IN VITRO SCREENING FOR RESISTANCE TO FIRE BLIGHT USING A PATHOGENICITY MUTANT OF ERWINIA AMYLOVORA

Detached leaves of in vitro pear plantlets (susceptible or resistant to fire blight), when infiltrated with a virulent strain of Erwinia amylovora, or with an heterologous pathogen Pseudomonas syringae pv. tabaci, show necrosis within 3 days, or electrolyte leakage within 40 hrs.
Disease reaction cannot be differentiated from the hypersensitive reaction (HR). Some dsp mutants of E. amylovora are known to be completely avirulent in compatible situations, but still capable of inducing HR in incompatible ones (at least on tobacco). We show here that these characteristics are maintained on in vitro detached leaves when using a susceptible cultivar (Doyenné du Comice) and a resistant cultivar (Old Home): no necrosis (or no electrolyte leakage) versus necrosis (or electrolyte leakage), respectively.
It can be concluded that i) Old Home resistance to fire blight involves an hypersensitive reaction, ii) this response can be induced on detached leaves of in vitro plantlets by a dsp mutant, iii) this in vitro bioassay could be useful for a primary screening of resistance by hypersensitivity in a mutagenized population of a susceptible cultivar as Doyenné du Comice.

VII International Workshop on Fire Blight

C. Pinet-Leblay, M.N. Brisset, E. Chevreau, J.-P. Paulin

https://doi.org/10.17660/ActaHortic.1996.411.85