ABSTRACT
This chapter provides a basis for examining the questions that are relevant to understanding herbicide resistance evolution and that may determine appropriate weed management strategies. Herbicide resistance is a result of selection for traits that allow weed species to survive specific management practices which would otherwise cause mortality. There are two precursors for the evolution of a trait like herbicide resistance in plant populations: the occurrence of heritable variation for the trait, and natural selection. R. E. Lenski and J. E. Mittler suggested that variable mutation rates may be an evolved response that promotes increased genetic variation under stress, but further stated that there is only weak evidence for directed mutation. In any case the rate of resistance evolution by quantitative inheritance could be influenced quite differently by the same factors that effect single gene-inherited resistance. Theoretically at least, in a random mating diploid population, one generation of self-fertilization leads to an average reduction in heterozygosity of 50%.
