Sensitivity of Bacterial Isolates from Eggs of A phis pomi to Erwinia amyloyora Bacteriophages12

Abstract

Bactrial isolations from eggs of the apple aphid, Aphis pomi De Geer, were made during the winters of 1961-62 and 1962-63. In the former, eggs were surface sterilized by immersion in a 10% commercial hypochlorite solution after which aliquots of crushed and uncrushed eggs were cultured in nutrient yeast dextrose broth (NYDB) and then plated on nutrient yeast dextrose agar (NYDA). In the latter, eggs were accumulated on NYDA plates in groups of 20 and strips of the agar medium containing eggs were ground in NYDB, the homogenate incubated for 18 hr at 28°C, and plated on NYDA. Bacteriophage specific for the fireblight organism ( Erwinia amylovora ) was applied to each plate and in 12 hr read for confluent lysis. A total of 156 bacterial isolates was obtained which could be grouped into 15 categories based on colony morphology. Virulence was ascertained by inoculation into plant tissue. Three categories predominated: white rough; yellow mucoid; and white smooth. Of these, 14 of the 46 white rough isolates were sensitive to the phage but avirulent. None of the yellow mucoids were sensitive although one proved virulent in apple tissue. One white smooth isolate was sensitive and virulent. The remaining isolates were insensitive and avirulent.