THE RELATIONSHIP BETWEEN POPULATION OF Pseudomonas syringae pv. syringae AND INCIDENCE OF BACTERIAL APICAL NECROSIS OF MANGO IN EGYPT

A field study to evaluate the relationship between population size of Pseudomonas syringae pv. syringae and incidence of bacterial apical necrosis disease of mango was carried out during 2008 and 2009 on mango trees cv. Zebda in three commercial orchards located at lsmailia and Giza governorates and Noubaria region in Egypt. The largest population of Pseudomonas syringae pv. syringae was detected on diseased trees during the cool and wet periods that coincided with the highest disease incidence percentage; whereas on healthy trees, P. syringae pv. syringae was occasionally detected. The total bacterial populations isolated from mango buds were similar on healthy and diseased trees in all sampling dates and orchards. In both years, the mean population size of P. Syringae pv. syringae on buds of symptomatic trees in lsmailia orchard was relatively high when compared with those of Noubaria or Giza orchards. The maximum population of P. syringae pv. syrin-gae on buds exceeded 10^7 CFU/ g fresh weight in January and March in both years. Ice nuclei active values were related to the numbers of P. syringae in affected trees while In non affected trees, in which P. syringae pv. syringae was only occasionally detected, Ice nuclei were not observed. Close (Received October 7, 2010) (Accepted October 24, 2010) association was detected between the pathogen presence and the disease incidence. Similar results were observed on trees belonging to the same group.