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Weed biotypes

Pfister, K. and C.J. Amtzen (1979). The mode of action of photosystem II-specific inhibitors in herbicide-resistant weed biotypes. Z. Naturforsch. Sect. C Biosci., 34 996-1009. [Pg.109]

In other weed biotypes, resistance to triazine herbicides is likely conferred by rapid metabolism of the herbicides to inactive compounds. A chlorotoluron-resistant biotype of blackgrass (slender foxtail) was cross-resistant to various other groups of herbicides, including triazines (Kemp et al., 1990). The mechanism of chlorotoluron resistance was Cyt P450-based enhanced oxidative metabolism through /V-demethylation and ring-methyl hydroxylation (Moss and Cussans, 1991). Consequently, it is likely that resistance to triazines in this blackgrass biotype is also due to enhanced herbicide detoxification. [Pg.116]

In summary, triazine resistance in weeds is most commonly due to a target site alteration that confers a very high level of resistance to. y-triazinc herbicides. Although a Ser264 to Gly mutation in the D1 protein is most common, additional alterations have been identified that confer resistance to triazines and other classes of PS II inhibitors. Enhanced herbicide metabolism plays a major role in conferring resistance in only a few weed biotypes. In these biotypes, the pattern of resistance may be broader, with some cross-resistance to av-trazinones, uracils, heterocyclic ureas and phenyl ureas. The level and pattern of resistance to various herbicides in these biotypes depend, presumably, on the activity and specificity of the enzyme(s) responsible for the enhanced herbicide metabolism. [Pg.116]

Within North America and a few other countries, most triazine-resistant weed biotypes have been reported after repeated use of atrazine in com and sorghum. In some areas of Western Europe and other countries, triazine-resistant weeds have been reported after repeated use of simazine in orchards and along roadsides. A few triazine-resistant weeds (e.g., kochia, cheatgrass, and common groundsel) have biotypes with triazine resistance in nurseries and perennial tree crops, as well as along railways and roadsides. [Pg.122]

Excellent progress has been made in the understanding of the cause, nature, genetics, mechanism and solutions of herbicide-resistant weeds since the first triazine-resistant common groundsel was reported more than 35 years ago. Resistance management programs have been extremely successful in controlling most weeds that have developed resistance to the triazine herbicides. However, research is critical to better understand the rapid increase and spread of many new weed biotypes resistant to several classes of herbicides. [Pg.128]

Clay, D.V. and C. Underwood (1989). The identification of triazine- and paraquat-resistant weed biotypes and their response to other herbicides. In Cavalloro, R., and Noye, G., eds, Proc. E. C. Experts, Grays, Tollose, Denmark, November 15-17, 1988. Luxembourg Office for Official Publications of the European Communities, pp. 47-55. [Pg.129]

Lopez-Garcia, M.C., C. Zaragoza, and R. DePrado (1996). Survey and agronomic importance of atrazine resistant weed biotypes in Argon, (Spain). In R. Deprado, J. Jorrin, L. Garcia Torres, and G. Marshall, eds., International Symposium on Weed and Crop Resistance to Herbicides. April 3-6, 1995. Cordoba, Spain Graficas TYPO, S.L, pp. 251-252. [Pg.131]

Biotypes of weed species are resistant to virtually all classes of herbicides previously used for their control. Most weeds resistant to triazine herbicides have appeared after the triazines alone were used for 8-10 years of consecutive treatments, sometimes much longer (Eleftherohorinos et al., 2000 Gressel, 2002). Weed biotypes resistant to the ALS inhibitors have often been reported after only 3 to 5 years of repeated use, and in some cases after only 1 or 2 years (Kendig and Barrentine, 1995 Jeffers et al., 1996 Lovell et al., 1996b Sprague et al., 1997a Hall et al., 1998). [Pg.134]

