Figure 1.
Symptoms of C. pepo ssp. texana plants infected with ZYMV and E. tracheiphila.
(A) Healthy plant mock-inoculated for both viral and bacterial diseases; (B) Plant with E. tracheiphila wilt symptoms; (C) ZYMV-infected plant; (D) ZYMV-infected plant co-infected with E. tracheiphila and showing both virus and bacterial wilt symptoms.
Figure 2.
Salicylic acid responses of healthy and ZYMV-infected plants.
Mean salicylic acid (+/- SE) measured 48hr after E. tracheiphila (or mock) inoculation. Untouched = healthy controls; Mock = mock virus inoculation; ZYMV = virus-infected. Open bars designate uninfected plants subjected to mock-inoculation with E. tracheiphila; hatched bars designate plants inoculated with E. tracheiphila. Letters indicate significant differences (P < 0.05 in a Tukey-Kramer test). Sample sizes (E. tracheiphila free : E. tracheiphila-infected): Untouched (14 : 14); Mock (14 : 13); ZYMV (15 : 12).
Figure 3.
Phytohormone responses of healthy, E. tracheiphila-inoculated, and ZYMV-infected plants to cucumber beetle herbivory.
Levels of the phytohormones SA and JA measured 15h after exposure to cucumber beetles. (A) mean salicylic acid production ± SE; (B) mean cis-JA ± SE. Mock = mock virus inoculation; Erwinia = inoculation with E. tracheiphila; ZYMV = inoculation with ZYMV. Open bars designate the undamaged treatment; Striped bars designate beetle-herbivory treatments. Letters indicate significant differences (P < 0.05 in a Tukey-Kramer test). Sample sizes (without herbivory : herbivory): Mock (13 : 12); Erwinia (12 : 10); ZYMV (13 : 13).
Figure 4.
E. tracheiphila disease progression in healthy and ZYMV-infected plants after low-dose inoculations.
Disease progression over 26 days for 62 healthy (mock-inoculated) plants, and 65 ZYMV-infected plants following artificial inoculation with infectious cucumber beetle frass.
Figure 5.
E. tracheiphila disease progression in healthy and ZYMV-infected plants after high-dose inoculations.
Disease progression over 45 days for untouched controls (n=49), mock-virus-inoculated (n = 50), and ZYMV-infected (n = 47) plants following inoculation with a homogenate of infectious cucumber-beetle frass supplemented with in vitro cultured E. tracheiphila. Lines with closed symbols track the initial onset of wilt symptoms; lines featuring open symbols track complete plant collapse due to wilting.
Figure 6.
Timing of appearance of systemic wilt symptoms on plants within the high dose inoculation experiment.
Bars represent mean day post inoculation of appearance of systemic symptoms (on a non-inoculated leaf) for untouched control (n = 49); mock (n = 50); and ZYMV-infected (n = 47) plants. Letters indicate significant differences (P < 0.05 by a Tukey-Kramer test).