Callus Cultures of Tomato Mutants

Callus from hypocotyl, stem, and fruit tissue of tomato mutants was grown on a complex pea extract medium. The genotypes responded differently to the levels of nutrients and stimulators or inhibitors in the medium. Hypocotyl callus of yellow (r) tomato required K 2 SO 4 for quick establishment and continued steady growth for several months; callus of this mutant could also grow with 0.5 % dimethyl sulfoxide in the medium, although growth was less than the control. The red ghost (r + gh) mutant is sensitive to a toxic component in the pea extract, and makes its best growth with the standard minerals and vitamins, but in 1/2 concentration pea extract plus 5 % coconut water. Tangerine (t), red lutescent stem (r + l 2 ), and r + gh are mutants which respond differently to thiourea: t grows about the same at all concentrations, r + gh grows best at low thiourea, and r + l 2 grows best at the specific level of 20 mg/l thiourea. The recent active t or r + l 1 and r + l 2 isolates require supplementary auxin to which the older, slow‐growing isolates do not respond. However, there is variation in growth response of different isolates of the same mutant. The several red ( r + ) cultures are similar in their slow growth, but somewhat different in responses to specific nutrients. The recent + isolate is one of the most active cultures, in comparison to the slow growth of t callus isolated in 1964. It is therefore concluded that growth is affected both by the specific requirements of the mutant and by the age and vigor of isolates.