Tolerance and the Basis for Selectivity to 2,4-D in PerennialGlycineSpecies

Abstract

Twenty accessions within 11 perennialGlycinespecies plus soybean were tested for tolerance to 2,4-D. Soybean was severely injured by 2,4-D, but 13 of theGlycineaccessions had 15% or less injury 4 weeks after 2,4-D application. Greatest 2,4-D tolerance occurred with accessions ofG. latifoliaandG. microphylla.There was no difference among tolerant accessions ofG. latifoliaandG. microphyllaand susceptible accessions ofG. canescensin recovery or absorption of14C-2,4-D 1, 3, 7, or 14 days after treatment (DAT). Distribution of14C from14C-2,4-D in various plant parts was similar among accessions. Metabolism of 2,4-D in the tolerant accessions (81 to 89% 1 DAT) was higher and more rapid than in susceptible accessions (approximately 50%, 1 DAT). The same five metabolites plus parent 2,4-D were extracted from the treated leaf of all accessions at all sampling dates. However, relative distribution between metabolites differed between tolerant and susceptible accessions. More rapid metabolism of 2,4-D in treated leaves of tolerantGlycineaccessions can explain differential 2,4-D responses.