Antifungal effect of aqueous and ethanolic extracts of neem leaves, stem bark and seeds on fungal rot diseases of yam and cocoyam

Abstract

Background: Fungal rot diseases of white yam (Discorea rotundata) tubers and cocoyam (Colocasia esculenta) are the major post-harvest challenges in the availability of these root tubers. The use of biological extract of plants will prevent post-harvest losses without any negative health challenge. Methods: Microwave-assisted method of extraction was used for both aqueous and ethanolic extracts of neem samples. Fungal-rotted yam and fungal-rotted cocoyam samples were collected, and fungi from them were cultured on potato dextrose agar (PDA). The same medium was used for subculturing until pure fungal isolates were obtained. Pathogenicity tests were carried out on the yam and cocoyam tubers by inoculating with isolated fungi. The neem extracts were integrated into the PDA and their antifungal effects examined. Results and discussion: From the yam, Aspergillus ochareus, Sclerotium rolfsii and Lasidiodiplodia theobromae were isolated, while Aspergillus niger, Aspergillus oryzae and Rhizopus stolonifer were isolated from cocoyam samples. After 14 days of inoculation, isolated fungi were shown to be highly pathogenic except R. stolonifer and A. ochareus, which showed moderate pathogenicity. All the plant extracts showed antifungal activities at varied percentage mean zones of inhibition. The inhibition against fungal growth from the isolates of the rotted cocoyam gave mean inhibition between 39.53 ± 8.39% and 96.76 ± 1.60%. Except for ethanolic stem bark extract which gave 39.53 ± 8.39% limited zone of inhibition against A. niger growth, the rest of the extract exhibited good zones of inhibition against cocoyamisolated fungi ranging between 72.87 ± 3.55 and 96.79 ± 1.60%. On fungal isolates from yam, the mean percentage zones of inhibition of all extracts of the neem plant parts showed more effectiveness than the positive control (Ketoconazole) against L. theobromae growth. Aqueous stem bark extract with 93.80 ± 1.78% zone of inhibition showed comparable effectiveness to the control (100% inhibition) against A. ochareus growth, while against S. rolfii growth, there was good inhibition by all the extracts though not to the extent as that of the control. Conclusion: The fungitoxic potential of these plant extracts on rot-inducing fungi of stored yam and cocoyam suggests that the above extracts used in this study can be put to use by farmers as alternative to commercial/synthetic fungicides.

Use of Neem leaves as soil amendment for the control of collar rot disease of chickpea

“…In their study, soil amendment with Neem was also observed to be effective in enhancing the plant size and seed germination with minimum seedling mortality by F. oxysporum. Ezeonu et al (2018) also gave similar report regarding the effectiveness of Neem seed, bark, and leaf ethanolic extracts against fungal pathogens namely, Aspergillus oryzae, A. niger, Rhizopus stolonifer, A. ochraceus, and Lasiodiplodia theobromae responsible for rot diseases in cocoyam and yam plants. Obtained results agree with the findings of Ali et al (2017b) who discovered that nano emulsions of Neem represent excellent antifungal activity against many phytopathogenic fungi such as follows: S. rolfsii and Rhizoctonia solani that cause collar rot, dampingoff, wilting, and dry root rot under field conditions.…”

Plant extracts in agriculture and their applications in the treatment of seeds

“…The genera Acacia sp., Brassica sp. and the species Melia azedarach L., Rosmarinus officinalis L. and Zingiber officinale R. were identified in 2.48% 11.94 FEREIRA et al, 2014;ZAKA et al, 2019;FREIRE;SANToS, 2018;HASSAN et al, 2013;KUMAR et al, 2012;PARMAR, 2013;KUMAR et al, 2011;NAHAR;SHAMSI, 2020;NNEDINMA et al, 2019;ARSHAD et al, 2019;AL-SAMARRAI et al, 2012;JALEEL et al, 2020;AHMED et al, 2019;MEENA et al, 2020;FIAZ et al, 2012;PoDERoSo et al, 2016;ATRI;TIWANA, 2019;MAHMUD;HoSSAIN, 2017;REHMAN et al, 2019;TANVEER et al, 2016;GARCIA et al, 2019;HUSSAIN et al, 2015;EZEoNU et al, 2018;DA SILVA et al, 2014 BETTIoL., 2020;SHAPIRo-ILAN et al, 2013;KHAN et al, 2020;MUNoZ;QUILoDRAN;NAVIA, 2014 CHAND et al, 2016;TANVEER et al, 2016;SALJoQI et al, 2012;SIDDIQUE et al, 2019;ALSAHLI et al, 2018;HAN et al, 2018;FU et al, 2018.…”

Comparative bioactive compounds and fourier transform infrared spectroscopic evaluation of Azadirachta indica extracts and its potential as bio-fungicides against plant pathogenic fungi

“…A broad diversity of fungi genera are attack on vegetables and fruits, which creates quality issues connected to many aspects such as limited shelf life, organoleptic characteristics, dietary values and a results a huge economic loss (Diaz et al, 2011). The application of plants extracts for the diseases management of crops and plants poses little environmental risk and economically viable;, the herbs are accessible to the growers in the tropics, developing countries and numerous areas of the globe that have no easy reach to the synthetics pesticides (Chukwuma et al, 2018). The extracts of plants derived from stem, rhizome, fruits, flowers, roots, leaves and bark consist of numerous bioactive substances that have antifungal and antimicrobial properties (Kanal, 2021).…”

“…These functional groups reported antibacterial and antifungal potential (Basir and Javid, 2013;Javid et al, 2015). Although several studies have evaluated the phytochemicals, FTIR and antimicrobial activities of neem extracts against a broad range of pathogens (Ali et al, 2022;Amadioha, 1999;Chukwuma et al, 2018;Govindachari et al, 1998;Khanal, 2021;Khajista, 2013;Lethika et al, 2013;Nwali et al, 2018;Oyekanmi et al, 2021), but the antifungal activity against the plant pathogenic fungi and FTIR measurements together of neem extracts remains elusive. The current study was aim to find a plant product, which can be used as a substitute of commercially available chemical fungicide.…”