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

The genetic structure of a gramineous weed (Alopecurus myosuroides Hud s.) was investigated by an electrophoretic survey of seven enzyme syst ems 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 co mparison of expected and observed levels of heterozygosity indicates n o significant departure from random mating. Furthermore, there is no e vidence of differences between resistant and susceptible populations i n any genetic parameter. This is the first example of no change in gen etic structure within resistant weed populations after herbicide selec tion.