In vitro selection of tomato resistance to metribuzin herbicide : indices of tissue culture and growth parameters

Includes references.

The effect of metribuzin at different doses (0.25, 0.5, 0.75 and 1.0 kg ai ha⁻¹) was studied on mtact seedlmgs of two tomato variants (Lycopersicon esculentum Mill, cv. Karnak vfnt F-1 and Castle rock). The herbicide provoked significant inhibitions in the different growth parameters studied (shoot height, root length, fresh weight and dry weight) of the two tomato variants. The magnitude of inhibition augmented with increasing metribuzin dose. Therefore effectiveness of cyclical in vitro selection for metribuzin tolerance in both variants was studied. Cotyledons and leaf explants from shoot regenerated on media containing different concentrations of metribuzin (0, 0.63, 1.25, 2.5, 5 and 10 μM) were used to initiate three successive cycles of selection. The results indicated that there were great reductions in tissue culture parameters (tissue viability, callus initiation, callus proliferation and shoot regeneration) in the three cycles of selection. There were also significant reductions in growth parameters (shoot height, root length, fresh weight and dry weight) of the regenerated plantlets from each of the three cycles. More reduction was induced by the high concentrations. However, after three cycles of selection, the magnitudes of tissue viability, callus initiation, callus proliferation and shoot regeneration were higher in the 3rd cycle relative to the 1 st or the 2nd cycle. Thus, it could be concluded from these findings that the inhibitory influence of metribuzin upon tomato growth appeared to be retracted after in vitro selection of three successive cycles of growth suggesting an improved resistance of tomato to metribuzin.

Summary in Arabic.

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