Identification and Mechanism of Echinochloa crus-galli Resistance to Fenoxaprop-p-ethyl with respect to Physiological and Anatomical Differences

Table 1

Effect of fenoxaprop-p-ethyl on the susceptible and resistant biotypes of E. crus-galli expressed as the rates of the herbicide required for 50% reduction of the aboveground biomass (GR₅₀) and estimated resistance ratio.

Weed biotype	GR50 gm a.i/ha	b	c	d	R^2	R/S value	P value
Susceptible	3	1.47	0.72	97	0.99	—	<0.05
Resistant	36.21	1.79	1.35	100	0.99	12.07	<0.05

c: the mean response (fresh weight as percent of control) at very high herbicide rate.
d: the mean response (fresh weight as percent of control) at zero herbicide rate.
b: slope of the line.
GR₅₀: herbicide rate to reduce plant growth by 50% relative to untreated control.
R²: the coefficient of determination.
R/S ratio: the GR₅₀ of the resistant biotype divided by the GR₅₀ of the susceptible biotype.
𝑃 value: the probability of the obtained results.