Abstract
In this research study potential synergistic action of aqueous extracts of olive-pomegranate-orange fruits isolated by microwave assisted extraction were investigated as biocontrol agents against several plant pathogenic fungi. The aim of the research study was the production of mixed liquid extracts to be used as natural phytoprotective agents in organic farming. The results proved that the use of 100%-pure olive fruit polyphenol extract affected the mycelium growth of B. cinerea, V. dahliae, R. solani, E. lata, M. laxa, P. lycopersici and P. punicae. However, it did not affect the mycelium growth of F. oxysporum f. sp., lycopersici, A. niger, and G. graminis. Moreover, pomegranate polyphenol extract at 100% concentration inhibited mycelium growth of B. cinerea. Various olive-pomegranate-orange polyphenol aqueous extract combinations may be used in order to control the mycelium growth of the majority of the tested microorganisms. However, the use of any combination and concentrations of the tested samples (1-72) did not affect the mycelium growth of F. oxysporum f. sp., lycopersici, A. niger, and G. graminis thus, their use as biological control agent is not recommended. According to the findings of the present research, it can be suggested that the olive fruit polyphenol extract be used as potential biocontrol agent, in order to stimulate mycelium growth of various plant pathogenic fungi.
Highlights
The increase in the human population as a result of the improvement of the standard of living results the intensification of food processing and the problematic disposal of organic-agri-food waste in the environment.The agri-food processing sector, in the Mediterranean region, produces large volumes of waste with a high organic load, rich in polyphenols
"black mold" on certain fruits and vegetables and produces important potent mycotoxins called ochratoxins, Gaeumanomyces graminis a plant pathogen that produces extensive damage on the sheath of rice, causing black spots, Rhizoctonia solani a wide host range and worldwide distribution soil borne pathogen that attacks its hosts when they are in their early stages of development, such as seeds and seedlings, Eutypa lata and important plant pathogen on vines, Monillia laxa a plant pathogen that is responsible for the brown rot blossom blight disease that infects many different types of stone fruit trees, Pyrenochaeta lycopersici, which infects and causes damage to members of the families of Solanaceae and Cucurbitaceae causing brown lesions on the surface of medium roots and Phoma punicae a common soil borne pathogen
Samples 28 and 68 containing up to 90% olive polyphenol mixed with pomegranate and orange reduced the growth of F. oxysporum mycelium
Summary
The increase in the human population as a result of the improvement of the standard of living results the intensification of food processing and the problematic disposal of organic-agri-food waste in the environment.The agri-food processing sector, in the Mediterranean region, produces large volumes of waste with a high organic load, rich in polyphenols. By-products of agri-food processing have high management costs and may contaminate the environment when disposed out without any treatment These by-products often hide a small "treasure", since they contain rich amounts of natural antioxidant, antimicrobial and bioactive substances that can be isolated and recovered from these wastes. The aforementioned approach is an EU guideline under the term of bio-refinery which means the gradual full utilization of solid waste for the production of a range of valuable materials This approach leads to a reduction in the carbon footprint of solid waste due to its full utilization and its re-introduction into the food chain either directly as antimicrobial or antioxidant food additives or indirectly as eco-plant protection materials. The synergy of the produced bio-functional substances may further increase their potency especially in microbiostatic or microbicidal activity according to the well-known theory of multiple barriers [1]
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