Abstract
Redroot pigweed (Amaranthus retroflexus) and prostrate pigweed (A. blitoides)
populations resistant to several sulfonylurea herbicides were collected from a young for estnear Ganot junction (coastal plain) in Israel. The forest has been treated every autumn since1988, with a mixture of sulfometuron (0.07 kg/ha) and simazine (1.75 kg/ha). Two resistantred root pigweed (R) populations, GR1 and GR2, were collected from two different locations at Ganot junction; one sensitive population ($3) was collected in 1991 at Mishmar haShiv'a (a farm near Ganot junction), and another (S5) was collected at Nov (Golan Heights). Theresistant prostrate pigweed populations (GRll and GR13) were collected from the treatedjunction during the summer of 1991, and the sensitive one ($24) was collected at MazkeretBatya (1986). The response of these populations to various herbicides applied pre-emergenceand early postemergence (2--4-leaf stage) was assayed, and a root elongation bioassay insquare petri dishes was conducted. The EDs0 (herbicide dose causing 50% inhibition ofgrowth) was calculated for each herbicide/population combination. With chlorsulfuron and sulfometuron applied pre-emergence, the EDs0 values of the resistant pigweed populations were 40 times higher than those of the sensitive populations. When root elongation in res-ponse to these herbicides was compared, the resistance ratio (EDsoR/EDsoS) was almost 100.The resistant pigweeds exhibited a clear cross-resistance to imidazolinone herbicides such as imazapyr, which is also known to inhibit the AHAS enzyme. The resistant populations of prostrate pigweed, but not those of redroot pigweed, were found to be also triazine-resistant. These data indicate that the two phenomena have developed independently.Furthermore, they show that combining herbicides of different modes of action is not always sufficient to prevent the evolution of herbicide resistance. No differences were observed between R and S populations of the two pigweeds in response to pyridate and bromoxynil applied postemergenee. Studies of the resistance mechanism to sulfonylureas in Amaranthus spp. are now in progress.
populations resistant to several sulfonylurea herbicides were collected from a young for estnear Ganot junction (coastal plain) in Israel. The forest has been treated every autumn since1988, with a mixture of sulfometuron (0.07 kg/ha) and simazine (1.75 kg/ha). Two resistantred root pigweed (R) populations, GR1 and GR2, were collected from two different locations at Ganot junction; one sensitive population ($3) was collected in 1991 at Mishmar haShiv'a (a farm near Ganot junction), and another (S5) was collected at Nov (Golan Heights). Theresistant prostrate pigweed populations (GRll and GR13) were collected from the treatedjunction during the summer of 1991, and the sensitive one ($24) was collected at MazkeretBatya (1986). The response of these populations to various herbicides applied pre-emergenceand early postemergence (2--4-leaf stage) was assayed, and a root elongation bioassay insquare petri dishes was conducted. The EDs0 (herbicide dose causing 50% inhibition ofgrowth) was calculated for each herbicide/population combination. With chlorsulfuron and sulfometuron applied pre-emergence, the EDs0 values of the resistant pigweed populations were 40 times higher than those of the sensitive populations. When root elongation in res-ponse to these herbicides was compared, the resistance ratio (EDsoR/EDsoS) was almost 100.The resistant pigweeds exhibited a clear cross-resistance to imidazolinone herbicides such as imazapyr, which is also known to inhibit the AHAS enzyme. The resistant populations of prostrate pigweed, but not those of redroot pigweed, were found to be also triazine-resistant. These data indicate that the two phenomena have developed independently.Furthermore, they show that combining herbicides of different modes of action is not always sufficient to prevent the evolution of herbicide resistance. No differences were observed between R and S populations of the two pigweeds in response to pyridate and bromoxynil applied postemergenee. Studies of the resistance mechanism to sulfonylureas in Amaranthus spp. are now in progress.
| Original language | American English |
|---|---|
| Pages (from-to) | 335 |
| Journal | Phytoparasitica |
| Volume | 20 |
| State | Published - 20 Jan 1992 |