ELECTROPHORETIC VARIATION IN TRIAZINE-RESISTANT AND SUSCEPTIBLE POPULATIONS OF AMARANTHUS RETROFLEXUS L

Area of Science:

• Plant genetics
• Evolutionary biology
• Agricultural science

Background:

• Herbicide resistance in weeds is a significant agricultural challenge.
• Amaranthus retroflexus (pigweed) is a common agricultural weed.
• Triazine herbicides are widely used, leading to resistant weed populations.

Purpose of the Study:

• To investigate electrophoretic variation in enzyme systems of triazine-resistant and susceptible Amaranthus retroflexus populations.
• To compare genetic diversity between resistant and susceptible weed populations.
• To understand the impact of herbicide selection on weed genetic structure.

Main Methods:

• Electrophoretic analysis of seven enzyme systems (IDH, GOT, 6PGD, PGI, LAP, MDH, GDH).
• Sampling of one triazine-resistant and nine susceptible Amaranthus retroflexus populations across a north-south transect in Ontario.
• Comparison of genetic variation patterns between resistant and susceptible populations.

Main Results:

• The triazine-resistant population showed a significant reduction in genetic variation compared to susceptible populations.
• Six enzyme systems (IDH, GOT, 6PGD, PGI, LAP, MDH) exhibited phenotypic polymorphism, while GDH was monomorphic across all populations.
• The resistant population was polymorphic for only three of the seven enzyme systems studied, contrasting with susceptible populations.

Conclusions:

• Founder effects likely contributed to the reduced genetic diversity in the triazine-resistant Amaranthus retroflexus population.
• Intensive atrazine use has led to genetic simplification in resistant weed populations.
• Genetic diversity patterns in susceptible populations were not correlated with habitat or latitude.