Occurrence and Cause of Shoot-tip Necrosis in Shoot Cultures

Abstract

A shoot-tip necrosis in actively-growing shoot cultures of various species has been observed. Using 3 cultivars of Solatium tuberosum grown on media differing in Ca concentration (0.3, 3.0, and 30 mm Ca), typical necrosis was induced or suppressed. Potatoes at 0.3 mm contained about 0.1% Ca g¹ dry weight of shoot and also showed the highest incidence of shoot-tip necrosis, ranging from 48% to 72%, depending on the cultivar. Potatoes grown at 3 or 30 mm Ca contained 0.5% or 3% Ca g⁻¹ dry weight of shoot, respectively, and showed only 0% to 9% necrotic shoots, depending on cultivar. In addition to medium Ca content, Parafilm used as the vessel closure promoted shoot-tip necrosis, but increased levels of Ca in the medium tended to overcome the effect. Although cultivar differences in tissue content of other minerals were apparent, these were not associated with the shoot-tip necrosis problem. We conclude that shoot-tip necrosis is associated with a Ca deficiency in actively-growing shoot cultures.