Negative cross resistance

Table 8.1 Positive and negative cross-resistance of PS II herbicides in a selection of mutants of various organisms...

Yerkes et al. (1996) reported that although chlorophyll fluorescence measurements and C02 assimilation in resistant jimsonweed leaves were affected within 1 day of atrazine application, they returned to normal (at rates and levels equivalent to those in untreated leaves) within 5 days. Atrazine-resistant jimsonweed was cross-resistant to simazine, but was susceptible to prometryn, metribuzin, terbacil, and other herbicides. Chlorophyll fluorescence was unaffected in triazine-resistant pigweed, which showed cross-resistance to some triazines, moderate resistance to metribuzin and terbacil, and negative cross-resistance to bentazon and pyridate. 

The term negative cross-resistance is used when a herbicide-resistant biotype is more sensitive to and more easily controlled by classes of herbicides other than the class to which it is resistant. 

It is noteworthy that negative cross-resistance has been reported in some cases. Negative cross-resistance refers to a situation in which increasing resistance to one insecticide in an insect population confers an increasing susceptibility to another. The best example of... 

Villatte, F., Auge, D., Touton, P, Delorme, R., and Fournier, D., Negative cross-resistance in insecticide-resistant cotton aphid Aphis gossypii Glover, Pestic. Biochem. Physiol., 65,55,1999. 

Search for systemic compounds with low inherent risk or negative cross-resistance including biorational approaches... 

The negative cross-resistances in atrazine-resistant weeds include herbicides that act at or near the same site in photosystem II (DNOC and dinoseb) as well as herbicides acting on other photosystems (paraquat) or at totally different sites. There was negative cross-resistance to other tubulin binding herbicides in dinitroaniline resistant Eleucine indica (Table II), but not to six commercial herbicides on this weed (12). The negative cross-resistance to imazaquin (Table II) occurred in only one of 21 chlorsulfuron resistant mutants. The other mutants had varying levels of co-resistance to imazaquin. 

Table II. Negative Cross-Resistance of Herbicide Resistant Biotypes...

Primary resistance species Negative cross- resistance parameter measured Iso R/S ref... 

As already stressed, the mutation Set264 Gly is one which has been observed in nature. It is found by now in all countries and in a variety of weeds which are rendered resistant t ainst triazines and triazinones (see Table 1). It should be noted, that atrazine-resistant rape with a modified Dl protein (Ser264 Gly) is used as a crop in Canada. Resistance against ureas is comparably small and against phenolic herbicides like i-dinoseb, ioxynil and DNOC negative cross resistance is observed. 

The use of fungicides exhibiting negative cross resistance is theoretically a suitable way to decrease the frequency of resistant isolates. Unfortunately, negative cross resistance is very rare in fungicide resistance. 

B2 10 -Tubuline assembly in mitosis N-Phenyl- carbamates Diethofencarb Negative cross resistance to B1... 

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