|MGBECHI-EZERI, JOSEPHINE - Washington State University|
|ORAGUZIE, NNADOZIE - Washington State University|
|JOHNSON, KENNETH - Oregon State University|
Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2017
Publication Date: 6/24/2017
Citation: Mgbechi-Ezeri, J., Oraguzie, N., Porter, L., Johnson, K.B. 2017. Assessment of sweet cherry (Prunus avium L.) genotypes for response to bacterial canker disease. Euphytica. 213:145. doi: 10.1007/s10681-017-1930-4.
Interpretive Summary: Bacterial canker is a major disease impacting cherry growers world wide. It is caused by the bacterium Pseudomonas syringae pv. syringae. Copper sprays have mostly been used to manage this disease but antibiotics have also been used. Concerns over developing antibiotic-resistant strains that could have negative impacts on human health have lead to banning the use of antibiotics to manage this pathogen in commercial orchards. The most economical and environmentally safe approach to managing this pathogen is to develop cherry cultivars with resistance to the pathogen. The present research determined that the best innoculation technique to assess cherry lines with resistance to bacterial canker is to inoculate young shoots with the pathogen and measure the advancement of the disease through the tissue. This research also evaluated differences in susceptibility between different cherry tissue types such as fruit and leaves and found that fruits are more susceptible to infection and spread of the disease than leaf tissue and that fruits and leaves respond differently to infection. This research further identified cherry cultivars and breeding lines with excellent resistance to bacterial canker and powdery mildew diseases that can be used in breeding programs in the future to improve host resistance.
Technical Abstract: Integration of alleles for resistance into new cultivars requires information on the sources of resistance in the germplasm. This study was designed to compare: the efficacy of three inoculation methods (carborundum, mid-rib and shoot), the correlation between the susceptibility of fruit versus leaf tissue, and also the correlation between bacterial populations and symptom expression. Four market-leading cherry cultivars: Sweetheart, Bing, Regina and Chelan, and advanced selections: ‘AA’, ‘BB’, ‘CC’, ‘DD’, ‘EE’, ‘GG’, and their parents, ‘PMR-1’(powdery mildew resistant ) from Washington State University’s Sweet Cherry Breeding Program and Rainier were used in the study. Disease ratings were taken 2 to 8 days post- inoculation for carborundum and mid-rib inoculations, and at 8 weeks for the shoot method based on a 0-4 scale, where, 0=no necrosis and 4=total necrosis. The mean necrotic lesion lengths of ‘Rainier’ (57.2 mm), ‘Sweetheart’ (58.9 mm) and ‘Bing’ (53.8 mm) for shoot inoculations were significantly (p < 0.05) greater than that of ‘Chelan’ (46.5 mm) and ‘Regina’ (28.7 mm), while the advanced selections, as well as their parent, PMR-1, were not significantly different (p < 0.05). There was low correlation (r=0.37) between fruit and leaf foliage in disease response, and moderate correlation (r=0.50) between bacterial populations and disease symptoms expressed by the genotypes. Shoot inoculation is preferred for evaluation of genotypes for disease response. Disease severity values for Rainier’, ‘Sweetheart’, and ‘Bing’ were high, while severity values on ‘Regina’ and ‘Chelan’ were moderate and the advanced selections as well as PMR-1 had low disease severity values.