Screening Soybeans for Tolerance to Metribuzin1

Studies were initiated to develop a nutrient culture technique to select soybean [Glycine max (L.) Merr.] cultivars or breeding lines for tolerance to the herbicide metribuzin [4‐amino‐6‐tert‐butyl‐3‐(methylthio)‐as‐triazine‐5(4H) one]. Forty‐five soybean cultivars, representing determinate and indeterminate types commonly grown in the U.S., were screened in a modified Hoagland's nutrient culture containing 0.125 ppm metribuzin. Two cultivars, ‘CNS’ and ‘Wayne,’ and one breeding line, D66‐5566, were the most tolerant, showing only slight injury, whereas ‘Semmes’ and ‘Tracy’ were killed. Metribuzin caused severe injury to ‘Amsoy,’ ‘Chippewa 64,’ ‘Corsoy,’ ‘Clark 63,’ ‘Custer,’ ‘Delmar,’ ‘Arksoy,’ ‘Peking,’ ‘Dorman,’ and ‘Bragg.’ The remaining 30 cultivars were moderately injured. This technique will be useful in breeding programs to select for metribuzin tolerance.