RESUMEN
Meadowfoam (Limnanthes alba Hartw. ex Benth.) is an oilseed crop grown in the Willamette Valley of Oregon. Meadowfoam seed meal (MSM), a byproduct after oil extraction, contains 2-4% glucosinolate (glucolimnanthin). Activated MSM, produced by adding freshly ground myrosinase-active meadowfoam seeds to MSM, facilitates myrosinase-mediated formation of glucosinolate-derived degradation products with herbicidal activity. In the activated MSM, glucolimnanthin was converted into 3-methoxybenzyl isothiocyanate ("isothiocyanate") within 24 h and was degraded by day three. 3-Methoxyphenylacetonitrile ("nitrile") persisted for at least 6 days. Methoxyphenylacetic acid (MPAA), a previously unknown metabolite of glucolimnanthin, appeared at day three. Its identity was confirmed by LC-UV and high resolution LC-MS/MS comparisons with a standard of MPAA. Isothiocyanate inhibited lettuce germination 8.5- and 14.4-fold more effectively than MPAA and nitrile, respectively. Activated MSM inhibited lettuce germination by 58% and growth by 72% compared with the control. Results of the study suggest that MSM has potential uses as a pre-emergence bioherbicide.
Asunto(s)
Glucosinolatos/química , Glucosinolatos/farmacología , Magnoliopsida/química , Semillas/química , Biodegradación Ambiental , Bioensayo , Cromatografía Liquida , Glicósido Hidrolasas/metabolismo , Herbicidas/farmacología , Isotiocianatos/metabolismo , Espectrometría de Masas en Tándem , Tiocianatos/farmacología , Tioglucósidos/farmacologíaRESUMEN
BACKGROUND: Multiple-herbicide resistance in Lolium perenne spp. multiflorum has evolved in many areas in Oregon. To manage the resistant populations, the resistance patterns must be determined. In this study, a population (CT) suspected to be resistant to sulfometuron and hexazinone was collected from a Christmas tree plantation. RESULTS: The CT population is resistant to at least six herbicides with four different mechanisms of action: atrazine (>16-fold), diuron (2.4-fold), glyphosate (7.4-fold), hexazinone (3.1-fold), imazapyr (1.8-fold) and sulfometuron (>16-fold). Two mutations, Trp-591-Leu and Ser-264-Gly, were identified in the acetolactate synthase (ALS) and psbA gene respectively. No previously reported mutation in the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene was found. Less shikimic acid accumulated in the CT plants than in the susceptible plants after treatment with glyphosate at 0.6 kg AE ha(-1) . CONCLUSION: This study suggests that the multiple resistance patterns of Lolium perenne spp. multiflorum populations can be complex, but that chemical control options to manage these populations exist. These remaining chemical options should be integrated with non-chemical management strategies to slow the spread of multiple-resistant biotypes in agroecosystems.
Asunto(s)
Resistencia a los Herbicidas , Herbicidas/farmacología , Lolium/efectos de los fármacos , Lolium/genética , 3-Fosfoshikimato 1-Carboxiviniltransferasa/genética , 3-Fosfoshikimato 1-Carboxiviniltransferasa/metabolismo , Acetolactato Sintasa/genética , Acetolactato Sintasa/metabolismo , Regulación de la Expresión Génica , Lolium/enzimología , Datos de Secuencia Molecular , Mutación , Oregon , Complejo de Proteína del Fotosistema II/genética , Complejo de Proteína del Fotosistema II/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Análisis de Secuencia de ADN , Control de MalezasRESUMEN
BACKGROUND: Studies were conducted to elucidate the mechanism of glufosinate resistance in an Italian ryegrass population. RESULTS: Glufosinate rates required to reduce growth by 50% (GR(50)) were 0.15 and 0.18 kg AI ha(-1) for two susceptible populations C1 and C2 respectively, and 0.45 kg AI ha(-1) for the resistant population MG, resulting in a resistance index of 2.8. Ammonia accumulation after glufosinate treatment was on average 1.5 times less for the resistant population than for the susceptible populations. The glufosinate concentrations (µM) required to reduce the glutamine synthetase (GS) enzyme activity by 50% (I(50)) were 31 and 137 for C1 and C2 respectively, and 2432 for the resistant population MG. One amino acid substitution in the plastidic GS2 gene, aspartic acid for asparagine at position 171, was identified in the resistant population. CONCLUSIONS: This is the first report of glufosinate resistance in a weed species that involves an altered target site.
