Recurrent Selection with Low Herbicide Rates and Salt Stress Decrease Sensitivity of Echinochloa colona to Imidazolinone

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.

Herbicide Physiology and Environmental Fate

“…Andreasen et al [3] explored how the foliar and soil application of flufenacet and prosulfocarb affected Italian ryegrass (Lolium multiflorum L.) control. Benedetti et al [4] examined recurrent selection with low herbicide rates and salt stress, which resulted in Echinochloa colona's reduced sensitivity to imidazolinone herbicides. Similarly, Fipke et al [5] studied the transgenerational effect of drought stress and sub-lethal doses of quizalofop-P-ethyl, resulting in decreasing sensitivity to herbicide and biochemical adjustments in Eragrostis plana.…”