Structural and Biochemical Characterization of Dinitroaniline-Resistant Eleusine

Dinitroaniline-resistant goosegrass ( Eleusine indica ) biotypes were first discovered in South Carolina and have now been found in several southern states where trifluralin is used for weed control in cotton. Two kinds of resistant biotypes have been noted: one is highly-resistant (R) and is unaffected even by saturated solutions of dinitroaniline herbicide, whereas an intermediate-resistant (I) biotype is only 50X resistant to trifluralin and less than 10X resistant to oryzalin compared with the susceptible (S) biotype. Both R and I biotypes are cross-resistant to phosphoric amide herbicides. Tubulin from the R is able to polymerize into microtubules even in the presence of oryzalin, whereas that of the S biotypes cannot. Western blots of tubulin from the R biotype reveal two β-tubulin isotypes whereas only one form is noted in the S biotype. Because the R biotype is hypersensitive to the microtubule-stabilizing agent taxol, it is likely that the R biotype is resistant by having hyperstabilized microtubules. The I biotype has no gross alteration in tubulin nor extreme sensitivity to taxol, indicating that this biotype has a different resistance mechanism than the R.