The genetic inheritance of herbicide resistance in weeds

The number of herbicide-resistant weeds is increasing globally. A successful management practice requires an understanding of how resistance traits are inherited. Weed scientists worldwide have investigated the mode of inheritance for herbicide resistance in weeds. Depending on the resistance gene/mechanism, varied patterns of inheritance have been documented in weed species. In most of the target-enzyme mechanism cases, the mode of inheritance involves a single nuclear gene. However, maternal (cytoplasmic) inheritance has also been documented for triazine-resistant weeds with the target-enzyme mutation mechanism of resistance. Resistance from target-enzyme overexpression is not always associated with the single-gene model of inheritance. Depending on the type of resistance, allelic dominance varies between complete dominance, semi-dominance and recessive for both target-enzyme mutation and target-enzyme overexpression mechanisms. The nontarget site mechanism of resistance is however, more complex. The pattern of inheritance in weeds with nontarget site resistance is quite variable and should be investigated case by case. The pattern of inheritance has a crucial role in the dynamics of herbicide-resistance within a weed population, and knowledge about the inheritance of herbicide resistance traits could help develop predictive models and novel strategies to prevent the spread of resistance allele(s).