Systemic colonization of potato plants resulting from potato haulm inoculation with Dickeya solani or Pectobacterium parmentieri

Figures & data

Fig. 1 Microscopic images of leaf tissues after spray-inoculation with a GFP-tagged strain of Dickeya solani, or mock-inoculated. Green fluorescent bacterial cells or signals in the images are indicated with an arrow. (a) Confocal laser scanning microscopy (CLSM) image of a stoma on the adaxial side of an inoculated potato leaf. (b) Mock-inoculated. Leaflets sampled at 1 day after inoculation, were incubated overnight on water agar at 25°C prior to observation. Photomicrographs were taken with a 40x (a) or 10× (b) objective lens. (c) Epifluorescence stereomicroscopy (ESM) image of a stoma on the adaxial side of an inoculated potato leaf. (d) Mock-inoculated. Leaflets were sampled 7 days after inoculation and incubated on water agar for 2 days at 25°C to support bacterial growth. Photomicrographs were taken with a 20× (c) or 40× (d) objective lens. (e) CLSM image of a hydathode of an inoculated potato leaf. (f) Mock-inoculated. Leaflets sampled at 0 dpi were placed on water agar and incubated overnight at 25°C prior to observation. Photomicrographs were taken with a 40× objective lens. (g) CLSM image of vascular tissue of the abaxial side of an inoculated potato leaf. (h) Mock-inoculated. Photomicrographs were taken with a 10× objective lens 7 days after inoculation. (i and j) ESM images of the adaxial side of wounded potato leaf tissue. Leaflets were collected shortly after leaf inoculation, placed on water agar and incubated overnight at 25°C prior to observation. Notice the striped pattern of the infected tissues consistent with the striped pattern of the superficial wounds at the time of inoculation. Photomicrographs were taken with a zoom magnification objective at 10×

Table 1. Progress of soft rot Pectobacteriaceae colonization process¹ in wounded leaves during the 2013 and 2014 systemic colonization experiments

	Samples			Dickeya solani							Pectobacterium parmentieri
Experiment	Time	Number^2		Disinfected^3				Not disinfected^4			Disinfected				Not disinfected
				10^2	10^4	10^6		10^2	10^4	10^6	10^2	10^4	10^6		10^2	10^4	10^6
2013	0 dpi^5	3		0	0	67		0	67	100	0	0	67		0	100	100
2013	1 dpi	4		50	100	100		25	100	100	0	50	100		50	100	100
2013	21 dpi	4		75	100	100		75	100	100	50	50	100		25	50	100
2013	42 dpi	4–5		100	100	100		100	100	100	100	100	100		100	100	100
2014	0 dpi	3		0	0	0		0	0	0	0	0	0		0	0	33
2014	1 dpi	4		50	25	75		25	50	75	0	0	50		0	100	100
2014	21 dpi	4		75	50	100		75	100	100	0	0	75		0	50	75
2014	35 dpi	4–5		0	50	100		0	75	100	0	0	0		0	0	0

¹the progress of the colonization process is expressed as the percentage leaf extracts found positive for D. solani or P. parmentieri after plating of extracts of leaves sampled 0, 1, 21, 35 or 42 days after inoculation with pathogen suspensions with inoculum densities of 10², 10⁴ or 10⁶ cfu mL^{−1. 2} number of plants sampled per time point. ³ numbers in columns with heading ‘Disinfected’ represent percentages leaves with internal populations (i.e. infections) of D. solani or P. parmentieri. ⁴ numbers in columns with heading ‘Not disinfected’ represent percentages leaves with both external and internal populations of D. solani or P. parmentieri. ⁵ dpi: days post inoculation

Fig. 2 Population densities of Dickeya solani and Pectobacterium parmentieri (respectively, the upper and lower row of graphs) in leaves at 0, 1, 21 and 42 days after spraying potato leaves with suspensions of 10², 10⁴ or 10⁶ cfu mL⁻¹. Results are summarized of the glasshouse experiment in 2013. W = leaves wounded prior to inoculation, NW = leaves not wounded prior to inoculation, D = leaves disinfected prior to analysis, ND = leaves not disinfected prior to analysis. Error bars show standard deviations

Fig. 3 Population densities of Dickeya solani and Pectobacterium parmentieri (respectively, the upper and lower row of graphs) in leaves at 0, 1, 21 and 35 days after spraying potato leaves with suspensions of 10², 10⁴ and 10⁶ cfu mL⁻¹. Results are summarized of the glasshouse experiment in 2014. W = leaves wounded prior to inoculation, NW = leaves not wounded prior to inoculation, D = leaves disinfected prior to analysis, ND = leaves not disinfected prior to analysis. Error bars show standard deviations

Fig. 4 Average densities of Dickeya solani and Pectobacterium parmentieri (respectively, the upper and lower row of graphs) in leaves, in top or base parts of potato stems, in stolons or in tubers at 42 days post-inoculation in the experiment conducted in 2013. Bars indicate standard deviations. Plants were inoculated with 10², 10⁴ or 10⁶ cfu mL⁻¹ of Dickeya solani or Pectobacterium parmentieri on leaves that were wounded or not wounded prior to inoculation

Fig. 5 Population densities of Dickeya solani (Dsol) and Pectobacterium parmentieri (Ppar) in foliage tissue at 0, 3, 5 and 14 days after chopping the haulms followed by herbicide treatment of the stalks (Mech.) or after chemical vine killing (Chem.). Haulms were spray-inoculated with 10⁸ cfu mL⁻¹ 5 days before haulm destruction

Fig. 6 Population densities of Dickeya solani (Dsol) and Pectobacterium parmentieri (Ppar) in foliage, soil or tubers at 0 and 14 days after chopping the haulms followed by herbicide treatment of stalks (Mech.) or after chemical vine killing (Chem.)