Factors influencing ingress of Xanthomonas pruni through peach leaf scars and subsequent development of spring cankers
Feliciano, A.; Daines, R.H.
Phytopathology 60: 1720-1726
Leaf scars, obtained by the forcible removal of the entire leaf or by delaminating the petioles 7 days prior to their removal, were inoculated immediately and semimonthly from 15 July to 1 November with Xanthomonas pruni. The scars were located either at the tip or one third of the way down the twig. Summer cankers were produced following inoculations performed from 15 July to I October, whereas spring cankers resulted from inoculations made from 17 September to 1 November. Ingress of X. pruni occurred only at fresh scars resulting either from the forcible removal of leaves or from the removal of petioles that had been delaminated 1 and 3 days. Inoculated scars at the tip developed many more spring cankers than those one third of the way down the twigs. Histopathological investigations disclosed that X. pruni can enter the twig through the xylem vessel and intercellular spaces in the leaf base. Entrance through the xylem vessels appeared to be of no pathological importance, however, since the bacteria, once inside, could not move out to infect neighboring cells. Bacteria survived the winter in the intercellular spaces of the cortex, phloem, and xylem parenchyma and initiated cankers the following spring.