Abstract
Abstract: Seven imazapyr-tolerant mutant sugarcane plants, previously gener -ated by in vitro mutagenesis, were studied. The imazapyr concentrations re-quired to inhibit their acetolactate synthase (ALS basal activity) (IC 50 as μmoles acetoin h -1 mg -1 protein) were 0.77 – 5.36 times greater than that of the N12 ‘parent’. The basal ALS activities of Mut1 and Mut6 were 1.4-fold higher than that of N12. When the mutants were sprayed with Arsenal ® GEN 2 (312 and 624 g a.i. imazapyr ha -1 ), 2 months after field planting, and evaluated 9 months later, live stalk height and number were significantly lowest in Mut2, Mut3 and the control N12. No differences in sucrose, fibre and estimated yield were observed amongst lines in untreated plots. Mutant plants germinated and grew in soil treated with the herbicide (at the lethal dose of 1248 g a.i. ha -1 ). The Mut lines tested in this study offer improved options for weed control. Key words: Acetolactate synthase, ethyl methanesulfonate, imidazolinone,
Highlights
Weeds can drastically reduce cane and sugar yields (Millhollon 1992)
As in most crops, this can be achieved by conventional plant breeding, genetic transformation (Leibbrandt and Snyman 2003) and induced mutagenesis (Rutherford et al 2014)
Because of the lengthy plant breeding and selection process in sugarcane, legislative restrictions, licensing costs and public opposition to transgenesis, our preferred approach is the generation of herbicide-resistant variants of proven elite genotypes using mutagenesis
Summary
Weeds can drastically reduce cane and sugar yields (Millhollon 1992). The application of herbicides is a well-established necessity and is most crucial during plant cane establishment and subsequent ratoon crop regeneration (Campbell 2008). Herbicides must be carefully selected and applied as they disrupt essential processes (e.g. photosynthesis, amino acid biosynthesis) shared by crops and weeds. In sugarcane, this is especially difficult, as a many of the weeds are graminaceous species, e.g. Cynodon dactylon and Digitaria longifolia (Campbell 2008). Because of the lengthy plant breeding and selection process in sugarcane, legislative restrictions, licensing costs and public opposition to transgenesis, our preferred approach is the generation of herbicide-resistant variants of proven elite genotypes using mutagenesis. Cultivar N12 was selected for generating variants resistant to the herbicide imazapyr (Koch et al 2012). N12 is known to be hardy (McIntyre and Nuss 1998) and is a favored cultivar of emerging small-scale farmers in South Africa, who operate under
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