Abstract
A population of Amaranthus tuberculatus (var. rudis) evolved resistance to 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor herbicides (mesotrione, tembotrione, and topramezone) in Nebraska. The level of resistance was the highest to mesotrione, and the mechanism of resistance in this population is metabolism-based likely via cytochrome P450 enzymes. The increasing number of weeds resistant to herbicides warrants studies on the ecology and evolutionary factors contributing for resistance evolution, including inheritance of resistance traits. In this study, we investigated the genetic control of mesotrione resistance in an A. tuberculatus population from Nebraska, USA. Results showed that reciprocal crosses in the F1 families exhibited nuclear inheritance, which allows pollen movement carrying herbicide resistance alleles. The mode of inheritance varied from incomplete recessive to incomplete dominance depending upon the F1 family. Observed segregation patterns for the majority of the F2 and back-cross susceptible (BC/S) families did not fit to a single major gene model. Therefore, multiple genes are likely to confer metabolism-based mesotrione resistance in this A. tuberculatus population from Nebraska. The results of this study aid to understand the genetics and inheritance of a non-target-site based mesotrione resistant A. tuberculatus population from Nebraska, USA.
Highlights
Waterhemp [Amaranthus tuberculatus] is a classic example of herbicide resistance evolution
The F1 families showed a lack of dominance or recessivity (Table 3), and the degree of dominance in F1 families varied from additive (SR/F1-5), incomplete recessive (SR/F1-9), and incomplete dominance (SR/F1-13; Table 3)
The closest to complete dominance was SR/F1-13, which was the only F1 family for which the R parent was previously crossed under greenhouse conditions (R × R)
Summary
Waterhemp [Amaranthus tuberculatus (var. rudis)] is a classic example of herbicide resistance evolution. A. tuberculatus is a native species of the Midwestern United States, and it has become a predominant weed in corn-soybean cropping systems (Owen, 2008; Waselkov and Olsen, 2014). The biology of A. tuberculatus is an important factor contributing to its adaptation in row-crop production systems. A single A. tuberculatus female plant can produce over a million seeds depending on density (Hartzler et al, 2004); herbicide resistance may evolve and spread faster in A. tuberculatus than other monoecious weedy Amaranthus. A. tuberculatus is ranked among the Inheritance of Mesotrione Resistance worst herbicide resistant weeds (Tranel et al, 2011; Heap, 2014). As of 2017, populations of A. tuberculatus have evolved resistance to six herbicide sites-of-action (SOA) in the United States (Heap, 2017)
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