Abstract
Weeds represent an increasing challenge for crop systems since they have evolved adaptability to adverse environmental conditions, such as salinity stress. Herbicide effectiveness can be altered by the quality of water in which the weed is growing. This research aimed to study the combined effect of salt stress and recurrent selection with a sublethal dose of imidazolinone herbicides in the shifting of the sensitivity of Echinochloa colona (L.) Link (junglerice) to imidazolinone herbicides. This study was divided into two experiments; in experiment I, three recurrent selection cycles were conducted in Pelotas/RS/Brazil with imazapic + imazapyr at 0.125× the field rate; and in experiment II, three recurrent selection cycles were conducted in Fayetteville/AR/USA with imazethapyr, at 0.125× the recommended dose. Salt stress was implemented by irrigation with 120 mM sodium chloride (NaCl) solution. The effective dose for 50% control of the population (ED50) values increased from the field population to the second generation (G2) after recurrent selection with a sublethal dose of imidazolinone combined with salt stress, supporting the hypothesis of reduced susceptibility by the combination of these abiotic factors. Recurrent exposure to a sublethal dose of imazapic + imazapyr or imazethapyr, combined with salt stress, reduced susceptibility of Echinochloa colona (L.) plants to imidazolinone herbicides.
Highlights
Population projections indicate rapid and continued global growth in the coming decades, exceeding 9.5 billion people in 2050, increasing demand for food in quantity and quality [1]
ED50 values were 37.25, 43.03, and 53.38 g·ai·ha−1 G0, G1, and G2, respectively, after three cycles of recurrent selection. These results demonstrate that sensitivity to imidazolinone herbicides reduced as the generations evolved through recurrent selection with a sublethal dose of imidazolinone herbicides under salt stress, supporting the hypothesis that E. colona can gradually adapt to this combination of abiotic stress factors (Figure 3)
This study shows that the recurrent selection of E. colona with a sublethal dose of imazapic + imazapyr or imazethapyr combined with salt stress increases plant tolerance to these stress factors with transgenerational effect, resulting in reduced susceptibility to
Summary
Population projections indicate rapid and continued global growth in the coming decades, exceeding 9.5 billion people in 2050, increasing demand for food in quantity and quality [1]. Weeds are one of the main problems causing damage and reduced rice yields worldwide, especially the weedy rice and Echinochloa species [3,4,5]. Selective grass control in rice became possible with the introduction of the ClearfieldTM production system, starting in the early-2000s, with cultivars resistant to herbicides in the imidazolinone chemical group (e.g., imazamox, imazethapyr, imazapic, imazapyr) [6]. Grass weeds such as weedy rice, barnyardgrass, and junglerice quickly evolved resistance to these herbicides, reducing grain yield and creating socioeconomic problems [7,8,9].
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