Table 2.

Characterization of the QS3D dPCR performance using the primer combination Ams06KbF/Ams189R, targeting a 627 bp DNA sequence.

Host	Log CFU mL−1 b	Log Copies mL−1 (±SD)c,d	Copies rxn−1 (±SD)d,e	# Qualified by QT (± SD)d,f	# Pos (±SD)d,g
Apple cv. Honeycrisp a	7.33	7.32 ± 0.06	4.406 ± 0.623	17353 ± 279	17057 ± 190
	6.33	6.37 ± 0.01	0.494 ± 0.014	17537 ± 195	6824 ± 183
	5.33	5.46 ± 0.06	0.061 ± 0.009	17205 ± 812	1021 ± 183
	4.33	4.42 ± 0.08	0.005 ± 0.001	17656 ± 381	93 ± 20
	3.33	3.62 ± 0.10	0.001 ± 0.000	17388 ± 339	14 ± 5
Pear cv. Bosc a	7.33	7.54 ± 0.10	4.328 ± 0.988	17725 ± 630	17351 ± 423
	6.33	6.62 ± 0.11	0.518 ± 0.126	15655 ± 602	7019 ± 1101
	5.33	5.57 ± 0.10	0.047 ± 0.010	17752 ± 829	802 ± 139
	4.33	4.57 ± 0.08	0.005 ± 0.001	17490 ± 393	80 ± 16
	3.33	3.62 ± 0.09	0.000 ± 0.000	17707 ± 705	8 ± 2

^aE. amylovora-free plant material was processed in a plastic bag containing 0.1xAMB in a ratio 1:50 (w/v), by hammering.

^bData shown in this column correspond to average bacterial concentrations of two different E. amylovora stocks, employed to inoculate samples in two independent assays performed in triplicate. Values in each dilution were calculated based on the stock concentrations. Hence, the SD in all cases was the same, ±0.24.

^cLog Copies mL⁻¹ = Log [copies μL⁻¹_rxn × 1/D_{rxn tube}  × 1/E_{DNA Extr}  × 1/Vol_Pl.Macerates]; i.e. Log (copies μL⁻¹_rxn × 1.79 × 10³) for Apple, and Log (copies μL⁻¹_rxn × 4.81 × 10³) for pear.

^dAverage values of two independent experiments performed in triplicate.

^eQuantity of target DNA copies, expressed in copies per reaction well.

^fTotal number of reaction wells in the chip fitting the selected quality threshold.

^gNumber of positive calls for FAM dye in the chip, as determined from the Review Calls scatter plot. Based on the no-template control and plant material negative control analysis, chips with 5 or less than 5 positive calls were considered negative for E. amylovora detection, and the provided dPCR values were not considered for quantification.