Differential Tolerance of Tomato Cultivars to Metribuzin

Abstract

Seedlings of fifteen different cultivars of tomato ( Lycopersicon esculentum Mill.) varied greatly in tolerance to metribuzin [4-amino-6-tert-butyl-3-(methylthio)- as -triazine-5(4 H ) one] applied at a concentration of 0.5 mg/L in quartz sand nutrient culture during the three-true-leaf stage. Tolerance increased with seedling age, but acceptable tolerance was observed about 6 days earlier in the tolerant ‘Fireball’ compared to the susceptible ‘Heinz 1706′. Root uptake and acropetal translocation of metribuzin-carbonyl- 14 C was similar in 2-week-old seedlings of susceptible Heinz 1706 and tolerant Fireball seedlings. Differential tolerance was related to the rate of detoxification by metabolism within the tomato leaves, which was approximatley two-fold greater in the tolerant Fireball seedlings.