Initial field evaluation of sulfonylurea herbicide resistant sugarbeet from somatic cell selection

Field studies were conducted with a sugarbeet (Beta vulgaris L.) breeding line segregating for monogenic dominant sulfonylurea herbicide resistance conditioned by the Sur 1 allele and obtained from somatic cell selection. Sulfonylurea herbicide resistant and susceptible sublines were compared to each other and to the commercially available susceptible cultivar MONO-HY E4 in regards to root yield, sugar content, and processing purity. In addition, the response of MONO-HY E4 and the sulfonylurea resistant and susceptible counterparts to simulated carryover sulfonylurea residues in soil and to postemergence (POST) applications of selected sulfonylurea herbicides was evaluated. In the absence of herbicides, counterpart resistant and susceptible sugarbeets produced similar root yield, sugar content, and clear juice purity at both locations. Nicosulfuron applied preplant incorporated (PPI) at 9 g ai ha −1 to simulate carryover in soil had no effect on the growth of sugarbeets from the resistant population or from the susceptible MONO-HY E4 cultivar seeded immediately after application. Primisulfuron and chlorimuron applied PPI at 10 and 3 g ai ha −1 , respectively, caused over 95% visible injury to the susceptible MONO-HY E4 sugarbeet 6 weeks after treatment (WAT), but had no adverse effect on the growth of resistant sugarbeet. POST application of primisulfuron at 40 and 80 g ai ha −1 , and thifensulfuron at 4 and 8 g ha −1 (one and two times the normal field use rate for corn and soybean, respectively), caused less than 15% visible injury to the resistant sugarbeet 4 WAT, but caused severe injury to the susceptible MONO-HY E4 sugarbeet. The sulfonylurea resistant sugarbeet was tolerant to POST applications of primisulfuron at four times and thifensulfuron at two times the field use rate. This magnitude of resistance is great enough for effective use of primisulfuron and thifensulfuron for weed control in sulfonylurea resistant sugarbeet