Table 11.2 Occurrence of resistant weed biotypes to different herbicide groups up to 2006... Table 11.2 Occurrence of resistant weed biotypes to different herbicide groups up to 2006...
Table 11.3 The number of herbicide-resistant weed biotypes in each of 52 countries in 2006... Table 11.3 The number of herbicide-resistant weed biotypes in each of 52 countries in 2006...
Although the ALS inhibitor herbicides have been used for approximately 20 years, the number of resistant weed biotypes for this group now exceeds those for all other types of herbicides. Singh and Shaner (1995) and Boutsalis (2001) reported that a total of five chemical families or herbicide classes are commercially marketed as inhibitors of ALS, and that these herbicides comprise more than 50 active ingredients for selective use in many different crops. They include sulfonylureas, imidazolinones, triazolopyrimidines, sulfonylamino-carbonyl-triazolinones, and pyrimidinyl (thio)benzoates. [Pg.136]

Christopher et al. (1992) reported that a chlorsulfuron-resistant rigid ryegrass in Australia was resistant to most other sulfonylurea and imidazolinone ALS inhibitors. However, a common cocklebur biotype resistant to several imida-zolinone herbicides was not resistant to sulfonylurea herbicides (Saari et al., 1994). It is, therefore, difficult to generalize as to patterns of resistance within the five classes of ALS inhibitors. Weed biotypes resistant to one herbicide will usually show some level of resistance to most herbicides within the same class, and may in addition show some resistance to ALS inhibitors in other classes. [Pg.140]

Multiple-resistance mechanisms, defined as resistance due to more than one mode of action or class of herbicide, have been reported in several ALS-resistant weed biotypes - including false cleavers, wild oat, common waterhemp, kochia, rigid ryegrass in Australia (Powles and Matthews, 1992 Preston and Mallory-Smith, 2001), and wild radish (Walsh etal, 2004a). [Pg.142]

In certain situations it is possible to overcome herbicide metabolism-based resistance by adding an ingredient that will block detoxification of the herbicide in the resistant weed. One example is with propanil-resistant Echinochloa colona in rice in Latin America. The addition of piperophos, an organophosphate insecticide that inhibits the aryl acylamidase activity that confers resistance on the weed biotype [11]. This combination, based on an undo standing of the resistance mechanism, has beat approved for use on resistant... [Pg.160]

TABLE V. Occurrence and Distribution of Weed Biotypes Resistant to Various Nontriazine Herbicides... [Pg.342]

The dinitroaniline herbicides, trifluralin and pendimethalin, have been utilized in greater than 80% of the cotton acreage in the Southern United States because of their very effective weed control in this crop (1). Many of these fields are essentially in cotton monoculture and hence the continued use of these herbicides has constantly selected out those weeds most tolerant of these herbicides. Under such a selection pressure, the appearance of weed biotypes resistant to dinitroaniline herbicides is expected (2). The first report of a resistant biotype did not appear until 1984, Mudge si gl. (3) described the occurrence of dinitroaniline-resistance in Eleusine indica in counties in South Carolina where cotton is extensively cultivated. Since that initial report, dinitroaniline-resistant Eleusine has been detected throughout the midsouth (H. LeBaron, personal communication). [Pg.364]

Table I. Herbicides or Classes of Herbicides With Resistant Weed Biotypes and the Known or Suspected Mechanism of Resistance... Table I. Herbicides or Classes of Herbicides With Resistant Weed Biotypes and the Known or Suspected Mechanism of Resistance...
Many of the characteristics which combine to make ALS an excellent target for engineering beneficial herbicide resistance in crop plants may also lead to the proliferation of herbicide-resistant weeds. These characteristics include the following sulfonylurea herbicide resistance is a semi-dominant trait that is carried on a nuclear gene(s) ALS is the single primary site of action there are multiple positions in ALS that can be mutated to confer herbicide resistance mutant ALS enzymes can possess full catalytic activity. The latter property results in engineered crop plants that are fit, but can equally well result in weed biotypes that are fit. [Pg.468]

Since a number of triazine tolerant weed biotypes have been discovered through triazine application to crop lands, development of... [Pg.109]


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