Downy mildew disease promotes the colonization of romaine lettuce by Escherichia coli O157:H7 and Salmonella enterica

Table 1 Effect of romaine lettuce susceptibility to downy mildew on the multiplication of EcO157 in leaf tissue in three replicate experiments

	Log-10 increase in EcO157 population size on leaf tissue of two lettuce accessions ^a
	Experiment 1 ^b			Experiment 2			Experiment 3
Tissue	RH	TT		RH	TT		RH	TT
Healthy	1.1 A	1.2 A	(0.301)^c	0.9 A	0.7 A	(0.420)	0.3 A	0.5 A	(0.552)
Chlorotic	1.1 A	2.5 B	(0.012)	2.1 B	1.8 B	(0.124)	1.2 B	1.3 B	(0.877)
Necrotic	2.8 B	3.2 B	(0.140)	2.4 B	3.1 C	(0.002)	2.3 C	3.1 C	(<0.0001)
	0.0006^d	0.0015		<0.0001	<0.0001		<0.0001	<0.0001

^aRomaine lettuce accessions tested were RH08-0464 (RH) and Triple Threat (TT) with low and high susceptibility to downy mildew, respectively.
^bIncrease in EcO157 population size on the two lettuce accessions was assessed at 18, 20 and 20 h post-inoculation in replicate experiment 1, 2, and 3, respectively.
^cValues in parenthesis are P values resulting from the t-test between RH and TT for the type of tissue within the experiment.
^dValues at the bottom of each column are P values resulting from ANOVA on the different types of tissue within plant accession and experiment. Different letters within column indicate means that are significantly different at P < 0.05. Significant differences were determined using the Tukey- Kramer procedure for multiple comparisons.

ISSN: 1471-2180