Table 3 Parameter estimates of the equationa used to calculate the glyphosate concentration (µM) needed to reduce the activity of the EPSPS 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

Species

Biotype

c

d

b

I50 (μM) ± SE

P-value

RIb

A. hybridus

MR2

8.5

99.3

0.9

59.1 ± 6.7

 < 0.001

111.5

S

0.8

100.6

1.0

0.5 ± 0.0

 < 0.001

–

  1. aY = c + {(d–c)/[1 + (x/g)b]}, where c and d are the coefficients corresponding to the upper and lower asymptote, respectively; x is the glyphosate concentration; b is the slope of the line; and g is the glyphosate 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. bRI (resistance index) = I50 MR2/I50 S.
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