Herbicide resistance-endowing ACCase gene mutations in hexaploid wild oat (Avena fatua): insights into resistance evolution in a hexaploid species

Many herbicide-resistant weed species are polyploids, but far too little about the evolution of resistance mutations in polyploids is understood. Hexaploid wild oat (Avena fatua) is a global crop weed and many populations have evolved herbicide resistance. We studied plastidic acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicide resistance in hexaploid wild oat and revealed that resistant individuals can express one, two or three different plastidic ACCase gene resistance mutations (Ile-1781-Leu, Asp-2078-Gly and Cys-2088-Arg). Using ACCase resistance mutations as molecular markers, combined with genetic, molecular and biochemical approaches, we found in individual resistant wild-oat plants that (1) up to three unlinked ACCase gene loci assort independently following Mendelian laws for disomic inheritance, (2) all three of these homoeologous ACCase genes were transcribed, with each able to carry its own mutation and (3) in a hexaploid background, each individual ACCase resistance mutation confers relatively low-level herbicide resistance, in contrast to high-level resistance conferred by the same mutations in unrelated diploid weed species of the Poaceae (grass) family. Low resistance conferred by individual ACCase resistance mutations is likely due to a dilution effect by susceptible ACCase expressed by homoeologs in hexaploid wild oat and/or differential expression of homoeologous ACCase gene copies. Thus, polyploidy in hexaploid wild oat may slow resistance evolution. Evidence of coexisting non-target-site resistance mechanisms among wild-oat populations was also revealed. In all, these results demonstrate that herbicide resistance and its evolution can be more complex in hexaploid wild oat than in unrelated diploid grass weeds. Our data provide a starting point for the daunting task of understanding resistance evolution in polyploids

Enhanced luminescence by tunable coupling of Eu3+ and Tb3+ in ZnAl2O4:Eu3+:Tb3+ phosphor synthesized by solution combustion method

[EN] ZnAl2O4:Eu3+ or Tb3+ (1 mol%) and ZnAl2O4:Eu3+/Tb3+ with varied concentrations of Eu3+ and Tb3+ were prepared by solution combustion method. The photoluminescence spectra of synthesized compounds shows that simultaneous doping of Tb3+ and Eu3+ causes enhancement in Eu3+ luminescence intensity. This indicates some energy transfer from Tb3+ to Eu3+. This phenomenon of Tb3+ -> Eu3+ energy transfer, accomplishing enhanced intensity of Eu3+ ions, is attributed to the cross relaxation phenomenon, which is favored by overlap between the donor and acceptor transition. The energy is transferred to Eu3+ cascade rapidly via non-radiative transitions to D-5(0) state. The synthesized compounds were characterized by XRD, SEM for their structural and morphological characteristics respectively.This work was supported by the European Commission through NanoCIS project (FP7-PEOPLE-2010-IRSES ref. 269279).Verma, N.; Marí, B.; Singh, KC.; Jindal, J.; Yadav, S.; Mittal, A. (2019). 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