Natural Bioactive Substances in Fruits of Aronia melanocarpa (Michx.) Elliott Exposed to Combined Light-Type, Chitosan Oligosaccharide, and Spent Mushroom Residue Treatments

Greenhouse culture is a practical approach to obtain non-wood forest products from berry fruit at a higher efficacy than resource silviculture in natural understory. In this study, three-year old black chokeberry (Aronia melanocarpa (Michx.) Elliott 1821) seedlings were transplanted to a greenhouse where sunlight was complemented by red- (69.4% red, 30.2% green, 0.4% blue) and blue-color (15.3% red, 64.9% green, 19.8% blue) light-emitting diode (LED) illuminations. Half of the planting soils were amended by spent mushroom residue (SMR) (not amendment as the control) and half the seedlings were sprayed by chitosan oligosaccharide (CO) on leaves. All treatments can increase seedling height, but only blue light reinforces the basal diameter growth. Compared to sunlight, exposure to blue light can promote leaf nitrogen and phosphorus concentrations, superoxide dismutase activity, and fruit proanthocyanidin content. The combination with CO addition will further increase chlorophyl a content, acid phosphatase activity, and total phenolics in fruit. SMR amended can induce the steady state uptake of nutrients but failed to impact fruit quality. Overall, we recommend the combination of blue light LED illumination plus CO addition to culture black chokeberry for the purpose to gain natural bioactive compounds.