Abstract
Bacterial canker is a major disease of stone fruits and is a critical limiting factor to sweet cherry (Prunus avium) production worldwide. One important strategy for disease control is the development of resistant varieties. Partial varietal resistance in sweet cherry is discernible using shoot or whole tree inoculations; however, these quantitative differences in resistance are not evident in detached leaf assays. To identify novel sources of resistance to canker, we used a rapid leaf pathogenicity test to screen a range of wild cherry, ornamental Prunus species and sweet cherry × ornamental cherry hybrids with the canker pathogens, Pseudomonas syringae pvs syringae, morsprunorum races 1 and 2, and avii. Several Prunus accessions exhibited limited symptom development following inoculation with each of the pathogens, and this resistance extended to 16 P. syringae strains pathogenic on sweet cherry and plum. Resistance was associated with reduced bacterial multiplication after inoculation, a phenotype similar to that of commercial sweet cherry towards nonhost strains of P. syringae. Progeny resulting from a cross of a resistant ornamental species Prunus incisa with susceptible sweet cherry (P. avium) exhibited resistance indicating it is an inherited trait. Identification of accessions with resistance to the major bacterial canker pathogens is the first step towards characterizing the underlying genetic mechanisms of resistance and introducing these traits into commercial germplasm.
Highlights
Plant diseases caused by bacteria remain problematic for the global horticultural industry due to a lack of effective control measures (Sundin et al, 2016)
Bacterial canker is a major disease of stone fruits and is a critical limiting factor to sweet cherry (Prunus avium) production worldwide
To identify novel sources of resistance to canker, we used a rapid leaf pathogenicity test to screen a range of wild cherry, ornamental Prunus species and sweet cherry × ornamental cherry hybrids with the canker pathogens, Pseudomonas syringae pvs syringae, morsprunorum races 1 and 2, and avii
Summary
Plant diseases caused by bacteria remain problematic for the global horticultural industry due to a lack of effective control measures (Sundin et al, 2016). This partial resistance seen in woody tissues is probably quantitative, involving multiple alleles having small effects, with the most resistant varieties still succumbing to disease under favourable conditions Only partial, such resistance could be highly useful for Prunus breeding as it could reduce overall pathogen load in orchards as part of an integrated disease management approach (Sundin et al, 2016). Progress towards understanding the genetic factors involved in bacterial canker resistance has been made by Omrani et al (2019) who identified quantitative trait loci (QTLs) involved in partial resistance in apricot These loci contain genes involved in phytohormone signalling, a process known to play a pivotal role during the plant immune response. Our results have identified potential sources of resistance to members of each of the pathogenic clades of P. syringae
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