Identification and documentation of herbicide resistance

Abstract

Les programmes proactifs de gestion de la résistance aux herbicides sont basés sur la détection rapide des populations résistantes et sur la connaissance des combinaisons de mauvaises herbes et d'herbicides prédisposées au développement de cette résistance. Les mauvaises herbes annuelles, prolifiques productrices de graines, génétiquement variées et exposées de façon répétée à des herbicides du même mode d'action, sont sujettes au développement rapide de la résistance. Quand la résistance est soupçonnée, des échantillons de graines sont recueillis et évalués par un bioessai du plant entier. Ces bioessais sont conduits en champ, en chambre de croissance ou en plats de Pétri. Des courbes complètes de réponse aux doses sont tracées en utilisant une population sensible aux herbicides et une population soupçonnée de résistance. Le bioessai conduit en chambre de croissance est la méthode la plus fiable d'identification de nouveaux cas de résistance aux herbicides. Les bioessais basés sur la détection biochimique d'un seul mécanisme de résistance ne sont pas fiables pour la détection de nouveaux cas de résistance.Proactive herbicide resistance management programs rely upon early detection of resistant populations and knowledge of which combinations of weed and herbicide are prone to the development of resistance. Annual weeds that are prolific seed producers, genetically diverse, and repeatedly exposed to a single herbicide mode of action, are prone to rapid development of resistance. When resistance is suspected, seed samples are collected and evaluated using a whole plant bioassay. Whole plant bioassays are conducted underfield, growth room, or Petri dish conditions. Complete dose response curves for the suspected resistant and a reference susceptible population are used to verify resistance. Bioassay, conducted in growth rooms, is the most reliable method for identification of new cases of herbicide resistance. Bioassays, based on the biochemical detection of a single mechanism of resistance, are not reliable for screening for new occurrences of resistance

Resistance of Raphanus raphanistrum to the herbicide metsulfuron-methyl

“…According to Heap (1994), the DL 50 or GR50 is the dose required to achieve 50% control or to reduce plant DM by 50% compared to untreated plants of resistant and susceptible biotypes. From the curves generated, one can calculate the value of DL 50 or GR 50 in g i.a.…”

“…In Brazil, the first case of resistance to ALS inhibitors, involving the genus Raphanus, was with Raphanus sativus, documented in 2001 (Heap, 2013). In the south of the country, the selection pressure caused by repetitive use of ALS inhibitors in controlling R. sativus selected biotypes resistant to active ingredients such as: chlorimuron ethyl, cloransulam methyl, imazethapyr, metsulfuron-methyl and nicosulfuron (Theisen, 2008).…”

“…The first report of weed resistance in Brazil has been with the species Bidens pilosa, resistant to ALS-inhibiting herbicides, in 1993 (Heap, 2013). ALS-inhibiting herbicides are widely used due to low toxicity in mammals, wide crop selectivity and high efficacy at low doses (Yu et al, 2012).…”

“…In Brazil, there is currently documented the resistance of 31 weed species with different action mechanisms, with 14 species resistant to ALS-inhibiting herbicides (Heap, 2013).…”

Protocols for Robust Herbicide Resistance Testing in Different Weed Species

“…Different approaches have been developed according to the aims, required level of accuracy, time and resources available, as well as the weed species considered [6][7][8][9][10][11][12] . However, when confirmation of the resistance status of a new weed biotype is required (i.e., a group of individuals that share several physiological characteristics, including the ability to survive one or more herbicides belonging to a particular group used at a dose that would normally control them), a robust whole plant bioassay needs to be performed in a controlled environment 4,11 .…”