|Harshman, Julia - Washington State University|
|Evans, Kate - Washington State University|
|Allen, Haley - Washington State University|
|Asldwinckle, Herb - Cornell University - New York|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2017
Publication Date: 9/15/2017
Citation: Harshman, J., Evans, K., Allen, H., Potts, R.J., Flamenco, J.A., Asldwinckle, H.S., Wisniewski, M.E., Norelli, J.L. 2017. Fire blight resistance in wild accessions of Malus sieversii. Plant Disease. 101(10):1738-1745.
Interpretive Summary: Since genetic diversity is often lost during crop domestication, accessions of Malus sieversii, the wild progenitor of the domesticated apple, represent a valuable resource for disease resistance. Nearly 200 accessions of Malus sieversii from a USDA-ARS collection were selected as potential sources of disease resistance for apple scion breeding. Based upon controlled challenges with the fire blight pathogen at both Wenatchee, Washington and Kearneysville, West Virginia, 12 wild Malus sieversii accessions were identified as resistant to fire blight with resistance comparable to highly resistant Malus × robusta 5 and resistant 'Delicious'. These M. sieversii accessions will be used as parents in future crosses in apple breeding programs.
Technical Abstract: Fire blight (Erwinia amylovora) is a devastating bacterial disease in apple that results in severe economic losses. Epidemics are becoming more common as susceptible cultivars and rootstocks are being planted, and control is becoming more difficult as antibiotic-resistant strains develop. Resistant germplasm currently being utilized by breeding programs tend to have small fruit size and poor flavor characteristics. Malus sieversii, a progenitor species of domestic apple, is notable for its relatively large, palatable fruit and some accessions have been reported to be resistant to fire blight. In this study, nearly 200 accessions of M. sieversii and appropriate controls were inoculated with E. amylovora in both Washington and West Virginia to identify fire blight resistant accessions. Twelve accessions were identified with resistance comparable to highly resistant and resistant controls. Several accessions exhibited a unique resistance response, not previously reported in domestic apple (M. × domestica), characterized by low incidence of infection but high severity once infection was initiated. Several of these M. sieversii accessions will be used as parents in future crosses in the Washington State University apple breeding program.