Saline growing conditions induce ripening of the non-ripening mutants nor and rin tomato fruits but not of Nr fruit

Abstract

Tomato (Lycopersicon esculentum Mill.) plants cv. 'Rutgers', and their three nearly isogenic ripening mutant derivative lines nor, rin and Nr, were grown in sand culture irrigated with nutrient solution. Six-week-old plants were exposed to saline growing conditions (EC 15.5 mmohs/cm) by adding NaCl or NaCl + CaCl<inf>2</inf> to the nutrient solution. Ripening was induced in nor fruit under both saline conditions as indicated by fruit softness, red colour development, induction of a climacteric pattern of C<inf>2</inf>H<inf>4</inf> production and an increase in 1-aminocyclopropane-1-carboxylic acid (ACC) content over that of the control. Similar stimulation of all ripening parameters was obtained in tin fruit, but only with NaCl treatment. It seems that the presence of Ca²⁺ in the saline solution blocked salt-induced rin fruit ripening. Neither saline treatment affected Nr fruit ripening. Furthermore, Nr fruit grown under non-saline conditions showed yellow colour development and produced C<inf>2</inf>H<inf>4</inf> at a level comparable to that produced by 'Rutgers' fruit with no post-climacteric decline. The ACC content of Nr fruit was significantly higher than that of post-climacteric 'Rutgers' fruit. These data are discussed as to the possible role of saline treatment with or without Ca²⁺ in inducing ripening in the non-ripening mutants.