Biological and Chemical Characterization of Musa paradisiaca Leachate

Abstract

There is a growing demand for molecules of natural origin for biocontrol and biostimulation, given the current trend away from synthetic chemical products. Leachates extracted from plantain stems were obtained after biodegradation of the plant material. To characterize the leachate, quantitative determinations of nitrogen, carbon, phosphorus, and cations (K⁺, Ca²⁺, Mg²⁺, Na⁺), Q2/4, Q2/6, and Q4/6 absorbance ratios, and metabolomic analysis were carried out. The potential role of plantain leachates as fungicide, elicitor of plant defense, and/or plant biostimulant was evaluated by agar well diffusion method, phenotypic, molecular, and imaging approaches. The plant extracts induced a slight inhibition of fungal growth of an aggressive strain of Colletotrichum gloeosporioides, which causes anthracnose. Organic compounds such as cinnamic, ellagic, quinic, and fulvic acids and indole alkaloid such as ellipticine, along with some minerals such as potassium, calcium, and phosphorus, may be responsible for the inhibition of fungal growth. In addition, jasmonic, benzoic, and salicylic acids, which are known to play a role in plant defense and as biostimulants in tomato, were detected in leachate extract. Indeed, foliar application of banana leachate induced overexpression of LOXD, PPOD, and Worky70-80 genes, which are involved in phenylpropanoid metabolism, jasmonic acid biosynthesis, and salicylic acid metabolism, respectively. Leachate also activated root growth in tomato seedlings. However, the main impact of the leachate was observed on mature plants, where it caused a reduction in leaf area and fresh weight, the remodeling of stem cell wall glycopolymers, and an increase in the expression of proline dehydrogenase.

Keywords: Basic Substance; PNPP; SNUB; biostimulant; fulvic acids; fungistatic activity; indole alkaloids; organic and inorganic salts; plant elicitor.

Figure 1

Diameter of inhibition zone of C. gloeosporioides in mm for freeze-dried leachate at 0.5, 1, 2, and 5 mg·mL⁻¹ and controls after 24 h and 1 week. Bars represent means and error bars are standard deviation. Treatments without common superscript letters (a, b, c, or d) differ significantly based on the Kruskal–Wallis Test with Dunn’s multiple comparison test.

Figure 2

Effect of leachate application on tomato seedlings in in vitro assay (A) and mature plants in phytotron assay (B) growing under drought stress. The color squares differ significantly based on the Mann–Whitney Test. In green, a significant increase compared to the control; in red, a significant decrease compared to the control; in gray, not significant. Percentages in squares correspond to leachate-induced increase or decrease compared to the control (water). Values on the right correspond to the different measurements and the p-value according to the Mann–Whitney Test. For the in vitro assay, each condition was replicated in three independent biological replicates with 90 seedlings in each replicate. For phytotron assay, each condition was replicated in four independent biological replicates with 15 plants in each replicate. ns: not significant.

Figure 3

Effect of leachate application under drought stress on cell wall imaging in in vitro and phytotron assays. The color squares differ significantly based on the Mann–Whitney Test. In green, a significant increase compared to the control; in red a significant decrease compared to the control; in gray, not significant. Percentages in squares correspond to leachate-induced increase or decrease in glycopolymers epitopes detection. (Z1) zone 1: epidermis + peridermis + collenchyma; (Z2) zone 2: cortical parenchyma; (Z3) zone 3: sclerenchyma + xylem + phloem; (Z4) zone 4: medullar parenchyma. Each condition was replicated was replicated in three independent biological replicates. ns: not significant.