Any search for antibiotic resistant mutants in plant cells begins by determining what concentration of antibiotic can be tolerated by normal cells. When cleocin and streptomycin are added to tomato callus media, greening of the callus is prevented. The minimum inhibitory concentration (MIC) of antibiotic must be determined before screening for mutant cells which can become green at higher antibiotic concentrations.
Callus of the following genotypes were grown on MS media which induce greening of cultured cells: L. pennelli LA 716, L. esculentum cv. Tiny Tim, and F1 hybrids of L. esculentum cv. Big Early and Tiny Tim and L. pennelli. In several trials, various concentrations of cleocin and streptomycin were added to the medium. The results in the table show the highest concentration of antibiotic at which the callus could green, followed by the concentration at which the callus still grew, but remained white. Differences in the concentrations which inhibit greening in genotypes carrying L. esculentum cytoplasm and L. pennelli are evident. However, further genetic analysis is necessary to determine whether cytoplasmic and/or nuclear genes are responsible for this phenotypic difference.
MIC of Cleocin and Streptomycin on tomato Callus
Species ug antibiotic/ml media Green/White
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STREPTOMYCIN
L. pennellii exp. 1) 0,19,37,56,74 0/19
2) 0, 5110915,20,30 5/15
3) 0, 5,15 5/15
4) 0, 5,10,15 15/-
Tiny Tim exp. 1) 0,19,38,56,74,148 0/19
2) 0,19,38,56,74,148 0/19
3) 0,10,20,30,45, 60 0/10
BEXLp 1) 0,5,10,15 0/5
2) 0,5,10,15 0/5
RCXLp 1) 0,5,10,15 0/5
2) 0,5,10,15 0/5
CLEOCIN
L. pennellii exp. 1) 0,2,4,6,8,10 8/10
2) 0,2,4,6,8,10 6/10
Tiny Tim exp. 1) 0,2,4,6,8,10 0/2
2) 0,2,4,618)10 0/2
BEXLp 1) 0,2,4,6,8,10 0/2
2) 0,2,4,6,8,10 0/6
RCXLP 1) 0,2,4,6,8,10 0/2
2) 0,2,4,6,8,10 0/2