Inheritance of susceptibility to ethametsulfuron herbicide muster in summer turnip rape (Brassica rapa L.)
The Brassica oilseed crops, Brassica rapa L., B. napus L., and B. juncea (L.) Czern. & Coss., carry the inherent property of tolerance to the acetolactate synthase–inhibiting herbicide ethametsulfuron. However, a self-compatible line of B. rapa subsp. oleifera (DC.) Metzg. susceptible to this herbicide was isolated through single-plant selection in a Canadian cultivar. The objective of the present study was to elucidate the genetic control of tolerance to this herbicide in B. rapa by using this susceptible line as a parent in crosses with tolerant lines. The susceptible line was crossed with two tolerant, self-incompatible lines of oleiferous B. rapa. The F2, B1 (F1 backcrossed to tolerant parent), B2 (F1 backcrossed to susceptible parent), F3, and B1S1 generation populations were generated from the crosses and were evaluated for tolerance to ethametsulfuron. A single-gene locus was found to be involved in the control of this trait, with the tolerant phenotype being completely dominant over the susceptible. No difference in tolerance was detected in the populations derived from reciprocal crosses, suggesting the absence of cytoplasmic effects in the control of this trait. As the parents differed for self-incompatibility, segregation for this trait was found in the F2 and backcross populations, as expected. However, self-incompatibility allele(s) did not exert any influence on segregation of the locus controlling tolerance to ethametsulfuron.