Effects of Extracts from Two Combretaceae Anogeissus leiocarpus (DC) Guill. and Perr. and Terminalia macroptera Guill. and Perr. on the Pseudomonas aeruginosa PAO1 Pathogenicity in Nicotiana tabacum L.

Aims: This study aimed to assess the ability of methanolic bark extracts from medicinal plants, Anogeissus leiocarpus and Terminalia macroptera for reducing Pseudomonas aeruginosa PAO1 bacteria pathogenicity in Nicotiana tabacum.

Study Design: A complete randomized block design was used with 3 replications including 3 infiltrations modes: PAO1 only, PAO1+ A. leiocarpus extract, PAO1+ T. macroptera extract; the control plants didn’t received infiltration.

Place and Duration of Study: The study was conducted at the Laboratory of Biochemistry and Chemistry Applied and Plant Ecophysiology Laboratory, University Joseph KI-ZERBO between November 2018 and May 2019.

Methodology: Six weeks old tobacco plants previously cultured in vitro were infected via infiltration of bacterial inoculum with or not plant extract into Arabidopsis leaves. Ten days after the infection, phenotypic and biochemical leaves parameters were evaluated. The ImageJ software was used to measure discolored and necrotic surfaces. Chlorophyll a and b, proteins, total polyphenols and total flavonoids foliar contents were determined by spectrophotometry.

Results: The extracts of plants used reduced significantly the severity of chlorosis and necrosis. They also allowed to increase the chlorophyll a but lowered the total flavonoids contents. T. macroptera extract showed an important reduction potential of necrotic area and total flavonoid content, and led to a decrease of total polyphenol content. A. leiocarpus extract application improved the protein content.

This antibacterial activity seems attributable to the content in secondary metabolites including polyphenols acting alone or in synergy with those synthesized by tobacco. In addition, it appears that i) total polyphenols content make T. macroptera the most effective extract plant on foliar necrosis and that ii) perhaps other(s) class(es) of extract polyphenol, different of flavonoids, is (are) involved in the protective action on leaf 10 days after infection.

Conclusion: A. leiocarpus or T. macroptera extracts in the inoculum reduced chlorosis and necrosis damages thanks to infiltrated polyphenols but not enough to prevent damages completely.