MONITORING ERWINIA AMYLOVORA IN POME FRUIT ORCHARDS USING REVERSE-DOT-BLOT HYBRIDIZATION

Fire blight is an important disease in the interior of British Columbia although it only occurs sporadically.
For this reason a reliable quantitative system for monitoring build-up of Erwinia amylovora population would be useful to growers.
Previous research has shown that the reverse-dot-blot DNA hybridization test can be used to detect fungal and bacterial pathogens at the level of species.
The test can be made quantifiable when gray scale values are used to indicate the relative amount of DNA present.
The test was evaluated for E. amylovora by inoculating ‘Jonagold’ blossoms with known concentrations of E. amylovora.
E. amylovora was recovered daily and quantified over a five day period using dilution plating and gray scale values provided by DNA hybridization.
The two methods for counting cell populations generally corresponded except that the DNA test was more sensitive in detecting populations less than 10³ CFU/ml.
The number of blighted shoots on inoculated trees also increased with higher recorded populations.
When the reverse-dot-blot hybridization test was used to detect E. amylovora in randomly sampled apple and pear blossoms in 2003 it was negative.
The test did detect E. amylovora in leaves following predicted fire blight infection periods.
Hybridization of bacterial DNA from field samples that looked blighted did not reveal E. amylovora, however a separate PCR test conducted on the samples was positive for Pseudomonas syringae suggesting that the symptoms were due to bacterial blast rather than fire blight.

X International Workshop on Fire Blight

P.L. Sholberg, D. O´Gorman, K.E. Bedford

fire blight, apple, blossoms, DNA, PCR, model, diagnostic technique

https://doi.org/10.17660/ActaHortic.2006.704.10