RELATIONSHIPS BETWEEN GENETIC-POLYMORPHISM AND HERBICIDE RESISTANCE WITHIN ALOPECURUS-MYOSUROIDES HUDS

The genetic structure of a gramineous weed (Alopecurus myosuroides Huds.) was investigated by an electrophoretic survey of seven enzyme systems on 19 susceptible and herbicide-resistant populations collected in different countries. The results indicate that Alopecurus myosuroides is an allogamous self-incompatible plant with a high level of genetic polymorphism (60 per cent of loci polymorphic, average heterozygosity = 0.21) and with a very low genetic differentiation among populations (Nei's distances less than 0.06) from wide geographical origins. A comparison of expected and observed levels of heterozygosity indicates no significant departure from random mating. Furthermore, there is no evidence of differences between resistant and susceptible populations in any genetic parameter. This is the first example of no change in genetic structure within resistant weed populations after herbicide selection.