The objectives of this study were to understand the role of ethylene and nutrients (Ca2+,Mg2+, K+ and N) on bitter pit (BP) development in wild type (GS) and ethylene suppressed (68G and 103Y) Greensleeves apples. The transgenic line 68G is suppressed for 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO) and line 103Y is suppressed for ACC synthase (ACS). Suppression of ethylene biosynthesis reduced BP incidence and severity. Lower ethylene biosynthesis, in ethylene-suppressed genotypes, had no effect on Ca2+, Mg2+, K+ and N concentrations in fruit cortical tissue. In all genotypes, fruit with BP had lower Ca2+ and higher Mg2+ concentrations and higher Mg2+/Ca2+ ratio in cortical tissue. The results indicate that high levels of ethylene biosynthesis and Mg2+ in cortical tissue can enhance fruit susceptibility to BP incidence
