311 GENETIC AND MOLECULAR STUDIES OF DINITROANILINE HERBICIDE-RESISTANT GOOSEGRASS [Eleusine indica (L.) Gaertn.

Abstract

Goosegrass (Poaceae) is a member of a small but economically important genus, containing approximately 10 species. Goosegrass is a noxious weed in cotton, soybean and turf production, but was effectively controlled by the application of dinitroaniline herbicides (DNH). However, in the early 1970's two DNH tolerant biotypes were discovered. The highly resistant (R-) biotype is now found in many areas in the southeastern US, while the intermediately resistant (I-) biotype is known only from SC. We have investigated the inheritance and expression of resistance, using radicle/root growth bioassays, in F2 progeny derived from F1 hybrids (created by outcrossing this autogamous weed). The hybrid nature of presumptive F1 seedlings was confirmed by isoenzyme analysis. The DNH's effect their herbicidal action by disrupting the assembly of tubulin dimers into microtubules (MTs). The R-biotype has been shown to possess MTs that are hyperstable in the presence of the herbicide. Mutation(s) in a tubulin protein would be manifested in the gene and might be detectable at the nucleic acid level. We found that the alpha-, beta- and gamma-tubulins are encoded by multigene families (∼ 5.7 and 8 members, respectively). DNA polymorphisms were detected, but were not strictly correlated with biotype. Therefore, the differences in herbicide response phenotype cannot be attributed to large deletions and/or insertions in a tubulin gene(s).