Aims: To extract, identify and evaluate in vitro the antifungal activity of the phytochemical groups of Ageratum conyzoides and Newbouldia laevis on the strain of Lasiodiplodia theobromae. Study Design: Exploitation of medicinal plants to combat the growth of L. theobromae, responsible for the decline of cocoa cultivation. Location and Duration of Studies: Faculty of Sciences, University of Kisangani, between April 2017 and February 2018. Methodology: The crude extracts of the dry leaves of A. conyzoides and N. laevis were tested (at 100 mg/mL). Potato dextrose agar was used as the culture medium. After chemical screening, abundant phytochemical groups were isolated and tested. Results: The aqueous, 95% ethanolic and ethereal crude extracts of A. conyzoides are more antifungal (respective percentages of inhibition PI: 80.74; 84.10 and 85.64%) than those of N. laevis (63.28; 72.64 and 75.23%). The minimum inhibitory concentration (MIC) of the aqueous crude extract of A. conyzoides is lower (25 mg/mL) than that of the ethanolic extract (50 mg/mL). Tannins are very abundant in A. conyzoides and in N. laevis. Saponins, sterols and terpenes are abundant in both plants. The extraction yields of tannins and saponins are respectively 20.67 and 2.43% in A. conyzoides and 10.47 and 2.38% in N. laevis. A. conyzoides contains the gallic tannins while N. laevis, the condensates and catechics. The saponins and tannins of A. conyzoides are more antifungal (respective PI: 84.40 and 54.44%) than those of N. laevis (PI: 75.56 and 32.96%). Discussion: The saponins of A. conyzoides and N. laevis are more active on the strain of L. theobromae than the tannins. Saponins are surfactants that can destabilize membrane structure of microorganisms including fungi. Conclusion: The saponins of the two plants have shown a very interesting antifungal power on the strain of L. theobromae. The identification of their active molecules is ongoing.

Aims: To determine the chemical composition of essential oil of Ageratum conyzoides with antifungal activity on the strain of Lasiodiplodia theobromae in the Kisangani region. Location and Duration of Studies: Faculty of Sciences of University of Kisangani (Democratic Republic of Congo) and Faculty of Biosciences Engineering of University of Ghent (Belgium), between May to November 2019. Methodology: The essential oil from the leaves of A. conyzoides was extracted by hydrodistillation. Potato dextrose agar (PDA) was used as a culture medium. In vitro evaluation of its antifungal activity was performed on PDA medium and expressed as percentage of inhibition (PI). Results: The extracted essential oil (with a yield of 0.63%) showed a PI of 91.63% on the strain of L. theobromae after two days of incubation. It consists of at least 23 compounds, of which seven are in the majority (abundances greater than 1.5% and represent 92.05%), namely Precocene I (38.33%), Beta-caryophyllene (26.51%), Beta-sesquiphellandrene (8.63%), Beta-cubebene (7.91%), Alpha-muurolene (4.95%), 1.5.9.9-Tetramethyl-1.4.7-cycloundecatriene (3.04%), Cis-beta-farnesene (2.99%). The hydrocarbon sesquiterpenes are the most frequent compounds (58.95%). Discussion: Compared to the A. conyzoides saponins the PI obtained from the essential oil is higher. The essential oil chemotype obtained from the leaves of A. conyzoides is of the Precocene I type, similar to the oils from the stems and flowers of the same plant in West Africa. Conclusion: The essential oil of A. conyzoides has a very high inhibitory power on L. theobromae. It mainly contains the Precocene and the hydrocarbon sesquiterpenes. Assessment of the antifungal activity of each separate molecule should be considered.

The largest genetic diversity of plantain banana (Musa AAB subgroup) is found by DRCongo. Arbuscular mycorrhizal fungi (AMF) are synergistic beneficial organisms with a positive effect on growth vigor. We determined the influence of plantain banana-based agrosystems on the diversity of AMF in agroforestry and home-garden field systems located in the Kisangani region of DR Congo. Soil samples of the different agrosystems showed a high mycorrhizal frequency (82.5%) with an overall mycorrhizal rate of 33.43%. Vigorous plantain plants are growing in soils that rich in AMF spores whereas non vigorous ones were found in soils that had few AMF spores. There were also significant differences between cultivars, in terms of the number of spores. Glomus was the most abundant genus followed by Gigaspora, Acaulospora, Scutellospora and Entrophospora. The diversity indices evaluated, richness, abundance and Shannon_H showed non-significant difference between agroforestry and home-garden plantains. However, agroforestry plantains showed a larger Inv-Simpson and Equitability-J index than home-garden plantains. Soil physico-chemical characteristics had an effect on abundance of mycorrhizal genera in all inventoried mycorrhizal taxa.

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The microorganisms play crucial roles in the cycle of matter and damage the organic substances, sources of electrons, source of carbon, and source of energy for their biosynthesis. In this work, we studied the impact of the aerobic mesophiles microorganisms on the black sigatokaof banana in the old secondary forest. The objective was to count and to identify the microbial diversity of the forest ecosystems, as well as to study their impact on the development of the black sigatoka of banana. The assessment of the microbial populations has been done in an experimental field according to a device in blocks of Fischer by the method of successive dilutions of coloration of Gram and by the discharge of ascospores. The results showed that the rain season was lower in total microbial biomass (700, 7 colonies) than subdry season (840,3 colonies). The Bacillus genera have been more represented more than the Coccusgenera. The impact of black sigatoka of banana was raised at the cultivar LibangaLikale (40%) and low at Yangambi 5 Km (14%). The distribution of microorganisms in depth in the sub-dry season to the level of surface with vegetation was considerable either 3819, 3. 10 3 UFC(UNIT FORMAT COLONY) by gram of soil between 0 and 5 cm against 2754,5.10 3 UFC by gram of soil between 15 and 20 cm. This suggests that the raised number of microorganisms could have positive impact on soil fertility by decreasing the illnesses in this ecosystem.