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ARS Home » Northeast Area » Geneva, New York » Plant Genetic Resources Unit (PGRU) » Research » Publications at this Location » Publication #212266
Title: Fire Blight Resistance of Budagovsky 9 Apple Rootstock

Author
item RUSSO, NICOLE - CORNELL UNIVERSITY
item ROBINSON, TERENCE - CORNELL UNIVERSITY
item Fazio, Gennaro
item ALDWINCKLE, HERBERT - CORNELL UNIVERSITY

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2007
Publication Date: 3/5/2008
Citation: Russo, N., Robinson, T., Fazio, G., Aldwinckle, H. 2008. Fire Blight Resistance of Budagovsky 9 Apple Rootstock. Plant Disease. 92(3):385-391.

Interpretive Summary: The apple rootstock Budagovsky 9 (B.9) developed in Eastern Europe has shown field resistance in the US to fire blight infections. When this rootstock was tested as an ungrafted plant by inoculating actively growing apical meristems it showed high susceptibility to fire blight. This discrepancy was investigated in a battery of field and laboratory trials. Two clonal varieties of B.9 were tested with other susceptible and resistant controls. Results of these trials confirm resistance of B.9 and support the hypothesis that field resistance of B.9 is due to developmental differences between immature and mature (hardened) tissue.

Technical Abstract: Erwinia amylovora the causal agent of fire blight can result in a fatal infection of the apple rootstock known as rootstock blight. Budagovsky 9 (B.9) apple rootstock is reported to be highly susceptible to rootstock blight, although multiple field trials report B.9 to be resistant to rootstock blight infection. Conflicting results may stem from genetic variation in the clonal B.9 population, based on phenotypic differences in rootstock material. Genetic testing, using twenty-three microsatellite loci, confirmed the clonal uniformity of B.9 currently in commerce. Variation in growth habit between B.9 rootstocks originating from two nurseries has also been discounted as a source of disease resistance. Inoculation of grafted and non-grafted shoot tissue versus woody rootstock tissue has revealed the existence of a novel resistance phenotype. B.9 rootstock are susceptible to leaf inoculation by E. amylovora, statistically similar to the susceptible rootstock Malling 9 (M.9). Conversely, inoculation assays targeting mature tissue reveal a high degree of resistance in B.9, whereas M.9 remains susceptible. Although the mechanism by which B.9 develops resistance is unknown, our results support the development of adult plant resistance in B.9 apple rootstock. Durable fire blight resistance correlated with tissue development could be a valuable tool for rootstock breeders.