Inheritance of resistance to anti-microtubule dinitroaniline herbicides in an "intermediate" resistant biotype of Eleusine indica (Poaceae).

Inheritance of resistance to the anti-microtubule dinitroaniline herbicides was investigated in a goosegrass biotype displaying an intermediate level of resistance (I). Reciprocal crosses were made between the I biotype and previously characterized susceptible (S) or resistant (R) biotypes. Eight F(1) hybrids were identified, and F(2) populations were produced by selfing. The dinitroaniline-herbicide response phenotype (DRP) of F(1) plants, and F(2) seedlings was determined using a root-growth bioassay. The DRP of F(1) plants of S × I was "susceptible" (i.e., identical to the S parental plants), and the DRP of F(1) plants of I × R was "intermediate" (i.e., identical to the I parental plants). Nonparental phenotypes were not observed in F(1) plants. Results indicated susceptibility to be dominant over intermediate resistance and intermediate resistance to be dominant over high resistance. Analysis of reciprocal crosses ruled out any role for cytoplasmic inheritance. When treated at the discriminating concentration (e.g., 0.28 ppm oryzalin), F(2) seedlings of S × I were classified as either S or I phenotype, and F(2) seedlings of I × R were classified as either I or R phenotype. Again, nonparental phenotypes were not observed. The 3:1 (S:I or I:R) segregation ratios in F(2) seedlings were consistent across all eight F(2) families. The results show that dinitroaniline herbicide resistance in the I biotype of goosegrass is inherited as a single, nuclear gene. Furthermore, it suggests that dinitroaniline resistance in goosegrass is controlled by three alleles at a single locus (i.e., Drp-S, Drp-i, and Drp-r).