Eleusine, herbicide resistance

Zeng, L. and Baird, W. V. (1997). Genetic basis of dinitroaniline herbicide resistance in a highly resistant biotype of goosegrass (Eleusine indica). J. Hered. 88, 427-432. 

Anthony, R. G. and Hussey, P. J. (1999). Double mutation in Eleusine indica alpha-tubulin increases the resistance of transgenic maize calli to dinitroaniline and phosphorothioamidate herbicides. Plant ]. 18, 669-674. 

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). 

The occurrence of dinitroaniline-resistance in Eleusine is quite alarming, because it is one of the world s ten worst weeds (4) and dinitroaniline herbicides are a cost-effective way of controlling this weed in cotton. Even more alarming... 

Crop plants in which dinitroaniline herbicides are used are tolerant of the herbicide by a number of mechanisms. Some researchers have turned their attention to these in the hope of finding a mechanism for dinitroaniline resistance in Eleusine. 

Lipids. Dinitroaniline herbicides are effective on small-seeded, lipid-poor species. Hilton and Christiansen (7) examined the level of seed lipid and the susceptibility of a plant to trifluralin and found a good correlation between the two. These authors concluded that the herbicides would be compartmentalized into the lipid bodies of the seed and away from the growing tip of the plant. Upadhyaya and Nooden (8) even found that there is a differential between susceptible and tolerant species in the uptake of oryzalin into the membrane system, indicating that more than the seed lipids may be involved in determining dinitroaniline sensitivity. Chernicky (9) investigated the possibilities that alterations in the amount of lipid is involved in the resistance of Eleusine to dinitroaniline herbicides. Both susceptible (S) and resistant (R) biotypes had less total lipid than tolerant crop species and even most sensitive weed species. The S biotype had actually 36% more total lipid in the roots than the R biotype (a result opposite to what one would expect if higher lipid content correlates dinitroaniline resistance). 

Because dinitroaniline herbicides are one of the most effective methods of weed control in cotton, the development of resistance to dinitroaniline herbicides in Eleusine was especially serious. Moreover, many of the herbicides that are effective on the R Eleusine [see Mudge t al. (3)] are much more costly or more detrimental to the growth of the cotton than the dinitroaniline herbicides. In an attempt to find a solution to this problem, Figliola st al- (22) isolated two pathogenic fungi,... 

These studies established that (a) the microtubules of the R biotype are hyperstabilized and (b) phenocopies of the R biotype in structure and in insensitivity to microtubule disrupters could be induced by treating the S biotype with taxol. From this, one could conclude that a major factor in dinitroaniline-resistance in Eleusine is the hyperstability, presumably caused by the novel 0-tubulin form in the R biotype. This does not eliminate the possibility that the binding of dinitroaniline herbicides is altered in the R biotype and we hope to investigate this possibility as well. 

The frequent use of AOPP and CHD graminicides has resulted in the development of resistance to these herbicides in some grass species throughout the world [33]. Up to now, 35 resistant species [34] have been reported. The species in which resistance has developed include the important grass weeds Alopecurus myosuroides, Avena fatua, Setaria viridis, S. faheri, Lolium rigidum and Eleusine indica. 

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