Lactuca, herbicide resistance

Mallory-Smith, C.A. (1990). Identification and inheritance of sulfonylurea herbicide resistance in prickly lettuce (Lactuca serriola). Ph.D. dissertation. University of Idaho, Moscow, ID, p. 58. 

Mallory-Smith, C.A., D.C. Thill, M.J. Dial, and R.S. Zemetra (1990b). Inheritance of sulfonylurea herbicide resistance in Lactuca spp. 

Resistant biotypes being reported in the early 1990s were selected by chlorsul-furon or metsulfuron-methyl in wheat-growing areas or by sulfometuron-methyl in non-crop areas. While resistance of Lolium rigidum to ALS-inhibitors was attributed to enhanced herbicide metabolism [50] it was shown, for Lolium perenne and dicotyledonous species like Stellaria media, Kochia scoparia, Scdsola iberica and Lactuca serriola, that resistant biotypes had a mutated ALS with reduced susceptibility to ALS-inhibitmg herbicides [51-53]. The IC50S for sulfonylureas, which were determined in vitro with ALS isolated from Stellaria media, Salsola iberica and Lolium perenne, increased 4- to 50-fold in the resistant biotypes. Smaller increases, about 2- to 7-fold, were determined in the same biotypes for the imidazo-linone herbicide imazapyr [53]. 

On the other hand, the ALS of Lactuca setriola possessing a mutation of proline at 171 to histidine has been shown to be resistant to the SU and to exhibit cross-resistance to the IM but not to the PC. The ALS of K. scoparia possessing a mutation of proline at position 171 to serine was inhibited by the PC herbicide, bispyribac-sodium (BS) as potently as the wild-type enzyme but expressed a cross-resistance to the PC herbicide, pyrithiobac-sodium (Fig. 4) (5). 

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