Articles
THE PRESENCE OF ERWINIA AMYLOVORA IN ASYMPTOMATIC APPLE BUD WOOD: A THREAT TO NEWLY ESTABLISHED APPLE PLANTINGS
Article number
1056_38
Pages
235 – 238
Language
English
Abstract
The development of shoot blight in new apple plantings in NY occasionally seems to originate from infections at the site of budding.
Bud wood for new cultivars and those of limited availability is often collected from orchards where fire blight is established.
An investigation was undertaken to examine the presence of Erwinia amylovora in the bud wood from commercial apple trees used for nursery stock.
Bud wood was collected from two commercial orchards used for bud wood sources of Gala and Topaz apples in western NY. Individual replicated collections of buds were made from bud wood with differing proximities to shoot blight symptoms and evaluated for the presence of epiphytic and endophytic E. amylovora. On both cultivars, virulent E. amylovora was recovered from both the surface and the internal contents of buds from asymptomatic shoots.
For Topaz there were no significant (P>0.05) differences in the frequency of E. amylovora recovery in regards to proximity to observed shoot blight symptoms.
By contrast, the frequency of Gala buds from which E. amylovora was recovered from the internal tissues was significantly (P=0.034) higher for shoots within 1 m of a shoot blight strike (>80%) than for buds from shoots more than 20 m from a tree with a shoot blight strike (32%). Although it is unlikely that the majority of such cryptic infections will result in shoot blight, these observations may necessitate a reexamination of bud wood collection practices especially where streptomycin resistance has been detected.
Bud wood for new cultivars and those of limited availability is often collected from orchards where fire blight is established.
An investigation was undertaken to examine the presence of Erwinia amylovora in the bud wood from commercial apple trees used for nursery stock.
Bud wood was collected from two commercial orchards used for bud wood sources of Gala and Topaz apples in western NY. Individual replicated collections of buds were made from bud wood with differing proximities to shoot blight symptoms and evaluated for the presence of epiphytic and endophytic E. amylovora. On both cultivars, virulent E. amylovora was recovered from both the surface and the internal contents of buds from asymptomatic shoots.
For Topaz there were no significant (P>0.05) differences in the frequency of E. amylovora recovery in regards to proximity to observed shoot blight symptoms.
By contrast, the frequency of Gala buds from which E. amylovora was recovered from the internal tissues was significantly (P=0.034) higher for shoots within 1 m of a shoot blight strike (>80%) than for buds from shoots more than 20 m from a tree with a shoot blight strike (32%). Although it is unlikely that the majority of such cryptic infections will result in shoot blight, these observations may necessitate a reexamination of bud wood collection practices especially where streptomycin resistance has been detected.
Publication
Authors
D.I. Breth, E. Borejsza-Wysocka, S. Kuehne, H.S. Aldwinckle, C. Cox
Keywords
fire blight, nursery, bud wood, latent, asymptomatic
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