The Allelopathic Potential of <i>Conocarpus lancifolius</i> (Engl.) Leaves on Dicot (<i>Vigna sinensis</i> L.), Monocot (<i>Zea mays</i> L.) and Soil-Borne Pathogenic Fungi

Abstract

Aqueous leaf extract and pulverized leaf tissue were tested for allelopathic effects on seed germination, seedling growth traits and net photosynthesis of corn ( Zea mays L.) and bean ( Vigna sinensis L.) The chemical constituents of the leaf extract were determined by GC-MS and the efficacy of the leaf extract to control some soil-borne fungal pathogens was also evaluated. The leaf extract inhibited germination, radicle and plumule lengths, root and shoot growth, chlorophyll content, photosynthesis and nutrient uptake in both crops. In corn and bean plants growth inhibition was proportional to the concentrations of the extracts (2.5% - 7.5%). Seed germination was associated with water uptake and the solute potential of the extracts. Leaf extracts also reduced of chlorophyll content, and stressed photosynthetic function by reducing photochemical efficiency (Fv/Fm) and electron transport rate (ETR) of PS II in corn and bean plants. Corn was more tolerant to the leaf extract than bean plants. The GC-MS analysis detected thirty one and thirty three compounds in winter and summer leaf extracts, respectively. The majority was phenolic compounds. Mycelia growth of Fusarium oxysporum f. sp. lycopersicon , Sclerotinia sclerotiorum , and Rhizoctonia solani was inhibited and in 10% extract the fungi died. The extract however, had no effect on Trichoderma harzianum . Leaf extract of C. lancifolius exhibited both herbicidal and fungicidal properties but cannot be recommended for biological control of soil borne fungal plant pathogens because it has the potential to physiologically stress or damage cultivated plants or crops.