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

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 + CaCl2 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 C2H4 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 rin 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 C2H4 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. (C) 1998 Elsevier Science B.V. All rights reserved.