad spectrum of developmental and physiological processes in apple, including fruit ripening. The level of ethylene in climacteric apple fruit is determined by the activity of two enzymes that are directly involved in the ethylene biosynthetic pathway: ACC synthase (the ACS gene) and ACC oxidase (the ACO gene). In apple, ACS1 and ACO1 are predominantly expressed in the ripening fruit tissue. Ethylene is perceived through the family of receptors, among which ETR1 receptor (the ETR1 gene) is one of the receptors of Subfamily I. This work is aimed at identifying the ACS1, ACO1 and ETR1 alleles in six indigenous apple genotypes from the ex situ collection of the Fruit Research Institute, Cacak, Republic of Serbia. The alleles were revealed by polymerase chain reaction (PCR) and additional restriction analysis of PCR products for ACO1 (with BamH1 and RsaI) and ETR1 genes (with RsaI, AluI and HinfI). Two alleles of ACS1 gene (ACS1-1 and ACS1-2), three alleles of ACO1 gene (a, b and c) and four alleles of ETR1 gene (a, b, c and d) were identified. The polymorphisms observed upon PCRs and subsequently digestion with restriction enzymes were generated in two genotypes for ACS1 (ACS1-1/1 and ACS1-1/2), three genotypes for ACO1 (aa, ab and ac) and three allelic constitutions for ETR1 gene (aa, b,a/c and d, a/d).