ABSTRACT
This chapter reviews research on ecological and physiological characteristics of resistant (R) and susceptible (S) weeds to assess the impact of resistance on relative fitness in the absence of the herbicide selector. Long-term prevention and management of herbicide resistance will require adopting practices that reduce selection pressures that favor resistant plants. Reproductive success is determined by pollen and seed production throughout the life cycle of the plant. However, growth of isonuclear R and S biotypes of Solanum nigrum and S. vulgaris and photosynthetic rates of S. vulgaris were not affected differently by growth or measurement temperature. Ghersa examined germination phenology of diclofop-methyl R and S Lolium multiflorum biotypes in a wheat field. Seeds from sulfonylurea R and S L. serriola were collected from field-grown plants, and used in field burial studies. In the case of multiple resistance in L. rigidum from Australia, fitness differences between R and S biotypes are not apparent.
