EPSPS

This paper reviews the literature to understand the effects of glyphosate resistance on plant fitness at the molecular, biochemical and physiological levels. A number of correlations between enzyme characteristics and glyphosate resistance imply the existence of a plant fitness cost associated with resistance-conferring mutations in the glyphosate target enzyme, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). These biochemical changes result in a tradeoff between the glyphosate resistance of the EPSPS enzyme and its catalytic activity.

Earlier papers by Gaines et al 2012 Weed Technology and Goh et al 2016 Pest Management Science, documented a glyphosate resistance Echinochloa population from the irrigated north-west Ord River irrigation region of Western Australia. AHRI PhD student Sou Sheng Goh studied this population for his PhD research. Among other studies, Goh completed excellent work to identify the mechanistic basis of glyphosate resistance in this Echinochloa population. Goh examined for but did not find EPSPS resistance gene mutations and/or EPSPS gene amplification. Thus Goh established that glyphosate resistance in this particular resistant biotype is NON-target site based. 

This study confirms and characterises glyphosate resistance in two polyploid Echinochloa colona populations from north-eastern Australia.

Glyphosate is the most important and widely used herbicide in world agriculture. Intensive glyphosate selection has resulted in the widespread evolution of glyphosate-resistant weed populations, threatening the sustainability of this valuable once-in-acentury agrochemical. Field-evolved glyphosate resistance due to known resistance mechanisms is generally low to modest.

Weed populations can have high genetic plasticity and rapid responses to environmental selection pressures. For example, 100-fold amplification of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene evolved in the weed species Amaranthus palmeri to confer resistance to glyphosate, the world’s most important herbicide.

In a world of more than 6 billion people, humans heavily rely on the dependable cultivation of the global food grain crops: rice, wheat, soybeans, maize (and cotton for fiber). History shows that threats to food production have major repercussions, including famine, war, and civil unrest.