Table 4 Parameter estimations of the equation used to calculate the concentration (µM) of the ALS inhibitor herbicides necessary to reduce the activity of the ALS enzyme by 50% (I50) in the two Amaranthus hybridus biotypes (MR2 and S).

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

Herbicide

Population

c

d

b

I50 (μM) ± SE

P-value

RIb

Tribenuron

MR2

1.5

97.7

0.7

272.7 ± 26.0

 < 0.001

5.7

S

0.1

94.2

0.8

47.5 ± 6.3

0.008

–

Florasulam

MR2

− 0.2

99.1

0.8

56.5 ± 9.0

 < 0.001

3.2

S

1.9

99.0

1.5

17.4 ± 1.4

 < 0.001

–

Flucarbazone

MR2

0.7

98.6

1.2

144.7 ± 11.5

 < 0.001

149.2

S

0.9

98.3

0.8

1.0 ± 0.1

 < 0.001

–

Byspiribac

MR2

1.7

98.4

0.6

2728.4 ± 80

0.011

59.5

S

− 0.9

98.7

0.8

45.9 ± 8.0

 < 0.001

–

Imazamox

MR2

− 1.5

100.0

1.1

3171.8 ± 111.9

0.016

27.1

S

1.9

99.3

1.2

117.0 ± 9.1

 < 0.001

–

  1. a Y = c + {(d–c)/[1 + (x/g)b]}, where c and d are the coefficients corresponding to the upper and lower asymptote, respectively; x herbicide concentration; b is the slope of the line; and g is the herbicide concentration at inflection point (I50). ± SE is the standard error of the mean. The P-value is the level of significance of the non-linear regression model.
  2. b RI (resistance index) = I50 MR2/I50 S.
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