Articles
DETECTION OF SYSTEMIC SPREAD OF ERWINIA AMYLOVORA THROUGH SYMPTOMLESS APPLE SCION TISSUES INTO THE ROOTSTOCKS
Evidence was obtained of systemic spread of E. amylovora cells through internal tissues of symptomless scion shoots, down into the rootstock.
In one experiment, tips of potted single-shoot Empire and Idared trees on M.26 were inoculated in the greenhouse with E. amylovora strain Ea273. E. amylovora was detected in grindates by direct plating on CCT medium and by enrichment in Kado 523 broth followed by plating on CCT. Within 27 days of inoculation, E. amylovora was detected by direct plating in M.26 rootstocks of Empire and Idared trees.
In another experiment, tips of potted single-shoot Empire and Golden Delicious trees on M.26 were inoculated as above.
One-cm-long segments of shoots were surface sterilized, ground in phosphate buffer, and plated on semi-selective media (MMS). Grindates were also plated on Nutrient Agar; after 48 h, washings were assayed by PCR using 17-mer primers from the E. amylovora 29kb plasmid (from K. Geider). Within 11 days of inoculation, E. amylovora was detected in symptomless scion tissue > 50 cm below the shoot-tip in Empire and Golden Delicious, and in 2-year-old tissue in Golden Delicious.
By 21 days, E. amylovora was detected in the M.26 rootstock of Empire trees and by 41 days, in the M.26 rootstock of Golden Delicious trees.