Differential Tolerance of Cotton (Gossypiumsp.) Cultivars to the Herbicide Prometryn

• Published in: Pesticide biochemistry and physiology 1996-09, Vol.56 (1), p.1-11
• Main Authors: Molin, William T., Khan, Rehana A.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Chemical control; Fundamental and applied biological sciences. Psychology; Parasitic plants. Weeds; Phytopathology. Animal pests. Plant and forest protection; Weeds
• ISSN: 0048-3575; 1095-9939
• DOI: 10.1006/pest.1996.0054

Cotton cultivars with high tolerance to prometryn were identified in greenhouse evaluations at rates from 0.3 to 13.4 kg ha−1. Pima S-7 (Gossypium barbadenseL.), a representative of prometryn-tolerant cultivars, was reduced in growth by 40% at a preplant incorporated rate of 13.4 kg ha−1. Delta Pine 5415 (G. hirsutumL.), a representative of susceptible cultivars, was inhibited by 60% at 1.3 kg ha−1and seedlings died at 2.7 kg ha−1. The basis for cotton tolerance to prometryn was explored by determining prometryn uptake, translocation, metabolism, or effects on photosynthtic electron transport in the Pima S-7 and DP 5415 cultivars. Uptake and translocation studies showed more accumulation of14C-prometryn in cotyledons of DP 5415 than Pima S-7 on a fresh weight basis, although the reverse was found in hypocotyls. Metabolism of prometryn was detected in both cultivars, but was slow with greater than 80% of parent compound remaining in the plants after 7 days of treatment. Gland densities were determined in both cultivars, but were not sufficiently different between cultivars to account for the tolerance. Indirect measurements of the effect of prometryn on photosynthesis, as measured by nitrite reduction and reduction in sensitivity to paraquat, indicated that each cultivar was equally sensitive to prometryn. The decrease in photochemical yield of DP 5415 by prometryn was greater than in Pima S-7. The photochemical yield of Pima S-7 also recovered faster and to a greater extent than DP 5415 during a 30-min dark adaptation period. These results indicated that tolerance of Pima S-7 to prometryn was at the level of the photosynthetic electron transport system and perhaps due to differences in endogenous protection or repair mechanisms.