Growth and yield responses of Italian ryegrass to diclofop-methyl and ozone

MARTINEZ-GHERSA, M.A.; OLSZYK, D.; RADOSEVICH, S.R.

WEED RESEARCH

European Weed Reseach Society

Año: 2008 vol. 48 p. 68 - 77

0043-1737

We evaluated the combined effects of diclofop-methyl herbicide application and the air pollutant ozone (O3) on diclofop-methyl-resistant and -susceptible biotypes of Italian ryegrass (Lolium multiflorum). We conducted two experiments, one with a long vegetative growth period and the other with a short vegetative growth in late spring with seed production in summer. As expected, because of its phytotoxicity, the herbicide alone reduced total vegetative biomass, leaf area, tillernumber and seed production at most sampling periods in susceptible plants for both experiments. However, it had variable effects on resistant plants, including a positive effect on seed production. Ozone alone delayed vegetative biomass accumulation and reduced leaf areaand seed biomass in both experiments. However, the effects of O3 on some parameters were altered by herbicide rate and ⁄ or biotype. Especially notable was a greater reduction in seed biomass because of O3 in resistant than in susceptible plants with no herbicide. If these apparent differential responses to herbicide and O3 stress of susceptible and resistant plants are confirmed and persist over time, evolutionary tradeoffs may occur. For example, the frequency of resistant plants in a population may be altered in response to interactions between herbicides and other anthropogenic stresses.