Cleancrop™ Brassica System: The development of herbicide resistant brassica crops for New Zealand farming systems

Abstract

This paper presents results from a breeding program which, using seed mutagenesis combined with traditional plant breeding techniques, has resulted in the development of the Cleancrop™ Brassica system. Seedlings of Brassica napus with increased chlorsulfuron resistance were identified following seed mutagenesis with ethyl methanesulfonate (EMS) and in vitro screening of seedlings in the presence of the herbicide. Surviving herbicide resistant seedlings were used in a traditional breeding program to introgress resistance into leafy turnip, bulb turnip, rape and swede. Acceptable herbicide resistance to at least a double application of chlorsulfuron from either a preemergence or a 4-leaf post emergence timing has now been produced in all these crops. Results from trials sown at Lincoln, Canterbury and Knapdale, Southland with chlorsulfuron herbicide application at both these timings with HT-S57 swede showed excellent weed control and no noticeable crop phytotoxicity. The preemergence herbicide application produced significantly more total dry matter per hectare than the untreated control. This weed management system represents a new tool for New Zealand farmers which will expand the use of forage brassica crops into more marginal areas which historically have had difficult to control weed problems. Keywords: Seed mutagenesis, chlorsulfuron, acetolactate synthase, field plant breeding, Cleancrop™ Brassica System, HT Brassica™