POPULATION DYNAMICS OF ERWINIA AMYLOVORA ON DIFFERENT BLOSSOM ELEMENTS OF PEAR AND APPLE

T. Hasler, L. Mamming
Erwinia amylovora was applied by spraying bacterial suspensions on different blossom elements to investigate the question when and where the bacteria multiply. For this purpose blossoms of pear ‘Conférence’ and apple ‘Golden Delicious’ were inoculated with 108 cfu/ml. On ‘Conférence’ blossoms 2.8 x 104 cfu and on ‘Golden Delicious’ 5.6x 106 cfu of E. amylovora adhered respectively. At six time intervals the population was determined on the following blossom elements: petals, anthers, filaments, stigma, stylus and hypanthium. The lowest populations were found 6 h after inoculation. However, after the next 18 h the population of E. amylovora was increasing rapidly. This multiplication phase is normally already terminated after 48 h on anthers, stigmas and styli.
The highest division rate of the population was 0.6/h. On petals E. amylovora did not multiply. At 48h after inoculation a high population level was reached on different elements of the blossom which may lead to infection. Only on the styli of the pear variety ‘Conférence’ did the population continue to increase between 72h and 96h after inoculation. This experiment demonstrated that high bacterial populations develop not only on the stigma and stylus but also on the hypanthium, which is at the base of the blossom where also the nectaries are situated. This implies that for the development of infection a high relative humidity in the hypanthium, in order to liquefy the nectar, can probably be sufficient for an infection, and bacteria may not be washed down from the stigma or anthers to the infection site.
Hasler, T. and Mamming, L. (2002). POPULATION DYNAMICS OF ERWINIA AMYLOVORA ON DIFFERENT BLOSSOM ELEMENTS OF PEAR AND APPLE. Acta Hortic. 590, 181-184
DOI: 10.17660/ActaHortic.2002.590.26
https://doi.org/10.17660/ActaHortic.2002.590.26
English

Acta Horticulturae