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. 2018 Feb 19;9:199. doi: 10.3389/fpls.2018.00199

FIGURE 5.

FIGURE 5

Defense responses observed in root vascular tissues of resistant pea accessions after inoculation with Fop race 2. Black arrows indicate fungus. (A) Cross-section of the resistant accession JI1412 at 7 dpi stained with TBO showing carbohydrate accumulation (dark purple staining indicated by Black arrowheads) between vascular cells and entering infected xylem cells (red circle) to trap fungal cells (Black arrows). The turquoise blue coloration accumulating within and between completely plugged vascular cells (Green arrowheads) corresponds to polyphenols and the clear purple staining (Red arrowheads) to other filling substances. (B) Cross-section of the resistant accession P633 at 7 dpi stained with AGS showing accumulation of polyphenols (red staining indicated by Green arrowheads), carbohydrates (green staining indicated by Black arrowheads) and other filling substances (dark red staining indicated by Red arrowheads) within and between vascular cells. (C) Cross-section of the resistant P42 roots at 7 dpi stained with AGS showing accumulation of polyphenols (red staining indicated by Green arrowheads) and carbohydrates (green staining indicated by Black arrowheads) and other filling substances (dark red staining indicated by Red arrowheads) within and between vascular cells. (D) The same as (C) observed under epi-fluorescence showing the fluorescent emission of polyphenols (Green arrowheads). Black arrowheads indicate carbohydrates and Red arrowheads indicate other non-fluorescent filling substances. (E) TBO-stained cross-section of the resistant accession JI1412 roots at 7 dpi showing the cell wall strengthening of xylem cells (+). Asterisk indicates a normal vessel as a reference. Note also the accumulation of phenolics between xylem parenchyma cells and in the lumen of some xylem cells (turquoise green staining, Green arrowheads) and accumulation of other filling substance in some of these xylem cells (clear purple staining, Red arrowheads). (F) TBO-stained longitudinal section of the resistant accession JI1412 at 7 dpi showing the filling of a xylem vessel by carbohydrates originating from intercellular vascular cells progressively plugging the xylem vessel (Black arrowheads). Bar = 25 μm.