The fire blight resistance QTL on LG7 of Malus ×robusta 5 is not dependent on the avrRpt2EA 156 S/C amino acid switch

• Published in: Journal of Plant Pathology Vol. 106; no. 3; pp. 1031 - 1038
• Main Authors: Emeriewen, Ofere Francis, Reim, Stefanie, Richter, Klaus, Wöhner, Thomas, Flachowsky, Henryk, Aldwinckle, Herb, Peil, Andreas, Fazio, Gennaro
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.08.2024
• Subjects: Biomedical and Life Sciences; Life Sciences; Plant Sciences; Short Communication; Mr5; LG7 resistance locus; Strain-specificity; Cysteine-serine SNP
• ISSN: 2239-7264
• DOI: 10.1007/s42161-023-01458-2

Malus × robusta 5, which has been the subject of extensive fire blight resistance research over time, is highly resistant or susceptible to the fire blight-causative bacterial pathogen, Erwinia amylovora – depending on the strain. M . × robusta 5 has been crossed with susceptible apple cultivars and rootstocks, and inoculated with several E . amylovora strains in order to study the genetics and mechanism of its fire blight resistance and susceptibility. A strong resistance QTL was first mapped on linkage group 3 (LG3) of M . × robusta 5 using an F1 progeny derived from a cross with the apple cultivar ‘Idared’ in Germany. This QTL was confirmed in two other F1 populations derived from crossing M . × robusta 5 with the rootstock ‘Malling 9’ in New Zealand, and with ‘Ottawa 3’ in the USA. A second QTL on LG7 was detected in the ‘Idared’ × M . × robusta 5 population but only with strains that break the LG3 QTL. However, in the US population of ‘Ottawa 3’ × M . × robusta 5, the LG7 QTL was detected regardless of strain-specificity, unlike in the New Zealand population of ‘Malling 9’ × M . × robusta 5 where the LG7 QTL was not also detected. Here, we report the detection of the LG7 QTL in a different ‘Malling 9’ × M . × robusta 5 population in Germany, and confirm the independence of the LG7 locus to E. amylovora strains.