ISHS Acta Horticulturae 338: VI International Workshop on Fireblight
SURVIVAL OF ERWINIA AMYLOVORA ON APPLE AND PEAR POLLEN |
| Authors: | T. van der Zwet, R.L. Bell |
| Abstract:
Pollen is one of many means by which Erwinia amylovora may be disseminated. Prior to and during pear and apple bloom, numerous tissues were collected and examined for the presence of E. amylovora. Blossom buds at the dormant, tight cluster, and open cluster stages of Bartlett pear and Jonathan apple were collected. Five intact and five crushed buds were placed in Erlenmeyer flasks containing 50ml of nutrient yeast dextrose broth (NYDB). The flasks were shaken at 160 rpm at room temperature for 24 hours and 100μl of turbit solution from each flask was pipetted onto NYDA plates. Colonies suspected to be E. amylovora were purified by triple streaking on NYDA media. These same procedures were used to process popcorn (Bartlett) and full pink (Jonathan) stages of bud development. During full bloom, anthers, pistils, sepals, petals, and whole flowers were processed individually on NYDA media. In addition, whole pear and apple blossoms were processed through a #10 sieve, used to collect anthers for pollination extraction. Collected pollen and anthers from 5 blossoms each were placed in NYDB, shaken, and plated on NYDA. At full bloom, Bartlett and Jonathan blossoms were also collected in zip-lock baggies containing buffer and 100μl of buffer solution was plated on NYDA. In addition large amounts of pear and apple pollen were collected through the sieve. Three vials each were placed in cold storage at 3C, –20C, or –80C, and pollen are to be examined after 2 and 6 months. Dry, zip-lock baggies with whole blossoms were also stored at these temperatures. Finally, control apple and pear blossoms were artificially inoculated with 108 cfu/ml of an aqueous súspension of E. amylovora. Blossoms were plated immediately and were stored at the above listed cold storage conditions. After 2 and 6 months of storage, E. amylovora was recovered only from the artifially inoculated blossoms. It should be remembered, however, that 1992 was not a blossom blight year and bacterial populations may have been extremely low. | |
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