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VARIATION IN (KOCHIA SCOPARIA (L.) SCHRADER) GROWTH RESPONSE TO TRIAZINE HERBICIDES
Abstract
Variation in kochia {Kochia scoparia (L.) Schrader} response to triazine herbicides was investigated in the greenhouse and laboratory. Kochia plants from railroad rights-of-way with a 13-year history of annual triazine applications were not controlled by 20 kg/ha atrazine {2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine} (atrazine resistant). These plants were considered resistant because they could no longer be controlled by atrazine dosages that were economically feasible. Kochia plants from fields nearby with no triazine history were destroyed with 2 kg/ha atrazine (atrazine susceptible). Atrazine-resistant and susceptible kochia biotypes were treated with common use rates of chloro-, methoxy-, and methylthio- substituted symmetrical triazines, an asymmetrical triazine, a substituted urea and a phenoxy herbicide. All triazines controlled atrazine-susceptible kochia but they did not control atrazine-resistant kochia. Diuron {3-(3,4-dichlorophenyl)-1,1-dimethylurea} controlled atrazine-resistant and susceptible kochia. Susceptibility to 2,4-D ester {(2,4-dichlorophenoxy)acetic acid} was greater in atrazine-resistant than in atrazine-susceptible kochia. Leaf disk and leaf infusion laboratory techniques were modified to detect atrazine resistance or susceptibility in kochia non-destructively. Only atrazine and deethylated atrazine {2-chloro-4-(amino)-6-(isopropylamino)-s-triazine} were toxic to atrazine-susceptible kochia chloroplasts. There were no significant differences in atrazine translocation to shoots or in metabolism to non-phytotoxic compounds in atrazine-resistant or susceptible kochia biotypes. Electron transport in atrazine-resistant isolated chloroplasts was not inhibited by 10('-4) M atrazine. Electron transport in atrazine-susceptible chloroplasts was stopped at 10('-5) M atrazine indicating that at least part of the mechanism of atrazine resistance in kochia is at the chloroplast level. Triazine-resistance had no effect on kochia germination or seedling vigor. When competing for light and nutrients, greenhouse-grown atrazine-resistant kochia accumulated 24% less dry matter than the suscetible biotypes. Under atrazine-free conditions this competitive disadvantage would slowly decrease the frequency of triazine resistance in this kochia population.
Subject Area
Agronomy
Recommended Citation
SALHOFF, CRAIG RICHARD, "VARIATION IN (KOCHIA SCOPARIA (L.) SCHRADER) GROWTH RESPONSE TO TRIAZINE HERBICIDES" (1981). ETD collection for University of Nebraska-Lincoln. AAI8208377.
https://digitalcommons.unl.edu/dissertations/AAI8208377