PG Thesis

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    Copper nanoparticles green synthesized using leaf extract of Piper colubrinum for the management of foot rot disease in black pepper (Piper nigrum L.)
    (Department of Molecular Biology and Biotechnology, College of Agriculture, Vellayani, 2025) Aashima Rahim.
    The study entitled " Copper nanoparticles green synthesized using leaf extract of Piper colubrinum for the management of foot rot disease in black pepper (Piper nigrum L.)" was conducted at College of Agriculture, Vellayani during 2023-24. The objectives of the study were green synthesis of copper nanoparticles using leaf extracts of P. nigrum, P. colubrinum (foot rot-resistant,) their characterization; testing the efficacy of these copper nanoparticles in managing foot rot disease in black pepper caused by Phytophthora capsici. Copper nanoparticles (CuNPs) were synthesized using leaf extracts of P. nigrum and P. colubrinum for the management of foot rot of black pepper. The CuNPs from P. nigrum characterized using UV-visible spectroscopic analysis, X-ray diffraction patterns, and FTIR spectrum revealed an absorption spectrum typical of copper nanoparticles at 800 nm, the cubic lattice structure of copper nanoparticles and distinct characteristic bands at 3315.28 and 1635.50 cm-1. The CuNPs synthesized using P. colubrinum leaf extract had an absorption spectrum typical of copper nanoparticles at 800 nm, the cubic lattice structure of copper nanoparticles with prominent characteristic bands at 3264.52 and 1636.62 cm-.1. Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) revealed that CuNPs synthesized using both P. nigrum and P. colubrinum had sizes 59.86 and 64.52 nm, respectively. The pathogen was isolated and identified as P. capsici followed by proving the pathogenicity. In vitro bioassay (poisoned-food assay) demonstrated significant inhibition of the mycelial growth of pathogen when treated with green synthesized CuNPs using leaf extract of P. colubrinum (PC-CuNPs) at concentration 250 and 500 ppm. PC-CuNPs showed the highest per cent inhibition (PI) against P. capsici compared to those synthesized using P. nigrum leaf extract (PN-CuNPs) and commercial copper nanoparticles (C-CuNPs). The mycelial inhibition of 90% and 92% was exhibited by green synthesized PC- CuNPs in PDA medium amended with 250 ppm and 500 ppm, respectively. Thus, the green synthesized PC- CuNPs at 500 ppm had the maximum inhibition, significantly higher than the chemical control. Mycelial inhibition was absent in treatments with leaf extracts alone. Detached leaf assay was performed on black pepper leaves sprayed with the green synthesized PC-CuNPs, followed by challenge inoculation of the pathogen. The treatment reduced lesion development when compared to leaves treated with green synthesized CuNPs from P. nigrum (PN-CuNPs), C- CuNPs and both leaf extracts. Leaves treated with green synthesized PC-CuNPs at 250 ppm failed to develop symptom after three days of inoculation when compared to the other treatments. In vivo experiment gave results similar to in vitro studies. Application of GSCuNP from P. colubrinum at 250ppm deferred the symptom development in the varieties of black pepper viz., Karimunda, Panniyur-1. While the application of leaf extract of P. nigrum and P. colubrinum alone was ineffective in managing the disease. CuNPs synthesized using leaf extract from disease-resistant P. colubrinum at 250ppm effectively suppressed foot rot disease incidence in susceptible black pepper varieties. This study pioneers the demonstration of enhanced pathogen-suppression activity against Phytophthora capsici, a major pathogen of black pepper using copper nanoparticles green synthesized using the leaves of a disease-resistant Piper colubrinum genotype.