Table 1 Parameters of the log-logistic equationsa used to calculate the glyphosate rates required for 50% dry weight (GR50) and reduction survival (LD50), expressed as percentage of the mean untreated control of the A. hybridus population.

From: Multiple mutations in the EPSPS and ALS genes of Amaranthus hybridus underlie resistance to glyphosate and ALS inhibitors

Growth reduction (GR50)

Population

D

b

GR50 (g ae ha-1) ± SE

P-value

RIb

MR2

97.0

2.9

2222.0 ± 49.6

 < 0.001

125.5

S

100.8

1.5

17.7 ± 0.8

 < 0.001

–

Plant survival (LD50)

Population

d

b

LD50 (g ae ha-1) ± SE

P-value

RI

MR2

98.8

4.7

4508.3 ± 57.2

 < 0.001

93.6

S

100.9

4.1

48.2 ± 3.7

 < 0.001

–

  1. a Y = c + {(d-c)/[1 + (x/g)b]}, where d is the coefficient corresponding to the upper asymptote, c is the limit of the coefficient of the lower asymptote (fixed at 0 for GR50 and LD50), b is the slope of the line, x is the herbicide dose, and g is the dose at the inflection point and hence the GR50 or LD50. ± SE is the standard error of the mean (n = 10). The P-value is the level of significance of the non-linear regression model.
  2. bRI (resistance index) = GR50, or LD50 (MR2)/GR50, or LD50 (S).
Back to article page