GM plants and resistance – resistance-management

Journal or Publishing Institution: GMO Round-table Leaflets

Study: https://web.archive.org/web/20180914160701/http://bdarvas.hu/download/pdf/GenetE.pdf

Author(s): Darvas, B.

Article Type: Report

Record ID: 558

Abstract: Ninety % of first generation GM plants evaluated in EU serve plant protection purpose. Twenty % are “insect”-resistant (Bt), 30% are “herbicide”- tolerant (glyphosate) and the further 40% are the combination of the mentioned two types. Pesticide resistance for an active ingredient used in a longer period is developed sooner or later in treated pest communities. The 10th generation of Plodia interpunctella was tolerant for MON 810 grinded leaf which suggest a quick expiration time for this GM hybrid. Larvae resistant for MON 810 maize showed tolerance for DIPEL. In case of Plutella xylostella, four Cry-receptors were separated. Larvae of Cry1C-resistant P. xylostella showed strong cross-resistance on CrylAb, CrylAc and Cry1F toxins. Middle or low cross-resistance was demonstrated on Cry1Aa and Cry9C toxins. In cases of Cry1Bb, CrylJa and Cry2A toxins cross-resistance did not appear. Cross-resistance may develop in case of toxin with two different binding sites by way different mechanisms in background of resistance. Owners of GM plants suggest a 20–50% isogenic showing rate which conserve the Cry toxin sensitive pest population as a management of Cry1 resistance. This method means pest breeding in a significant sized field. In next rows 5–30% intraspecific hybrid seeds were measured with pollen competition. Resistance management in case of cob pests (Helicoverpa armigera) is problematic because of variable Cry toxin contents of seeds in different position. Thus strong selection pressure with sublethal concentration resulted in larval survivors and generated Cry1A-resistant pest populations. As a solution maize varieties with different flowering time as GM variety may be advised. A further problem in the present “Cry1-resistance management” that the developing times of larvae and swarming of imagos may significantly different consuming Bt-plant or its near isogenic line. This decrease the chance of meeting the Cry toxin sensitive and resistant populations. In case of GM varieties producing variable Cry toxins, the Cry toxin amount was produced in a hectare – which is presently critical too – higher onward. Glyphosate active ingredient as a total herbicide was introduced in the market at 1970. Well known that some weeds originally tolerate glyphosate, for example Abutilon theophrasti, Chenopodium album and Xanthium stumarium. There are two strategies for glyphosate tolerance. Glyphosate binding site was change to less sensitive type or plants produce extra detoxifying enzymes which metabolize glyphosate into its less phytotoxic metabolites. The glyphosate-tolerant GM plant made possible the post emergent glyphosate usage, thus glyphosate utilization may be expanded. Glyphosate-tolerant Amaranthus spp., Ambrosia artemisifolia, Conyza canadensis, Eleusine indica, Lolium multiflorum, Plantago lanceolata, Plantago major, Sorghum halepense populations have described until now. The glyphosate-tolerance may be 8–15 times more as in case of a sensitive weed population. In a longer glyphosate usage may result 10–50% populations of a species belong to glyphosate-tolerant group. This participate in that phenomenon while herbicide usage slightly decrease during the first 3–5 years after GM plant appearance, but later when resistant weed populations selected herbicide usage start to increase again. There are no examinations on this field in Hungary.

Keywords: Cry1-resistance; MON 810; Dipel; Cry receptor; cross-resistance; resistancemanagement; glyphosate; glyphosate-tolerant weeds; Eleusine indica; Conyza canadensis; Plantago major; Plantago lanceolata; Lolium multiflorum; Ambrosia artemisifolia; Sorghum halepense

Citation: Darvas, B., 2009. GM plants and resistance – resistance-management. GMO Round-table Leaflets, 22, 11.