Physiological responses of sunflower Clearfield hybrids to the herbicide imazamox

Abstract

Because of the high importance of sunflower as an oilseed crop that is mainly used for human consumption, high yield and quality are very important, especially in the context of an increasing world population. Therefore appropriate and efficient cultivation of sunflower are very important for the agricultural sector. Harmful weed species appear to be the main problem for successful and sustainable cultivation of sunflower, causing considerable yield losses worldwide. Application of herbicides is the most common method for weed control in sunflower cultivation, but its biology and growth features require a continuous exploration for new and more effective tools to tackle this problem. The Clearfield production system offers the farmers a new and appropriate solution for the weed problem in sunflower by combining a herbicide resistant crop and a highly selective herbicide from the imidazolinone group. Imazamox is a highly selective herbicide, which is blocking the synthesis of branched chain amino acids in susceptible plants by inhibiting the activity of the enzyme acetohydroxyacid synthase (AHAS). Despite the high selectivity of the imidazolinines, temporal harm occasionally occurs to sunflower due to higher imazamox application rates, timing of its application as well as the environmental conditions. Although its mode of action is well known, the exact consequences of AHAS inhibition on the key physiological processes in plants, remain unclear. It is known that detoxification and degradation of the herbicide in crops plays a major role in herbicide selectivity, but these processes are still not fully understood in sunflower. In addition, there exists a lack of information concerning the possible protective effects of different groups of biostimulants on imidazolinone-treated crops, including sunflower. Concerning these ambiguities, in the current study we aimed (1) to reveal the degradation and detoxification rates and physiological effects of the herbicide imazamox in IMI-resistant and IMI-susceptible sunflower hybrids and (2) to examine the feasibility of reducing the temporal growth inhibition caused by imazamox on sunflower plants by foliar application of an amino acid extract.