Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2017
Publication Date: 5/1/2017
Citation: Sun, J., Janisiewicz, W.J., Evans, B.E., Jurick II, W.M., Chen, P. 2017. Composition of phenolic compounds in wild apple with multiple resistance mechanisms against postharvest blue mold decay. Postharvest Biology and Technology. 127:68-75.
Interpretive Summary: Apple production is based on many commercial cultivars with limited resistance to various diseases and pests, and adaptation to environmental stresses. Resistance against the fungus causing blue mold decay of apples declines quickly as the fruit matures, and there is practically no resistance at harvest. Recently, resistance to blue mold was found among wild apples from Kazakhstan and other parts of the world, and there are indications that preexisting substances are involved in the resistant mechanism. We determined the composition of phenolic compounds in the resistant and susceptible apples. The resistant apples had distinctly different phenolic compositions from the susceptible apples, which supports the hypothesis of the possible relationship between the phenolic content of wild apples and their resistance to blue mold. Findings from this study may be used by breeders in evaluating crosses for resistance to blue mold and may be helpful in further defining apple defense mechanism(s) against fungus causing blue mold.
Technical Abstract: Several wild apple accessions (Malus sieversii) from Kazakhstan and two (Malus × soulardii, Malus sylvestris) from other parts of the world are highly resistant to blue mold decay caused by Penicillium expansum. Previous studies on the wound responses of these apples to infection by this fungus suggest multiple mechanisms of resistance including innate immunity. In this study, the phenolic compositions of extracts from mature wild apples resistant (GMAL 4317.f, PI 589391, and PI 369855) and susceptible (GMAL 3623.i) to blue mold, as well as the susceptible cultivar ‘Golden Delicious’ (Malus × domestica) were investigated using ultra-high-performance liquid chromatography coupled to diode array detection and high resolution multiple stage mass spectrometry. The metabolomic and quantitative results of this study support the hypothesis of the possible relationship between the phenolic content of wild apples and their resistance to P. expansum. Apple accessions resistant to P. expansum had higher concentrations of procyanidins, dihydrochalocone, flavonols, and hydroxycinnamic acids. Findings from this study may lead to the development of physiological markers of resistance that could be used by breeders in evaluating crosses for resistance to blue mold and may be helpful to further define apple defense mechanism(s) against P. expansum.