Effect of medium pH on shoot regeneration from the cotyledonary explants of tomato

To optimise medium pH for in vitro shoot regeneration and shoot growth from the cotyledon explants of tomato cv. Red Coat, the explants were innoculated onto MS medium which was maintained at a wide range of pH (4.5-7.5). Percentage shoot regeneration and number of shoots produced per explant were not significantly affected by the medium pH. The proportion of explants that produced callus and callus diameter remained unaffected by the medium pH. In contrast, the shoot height was significantly affected and taller shoots were only produced at a pH range of 5.5-6.0. Lower (4.5-5) and higher (6.5-7.5) medium pH significantly reduced shoot height. The results suggest that the explants of tomato Cv. Red Coat are moderately tolerant to a wide range of medium pH, as most of the traits studied remained unaffected by the change in media pH. However, the best regeneration and growth occurred only in the pH range of 5.5-6.0.